Bio266 exam 2

Adipocytes

(fat cells) - in many different connective tissues cytoplasm filled with a single large lipid inclusion

Long bones contain different populations of bone cells involved in maintenance of bone homeostasis just stating this

** notes Osteoprogenitor cells-stem cells Osteoblasts produce bone matrix Osteocytes mature bone cells and maintain bone matrix In order for skeleton to stay healthy it has to be regularly be remodeled- old bone tissue replace by new bone tissue Osteoblast- make new bone Destroy old bone- Monocyk line can produce osteoclast can produce enzymes and acids that can break down bone matrix

psuedostratified columnar epithelium

- appears layered because nuclei are at various heights; only one cell-layer thick with basal plasma membranes firmly in contact with basement membrane; in segments of respiratory tract and nasal cavity; ciliated

neuroglial cells

- diverse group of smaller cells; support activity of neurons: -Functions: -Anchoring neurons and blood vessels in place -Monitoring composition of extracellular fluid -Speeding up rate of nerve impulse transmission -Circulating fluid surrounding brain and spinal cord Able to divide by mitosis (unlike neurons)

sensation

- enables nervous system to perceive changes in body's internal or external surroundings; critical to homeostasis: ---Skin has numerous sensory receptors that detect changes in internal and/or external environment ---Receptors detect potentially harmful stimuli (heat, cold, and pain); could lead to tissue damage

Phagocytes

- immune system cells; ingest foreign substances, microorganisms, and dead or damaged cells by phagocytosis; include macrophages (resident or migrant) and neutrophils (migrant cells) Other immune system cells migrate in and out of connective tissues depending on body's needs

organic matrix

- known as osteoid; consists of protein fibers, proteoglycans, glycosaminoglycans, glycoproteins, and bone-specific proteins Collagen - predominant protein fiber; forms cross-links with one another; helps bone resist torsion (twisting) and tensile (pulling or stretching) forces Collagen fibers align themselves with hydroxyapatite crystals; enhances hardness of bone Glycosaminoglycans and proteoglycans create an osmotic gradient; draw water into osteoid; help tissue resist compression Glycoproteins in osteoid bind different components of osteoid and inorganic matrix together

Synovial membranes

- line cavities surrounding freely moveable joints (knee or shoulder); two connective tissue layers without layer of epithelial cells: -----Outer layer - usually composed of mixture of loose and dense irregular connective tissue ------Inner layer - synoviocytes (modified fibroblasts) secrete synovial fluid; watery, slippery fluid; primarily functions to lubricate joint

Nervous tissue

- makes up majority of brain, spinal cord, and nerves; two main cell types and their surrounding ECM Neurons - capable of sending and receiving messages Neuroglial cells - perform various functions; support neuron activities ECM is unique; ground substance with unique proteoglycans not found in other tissues; contains very few protein fibers

Trachea

- more complex organ; consists of many different tissue types -Hollow; provides passageway through which air passes on way into/out of lungs - illustration of tissues of trachea from superficial to deep with list of main functions -Each tissue layer serves an important role in overall function of trachea: conducting air

Reticular tissue

- mostly reticular fibers produced by fibroblasts (reticular cells) o Forms fine networks that support small structures such as blood and lymphatic vessels o Also in lymph nodes and spleen; forms weblike nets that trap old and foreign cells o Forms part of basement membrane; supports all epithelia and internal structure of liver and bone marrow

inorganic matrix

- predominantly calcium salts; bone stores around 85% of total calcium ions as well as large amount of phosphorus: Calcium and phosphorus salts exist as large molecules of hydroxyapatite crystal Crystalline structure makes bone one of hardest substances in body; strong and resistant to compression Allows bone to be both protective and supportive (demonstrates Structure-Function Core Principle) -Bicarbonate, potassium, magnesium, and sodium are also in inorganic matrix

exocrine glands

- release products onto apical surfaces of epithelium (external surface of body) or lining hollow organ (opens to outside of body): --Products, secreted from gland through epithelial-lined duct, have only local effects on cells in gland vicinity --Glands vary in complexity from single cells to large multicellular glands with branching ducts and many secretory units

cells of connective tissue proper

- resident cells permanently inhabit tissue; migrant cells migrate to areas of body depending on situation -Fibroblasts -Adipocytes -Mast cells -Phagocytes -Other immune system cells

membranes

- thin sheets of one or more tissues; line body surface or cavity: o Most consist of superficial epithelial layer resting on connective tissue layer; sometimes contain smooth muscle o Functions: anchor organs in place, serve as barriers, function in immunity, and secrete various substances o True membranes - serous and synovial membranes; fit above structural and functional definitions o Membrane-like structures - mucous and cutaneous membranes; don't fit above structural and functional definitions; perform many of same functions notes) Simplest organs— True membranes don't open to outside of body ex serous membrane or serosa

blood

- unique; ECM is fluid -Plasma proteins - not like fibers found in other connective tissues; smaller with a variety of functions, including transport of substances and blood clotting -Erythrocytes (red blood cells) bind to and transport oxygen throughout body -Leukocytes (white blood cells) function in immunity -Platelets - cell fragments; major role in blood clotting

dermis

-- highly vascular layer deep to epidermis Functions: -Provides blood supply for epidermis -Contains sensory receptors -Anchors epidermis in place Composed of two distinct layers; two types of connective tissue

Overall compact bone structure:

---Osteons are NOT permanent structures; osteoclasts break down and osteoblasts rebuild bone matrix depending on needs of bone or body; leaves behind characteristic features: ----------Interstitial lamellae -fill spaces between circular osteons; represent remnants of old osteons

bone

--ECM is about 35% organic components (collagen fibers and ground substance (osteoid)); --remaining 65% is inorganic calcium phosphate crystals, making bone one of the hardest substances in the body --Dynamic tissue capable of remodeling;

functions of epithelial tissue

--Protection - shield underlying tissues from mechanical and thermal injury --Immune defenses - form physical barriers; o prevent invasion by microorganisms; o specialized cells of immune system are scattered throughout epithelial tissues to protect underlying tissues --Secretion - form glands that produce substances like hormones and oils; secreted into blood or through ducts respectively --Transport into other tissues - selectively permeable membranes; substances are able to cross these barriers by passive or active transport and enter other tissues --Sensation - most associated with rich nerve supply; detect changes in internal and external environments; **taste buds are examples of specialized sensory epithelial cells

Four primary tissue types - defined by kind and number of cells, amount and composition of ECM, and specific functions:

-Epithelial tissues (epithelia) - tightly packed sheets of cells with no visible ECM; cover and line all body surfaces and cavities; specialized epithelia form glands that manufacture secretions (sweat, saliva, or chemical messengers (hormones) --Connective tissues - connect all other tissues to one another; ECM is a prominent feature for most connective tissue types; cells scattered throughout; bind, support, protect, and allow for transportation of substances ---Muscle tissues - capable of generating force by contracting; little ECM between cells ----Nervous tissues - capable of generating, sending, and receiving messages; cells that support this activity also within unique ECM

Proteoglycans

-GAGs bound to protein core (resembles bottle brush) o Thousands of proteoglycans bind to very long GAG (such as hyaluronic acid); form huge proteoglycan "aggregates" o Make ECM firmer, more solid, and resistant to compression o Form barrier to diffusion of substances through ECM; protect underlying tissue from invading microorganisms

Form of epidermis in various parts of body differs to match its function; Structure-Function Core Principle

-Palms of hand and sole of foot are subjected to great deal of mechanical stress -Remaining regions of skin are not subjected to as much stress -Differences in function and exposure to stress have led to thick and thin skin

ECM performs a variety of functions:

-Provides tissue with strength to resist tensile (stretching) and compressive forces --Directs cells to proper positions within tissue and holds those cells in place ---Regulates development, mitotic activity, and survival of cells in a tissue

layer continued.

-Stratum spinosum o thickest layer o on top of stratum basale o still close to blood supply o metabolically and mitotically active Stratum granulosum o Three to five layers of cells o prominent cytoplasmic granules with keratin bundles or lipid-based substance o secreted by exocytosis o Hydrophobic lipids provide waterproofing o maintains internal fluid and electrolyte homeostasis o leads to isolation and death of cells in layer and more superficial layers

stratified columnar epithelium

-also rare in humans -few layers -apical layer is columnar and basal cell layer is cuboidal -in male urethra, cornea of eye, and auction of certain glands such as salivary glands

nonkeratinized stratified squamous epithelium

-apical cellular layers retain nuclei; -still alive; -in regions subjected to mechanical stress where surface must remain moist; -mouth, throat, esophagus, anus, vagina

connective tissue consists of cells and ECM

-cells are surrounded by protein fibers and embedded in ground substance -ECM is a characteristic feature; plays extensive role in function of connective tissue type

Glycosaminoglycans (GAGs)

-chondroitin sulfate (small) and hyaluronic acid (enormous huge) o Negative charges of sugars in GAG attract positively charged ions in ECF o Ions create concentration gradient within ECF; draw water out of cells and blood vessels by osmosis o Effectively "trap" water in ECM; help ECM to resist compression; Gradients Core Principle

Smooth muscle tissue

-consists of smooth muscle cells; -contractions are involuntary like cardiac muscle: -In walls of nearly every hollow organ, blood vessels, eyes, skin, and ducts of certain glands -Flattened cells with one centrally located ovoid nucleus

Hypodermis - (superficial fascia or subcutaneous fat)

-deep to dermis -Not part of skin; anchors skin to deeper structures like muscle and bone -Made of loose connective and adipose tissues -has abundant blood supply

Sebaceous glands

-duct that empties into hair follicle or small pore; -make and secrete sebum: waxy, oily mixture of mostly lipids -Everywhere on body except palms and soles -greatest number on face and scalp -Secretion is influenced by sex hormones, especially male hormone (testosterone) -Dramatic increase in sebum production occurs after puberty; -Coats hair, providing it with hydrophobic barrier; inhibits water loss -Also inhibits growth of or kills certain bacteria

Accessory structures

-embedded in cutaneous membrane -sweat glands, sebaceous glands, hair, and nails -Skin contains sensory receptors and arrector pili muscles (small bands of smooth muscle associated with hair) -Epidermis is avascular: --Relies on diffusion of oxygen and nutrients from blood vessels in deeper dermis --limits epidermal thickness --Gradients Core Principle --About 50% of epidermal cells are too far from adequate blood supply to sustain life --superficial layers are made up entirely of dead cells

Stratified epithelium

-more than one layer of cells -best as protective barriers where subjected to high degrees of mechanical stress; types include keratinized stratified squamous epithelium - o apical cellular layers are dead o lack nuclei o filled with protein keratin (notes) Keratin is waterproof Fill cells up with it which waterproofs them and kills them Make up epithlium of epidermis Epithelial cells are dead

fibroblasts

-most common resident cells -Mature cells with properties of immature "blast" cell -Make protein fibers and ground substance (components of ECM) -continually produce collagen proteins

Skeletal muscle tissue

-mostly attached to skeleton; -contraction produces body movement : -Skeletal muscle must be stimulated by nervous system to contract; under voluntary (conscious) control -Most skeletal muscle cells (muscle fibers) are long, extending to almost entire length of whole muscle

Loose connective tissue, (areolar tissue)

-mostly ground substance -contains all three types of protein fibers, fibroblasts, and occasionally adipocytes, suspended in ground substance: o Beneath epithelium of skin, in membranes lining body cavities, and within walls of hollow organs o Contains and supports blood vessels vital to avascular epithelial tissues; o houses immune system cells

Dense connective tissue (fibrous connective tissue) -

-mostly protein fibers; three classes: 1. Dense irregular connective tissue - predominantly disorganized collagen bundles ---Strong; resists tension in all three planes of movement ---In high tension areas such as dermis (deep to skin) and surrounding organs and joints 2. Dense regular connective tissue -Organized into parallel collagen bundles -In tendons and ligaments; subject to tension in one plane of movement 3. Dense regular elastic connective tissue (elastic tissue) -Mostly parallel-oriented elastic fibers with randomly oriented collagen fibers -In walls of organs that must stretch to function (large blood vessels and certain ligaments) Note: arrangement of fibers in dense regular and irregular connective tissues is example of Structure-Function Core Principle

Cardiac muscle tissue

-only in heart -composed of cardiac muscle cells; -striated like skeletal muscle cells: -Involuntary - brain does not have conscious control over contraction -Cells are short, branched; usually only one nucleus (uninucleate)

transitional epithelium

-only in urinary system; -lines interior of kidney, ureters, urinary bladder, and urethra; -cuboidal basal cell layers and dome-shaped apical cell layers in relaxed tissue; -ability of apical cells to flatten allows tissues to stretch

stratified cuboidal epithelium

-rare in humans; -2 cell layers; -lines ducts of sweat glands

gap junctions

-small pores formed by protein channels between adjacent cells; allow small substances to flow freely between each cell's cytoplasm --In between cells that communicate with electrical signals (cardiac muscle cells) ---Gap junctions illustrate Cell-Cell Communication Core Principle

Dermal root sheath

-surrounds epithelial root -consists of connective tissue -supports follicle and keeps it separate from dermis Arrector pili muscles --small bands of smooth muscle --attach to dermal root sheath on one end and dermal papillary layer on other -Contraction of arrector pili causes hair to stand up (piloerection -gives skin dimpled appearance ("goosebumps")

Papillary layer

-thinner, most superficial of two layers -Loose connective tissue -Special collagen fibers at dermis-epidermal junction; extends into epidermal basement membrane; anchors epidermis to dermis Dermal papillae -tiny projections at surface of papillary layer where it contacts epidermis: -Contain tiny blood vessels (capillaries) arranged in loops -extend up into most superficial part of dermal papillae -Allow oxygen and nutrients to diffuse into extracellular fluid of dermis, then into avascular epidermis Tactile (Meissner) corpuscles -also in dermal papillae -sensory receptors -respond to light touch stimuli -more numerous where sensation is primary function (skin of fingertips, lips, face, and external genitalia)

cartilage

-tough, flexible tissue -absorbs shock and resists tension, compression, and shearing forces; -ECM consists of collagen and elastic fibers, proteoglycans, and glycosaminoglycans -Populated with two cell types: o Chondroblasts - immature cells; divide by mitosis and make most of ECM o Eventually surround themselves in small cavities (lacunae) in ECM to become mature, largely inactive chondrocytes - Essentially avascular, unlike most connective tissues; blood supply is limited to outer sheath (perichondrium) of dense irregular collagenous connective tissue - Oxygen and nutrients must diffuse from blood vessels in perichondrium through ECM to supply chondroblasts and chondrocytes; limits thickness of living cartilage

Three protein fiber types

1 collagen fibers- make up 20-25% of all proteins in body; --composed of multiple repeating subunits; form white fibrous protein; --resistant to tension (pulling and stretching forces) and pressure 2 Elastic fibers - composed of protein elastin surrounded by glycoproteins; --extensibility allows fibers to stretch up to one and a half times resting length without breaking; --once stretched, fibers return to resting length (elasticity) 3 Reticular fibers - thin, short collagen fibers; --form meshwork or scaffold that supports cells and ground substance of many tissues; --form weblike structure in organs such as spleen that helps trap foreign cells

other cells of the epidermis

1. Dendritic (Langerhans) cells: --in stratum spinosum --phagocytes of immune system --protect skin and deeper tissues from pathogens 2. Merkel cells --oval cells scattered throughout stratum basale; sensory receptors associated with small neurons in dermis: --Detect light touch and discriminate shapes and textures --Large numbers in regions specialized for touch: fingertips, lips, and at base of hairs 3. Melanocytes --in stratum basale --produce melanin (protein pigment ranging from orange-red to brown-black)

Functions of skeletal system

1.. Protection: certain bones (skull, sternum (breastbone), ribs, and pelvis) protect underlying organs 2. Mineral storage and acid-base homeostasis: bone is most important storehouse for calcium, phosphorus, and magnesium salts; minerals are also present in blood as electrolytes, acids, and bases; critical for electrolyte and acid-base maintenance 3. Blood cell formation: bones house red bone marrow - specialized connective tissue involved in formation of blood cells (hematopoiesis) ---all blood cells are made in bone marrow

Cartilage can be further divided into three classes by ECM composition:

1.Hyaline cartilage - most abundant cartilage - ECM mostly ground substance made of small bundles of fine collagen; gives tissue glossy bluish-gray appearance - On ends of bones in joints (articular cartilage), linking sternum to ribs, framing sections of respiratory tract, and in nose - Most of fetal skeleton is hyaline cartilage; replaced with bone during development ((NOSE)) --------- 2.Fibrocartilage filled with bundles of collagen fibers little room for ground substance in ECM Fibroblasts reside in tissue; also chondroblasts and chondrocytes; fill ECM with collagen and some elastic fibers Tissue has great tensile strength with some degree of elasticity In between bones of fibrous joints; forms articular discs that improve fit of bones in joints --------- Elastic cartilage - mostly elastic fibers in ECM --Allows tissue to vibrate --In limited number of structures; --external ear assists with detection of sound in air; --larynx assists with production of sound ((EAR))

skin account for what % of body weight

10-15%-largest organ

continued...

4. Fat storage: bones also contain yellow bone marrow; made up of fat cells (adipocytes); store triglycerides; fatty acids from breakdown of triglycerides can be used as fuel by cells notes Yellow bone marrow found in bone cavity (medullary ) cavities which store fat Cavity insdie bone is what houses yellow bone marrow^^^^^^^^^^^-- and fat can be used as energy by the body Red bone marrow is where blood cells get formed very important on the EXAM***

continued functions

5.Movement bones serve as sites for attachment of most skeletal muscles; when muscles contract, they pull on bones; generates movement at joint 6. Support: -skeleton supports weight of body -provides its structural framework

bone structure can be organized into ___ classes

5; all bones fit into categorizes based on shapes

Appositional growth (continued):

As new lamellae are added, older deeper circumferential lamellae are removed or restructured into osteons Bone growth in width may continue after bone growth in length ceases; depends on factors such as hormones, forces to which bone is subjected, and diet

Endochondral ossification:

Bone development for all bones below head except clavicles Begins in fetal stage of development for most bones; some bones (wrist and ankle) ossify much later Many bones complete ossification by age 7

Ossification or osteogenesis (continued):

Bones formed by intramembranous ossification are built on model (starting material) made of membrane of embryonic connective tissue Bones formed by endochondral ossification are built on model of hyaline cartilage intramembranous- immature connective tissue to bone endrochondral- hyaline cartilage to bone

Once cartilage model forms, endochondral ossification occurs in following steps:

Chondroblasts in blood vessel-filled perichondrium differentiate first into osteogenic cells, then osteoblasts, forming periosteum Bone begins to form where osteoblasts have built bone collar on external surface of bone At same time internal cartilage begins to calcify and chondrocytes die as connection to blood supply is severed; leaves calcified cartilage and tiny cavities

Process of longitudinal growth (continued):

Chondrocytes that reach zone of calcification die (far from blood supply) and matrix calcifies Calcified cartilage is replaced with bone in zone of ossification ---Osteoblasts invade calcified cartilage and lay down bone on top ---Eventually calcified cartilage and primary bone are resorbed by osteoclasts and completely replaced with mature bone

Overall compact bone structure (continued):

Circumferential lamellae - outer and inner layers of lamellae just inside periosteum; at boundary with spongy bone; add strength Perforating canals (Volkmann's canals) originate from blood vessels in periosteum; travel at right angles (perpendicular) to central canals of neighboring osteons;connect them to one another

functions of connective tissue

Connective tissue functions: o Connecting and binding - anchor tissue layers in organs and link organs together o Support - bone and cartilage support weight of body o Protection - bone tissue protects internal organs; cartilage and fat provide shock absorption; components of immune system are throughout connective tissues o Transport - blood is fluid connective tissue; main transport medium in body

Covering and lining epithelia and what is simple epithelia?

Covering and lining epithelia - on inner and outer body surfaces; each cell shape may be in varying thicknesses in broad, flat sheets; termed membranes when basement membrane is included: Simple epithelia - one cell-layer thick; adapted for transportation of substances between different tissues -Some have microvilli for increased surface area; some have cilia (move substances through hollow organs); Structure-Function Core Principle

all tissues share two basic components:

Discrete population of cells; related in structure and function Extracellular matrix (ECM) - surrounding material

Osteon structure:

Each osteon contains 4 to 20 lamellae arranged in layered ring structures (concentric lamellae) Lamellar arrangement is very stress resistant Collagen fibers of neighboring lamellae run in opposite directions; resist twisting and bending forces from variety of directions Central canal - endosteum-lined hole in center of each osteon; blood vessels and nerves supply bone Osteocytes in lacunae - small cavities between lamellae; filled with extracellular fluid Neighboring lacunae are connected by network of small passageways (canals) in matrix called canaliculi; cytoplasmic extensions of osteocytes extend through networks; neighboring cells share resources and communicate with one another

Intramembranous ossification (continued):

Early spongy bone is formed as osteoblasts continue to lay down new bone (form trabeculae); smaller trabeculae merge forming larger structures Some mesenchymal cells differentiate and form periosteum; some of vascular tissue in early spongy bone will become bone marrow Spongy bone deep to periosteum becomes heavily calcified; structure is rearranged to form immature compact bone

epithelial tissues

Epithelial tissues - on every internal and external body surface; -barrier between body and external environment; -line organs and fluid-filled cavities;

epithelial tissues are vascular? T/F

False; avascular they get oxygen and nutrients by diffusion from deeper tissues

Endochondral ossification occurs from within model of hyaline cartilage; serves as scaffold for developing bone:

Hyaline cartilage model - chondrocytes, collagen, and ECM all surrounded by connective tissue membrane (perichondrium) and immature cartilage cells (chondroblasts) Begins at primary ossification center; primary bone is first synthesized; replaced with secondary bone Long bones have secondary ossification centers in epiphyses; ossify by similar pattern

hair continued Strand of hair has three visible regions in transverse section:

Inner medulla - soft core only found in thick hair (head); composed of soft keratin Middle cortex - highly structured and organized with several layers of keratinocytes containing hard keratin; provides strength Outermost cuticle -single layer of overlapping keratinocytescontaining hard keratin; provides mechanical strength

Intramembranous ossification (continued):

Larger bones have more than one primary ossification center Leads to pieces of bone that must fuse to one another over time Example of early incomplete ossification is fontanels (soft spots) in skulls of newborn babies

Shapes of bones

Long bones- named for overall shape; not actual size (some are quite small); longer than they are wide; include most bones in arms and legs Short bones also named for shape rather than size; roughly cube-shaped or about as long as they are wide; include bones of wrist or carpals and ankle or tarsals Flat bones thin and broad bones; include ribs, pelvis, sternum (breastbone), and most skull bones Irregular bones include vertebrae and certain skull bones; do not fit into other classes because of irregular shapes Sesamoid bones specialized bones located within tendons; usually small, flat, and oval-shaped; give tendons mechanical advantage; give muscles better leverage; patella (kneecap) is example

what are 4 basic types of connective tissue proper

Loose connective tissue Dense connective tissue Reticular tissue Adipose tissue

Events of intramembranous ossification:

Mesenchymal cells differentiate into osteogenic cells, then osteoblasts, at primary ossification site Osteoblasts secrete organic matrix; calcium salts and other inorganic matrix components are deposited in trabeculae over few days (calcification) --Hardens primary bone --Osteoblasts trapped in lacunae become osteocytes

Longitudinal growth continues at epiphyseal plate as long as mitosis continues in zone of proliferation:

Mitotic rate slows around ages of 12-15 years while ossification continues; epiphyseal plates shrink as zone of proliferation is overtaken by zone of calcification and ossification Between ages of 1821, zone of proliferation is completely ossified; longitudinal growth stops; epiphyseal plate is closed Epiphyseal line is calcified remnant of epiphyseal plate

nails and nail plate

Nails hard accessory structures at ends of digits composed of stratified squamous epithelium filled with hard keratin Nail plate most visible component of nail on top of underlying epidermal nail bed divided into: --Nail body - visible portion of nail plate --Nail root - portion of plate under skin --Location of nail matrix containing actively dividing cells

Neurons

Neurons - excitable (like muscle cells); once mature, no longer divide by mitosis; three main components - Cell body (soma) - biosynthetic center of neuron; location of nucleus and most organelles - Solitary axon extends from one end of soma; responsible for moving nerve impulse from soma to target cell (another neuron, muscle cell, or gland); Cell-Cell Communication Core Principle - Dendrites - other extensions protruding from soma; typically short with multiple branches; receive impulses from axons of neighboring neurons; deliver impulses to soma

epithelial tissue is classified by two criteria

Number of cell layers and shape of cells in those layers; both have functional significance Simple epithelia -single cell layer Stratified epithelia- more than one cell layer Squamous- flattened Cuboidal cells- short Columnar cells- tall and elongated

Bone is a dynamic tissue; continually changing as older bone is broken down for raw materials to build new bone; three types of bone cells are responsible for bone's dynamic nature:

Osteoblasts Osteocytes Osteoclasts

Osteocytes

Osteoblasts eventually surround themselves with matrix in small cavities (lacunae); become osteocytes that no longer actively synthesize bone matrix Osteocytes (continued) No longer metabolically active except for maintaining bone extracellular matrix Appear to have ability to recruit osteoblasts to build up or reinforce bone under tension

Bones grow not only in length but also in width (appositional growth)

Osteoblasts, in between periosteum and bone surface, lay down new bone Appositional growth does not result in immediate formation of osteons; instead, new circumferential lamellae are formed

Endochondral ossification steps (continued):

Osteoclasts etch opening in bone collar for blood vessel and bone cell entry into primary ossification center Osteoblasts replace calcified cartilage with early spongy bone; others continue enlarging bone collar Cavities enlarge and combine; medullary cavity develops Secondary ossification centers develop in epiphyses

transport across simple epithelia occurs via 2 routes:

Paracellular transportation o substances leak BETWEEN cells in epithelial membrane o limited due to tight junctions that make spaces between cells nearly impermeable Transcellular transportation o substance enters cell by crossing plasma membrane o diffuses across cytosol o exits cell through plasma membrane at opposite side

Structure of a long bone Periosteum and Perforating fibers (Sharpey's fibers)

Periosteum-membrane composed of dense irregular collagenous connective tissue; rich with blood vessels and nerves surrounds outer surface of long bones Perforating fibers (Sharpey's fibers) made of collagen; anchors periosteum firmly to underlying bone surface by penetrating deep into bone matrix

Intramembranous ossification - forms many flat bones, (skull and clavicles) during fetal development:

Primary bone - formed within mesenchymal membrane composed of embryonic connective tissue; richly supplied with blood; populated with mesenchymal cells Recall flat bone structure is two outer layers of compact bone with inner (middle) layer of spongy bone Middle layer of spongy bone ossifies before outer compact bone layers; begins from primary ossification center

Process of bone formation is

Process of bone formation is ossification or osteogenesis; begins in embryonic period; continues through childhood with most bones completing process by age 7: Can proceed by two different mechanisms; both have similar features: --First bone formed is immature primary (woven) bone; irregularly arranged collagen bundles, osteocytes, and sparse inorganic matrix --Usually primary bone is broken down by osteoclasts and replaced with mature secondary or lamellar bone; more inorganic matrix and increased strength

Integumentary system functions - critical for protecting underlying organs or maintaining homeostasis:

Protection - from mechanical trauma, pathogens, and environment: -Stratified squamous, keratinized epithelium provides durable but flexible surface; protects body from mechanical trauma (stretching, pressure, or abrasions) -Provides continuous barrier to invasion by microorganisms or pathogens -Contains cells of immune system that destroy pathogens before they invade deeper tissues -Glands secrete antimicrobial substances; sebaceous gland secretions give surface of skin slightly acidic pH (acid mantle); inhibits growth of many pathogens -Provides protection from environmental hazards, including absorption of ultraviolet light (UV), before deeper tissues are damaged -Secretes hydrophobic lipid-based chemicals; repel ionic (salt) and polar covalent (water) molecules; keeps them from both leaving and entering body via skin; critical for maintaining water and electrolyte homeostasis in wide range of weather conditions (main function is protection)

Thermoregulation:

Relies on negative feedback loops for maintenance of stable internal temperature Example of Feedback Loops Core Principle Internal body temperature is determined mostly by -Muscle activity -Chemical reactions (metabolism

Endochondral ossification steps (continued):

Remaining ossified cartilage replaced by bone Medullary cavity enlarged by osteoclasts; fills with bone marrow Epiphyses finish ossifying -Cartilage only remains in epiphyseal plates and on articular surfaces where bones interact at joint (articular cartilage) Articular cartilage persists into adulthood; epiphyseal plates are eventually replaced with bone, once growth in length ceases

Remaining 2/3 blood supply of long bones comes from___

Remaining two-thirds supplied by one or two nutrient arteries; enter bone through small hole in diaphysis (nutrient foramen) Nutrient arteries bypass compact bone to supply internal structures of bone Epiphyses receive some blood supply from nutrient arteries; majority comes from small blood vessels that enter and exit through small holes in compact bone

Osteoclasts

Responsible for bone resorption; cell secretes hydrogen ions and enzymes; break down bone matrix Completely different overall cell structure than other two cell types; large multinucleated cells; resemble jellyfish; derived from fusion of cells from bone marrow Eventually located in shallow depressions on internal and external surfaces of bone Hydrogen ions dissolve components of inorganic matrix; enzymes break down organic matrix Liberated substances from breakdown of bone include nutrients, minerals, amino acids, and sugars; absorbed by various transport methods into osteoclast cytosol Substances can be released into blood; might be reused or excreted from body as waste products

Reticular layer

Reticular layer -deep thicker layer -separates dermis from hypodermis -mostly dense irregular connective tissue -largely irregularly arranged collagen bundles: --Collagen bundles strengthen dermis --prevent traumatic injuries from damaging deeper tissues -Elastic fibers allow dermis to return to its original shape and size after stretching -Rich in proteoglycans that draw water into ground substance; keeps skin firm and hydrated -Lamellated (Pacinian) corpuscles - sensory receptors embedded within reticular layer; respond mainly to changes in pressure and vibration -Blood vessels, sweat glands, hairs, sebaceous glands, and adipose tissue are also present

Simple trick to remember strata of epidermis:

Simple trick to remember strata of epidermis: "Brilliant Studying Gives Loads of Confidence" Think of "B" in "basale" as standing for "bottom"; it is bottom layer

Skeletal system includes:

Skeletal system includes: Bones, joints, and associated supporting tissues Bones - main organs of system: Like any organ, composed of more than osseous tissue Also dense regular, irregular collagenous connective tissue and bone marrow

Structure of spongy bone:

Spongy bone - usually not weight-bearing like compact bone; much less densely packed Network of struts reinforces compact bone; resists forces from variety of directions Provides protective structure for bone marrow tissue

layers continued

Stratum lucidum o narrow layer of clear, dead keratinocytes o only in thick skin Stratum corneum o outermost layer o several layers of dead, flattened keratinocytes with thickened plasma membranes o Filled with keratin bundles (little else) o Sloughed off or exfoliated mechanically as desmosomes holding cells together are lost

Understanding Epidermal Growth

Suppose for simplicity's sake that skin has one row of cells in each epidermal stratum: Cell A undergoes mitosis, and one of two daughter cells (cell B in diagram) is now in stratum spinosum Other daughter cell of cell A divides again, producing two more daughter cells, one of which pushes cell B into stratum granulosum Cell B is now quite far from blood supply and becomes coated with lipid-based substance, causing the cell to die Stem cells continue to divide, pushing cell B even farther away from blood supply, into stratum lucidum and then into stratum corneum Cell B is now dead cell filled with keratin; will eventually be sloughed off skin surface

ECM is found beneath cells in

THIN basement membrane make up of two components 1. Basal lamina- ECM synthesized by epithelial cells; consist of collagen fibers and ground substance 2. Reticular lamina -synthesized by underlying connective tissue; consists of reticular fibers and ground substance Together they glue epithelial tissue to underlying connective tissue; anchor underlying blood vessels in place; provide barrier bn epithelia and underlying tissues

thick skin thin skin callus

Thick skin -about as thick as paper towel; -all five epidermal layers and very thick stratum corneum; -no hair follicles; many sweat glands Thin skin -covers areas of body not subjected to as much mechanical stress -about as thick as sheet of printer paper -only four layers (no stratum lucidum) -Each layer is thinner than those of thick skin -Numerous hairs, sweat glands, and sebaceous glands present Callus -additional layers of stratum corneum -forms in either thick or thin skin in response to repetitive pressure

Three types of muscle tissue

Three types of muscle tissue feature different structural and functional characteristics: -Skeletal muscle -Cardiac muscle -Smooth muscle Skeletal and cardiac muscle tissues are striated; smooth muscle tissue is not

Structure of spongy bone (continued):

Trabeculae - struts or ribs of bone; covered with endosteum ---Usually not arranged into osteons ---Composed of concentric lamellae with osteocytes in lacunae; communicate through canaliculi No central or perforating canals supplying blood to trabeculae; obtain blood from vessels in bone marrow

Types of adipose tissue

White adipose tissue --predominant fat tissue; --appears white; --adipocytes with one large lipid inclusion in cytosol; --deep to skin as subcutaneous fat, and in abdomen, breasts, hips, buttocks, and thighs; --visceral fat surrounds heart and abdominal organs Brown adipose tissue -less common; -has brown appearance due to numerous mitochondria in cytoplasm and vast blood supply; -contains multiple lipid inclusions; -more readily converted to energy to produce heat in cold temperatures

Epiphyseal plate zones (continued):

Zone of hypertrophy and maturation (next region closer to diaphysis) - mature chondrocytes Zone of calcification (second to last region) - dead chondrocytes; some calcified Zone of ossification (last region) - calcified chondrocytes and osteoblasts

Cell juctions

another way cells bind to one another; neighboring cell's plasma membrane are linked by??? (answer- integral proteins) 3 types of cell junctions?? answer -tight junctions -desmosomes -gap junctions

Blood and nerve supply to bone

bones are well supplied with blood vessels and sensory nerve fibers: Blood supply to short, flat, irregular, and sesamoid bones is provided mostly by ___? Answer: vessels in periosteum that penetrate bone Long bones get third of their blood supply from?? Answer: periosteum; mostly supplies compact bone --

Epiphyseal plate -

composed of hyaline cartilage that did not ossify; five different zones of cells: Zone of reserve cartilage - (closest to epiphysis) cells that are not directly involved in bone growth but can be recruited for cell division if needed Zone of proliferation (next region) - actively dividing chondrocytes in lacunae

connective tissue are divided into 2 basic groups:

connective tissue proper and specialized connective tissue

Histology of hard outermost compact bone and porous inner spongy bone tissue are quite

different Both gross and histological differences can be attributed to different functions of each region; Structure-Function Core Principle

Structure of short, flat, irregular, and sesamoid bones: do not have ___? Covered by___? Internal structure Some flat and irregular bones of skull contain___?

do NOT have diaphyses, epiphyses, medullary cavities, epiphyseal lines, or epiphyseal plates Covered by periosteum, with associated perforating fibers, blood vessels, and nerves Internal structure - two outer layers of thin compact bone with middle layer of spongy bone (diploë) and associated bone marrow Some flat and irregular bones of skull contain hollow, air-filled spaces (sinuses), which reduce bone weight **Frontal, sphenoid, ethmoid, maxillae 4 bones that have sinuses

true membranes

do not open to outside of body; two examples: Serous membranes or serosae - line pericardial, peritoneal, and pleural body cavities: ---- Consist of mesothelium (thin layer of simple squamous epithelium), associated basement membrane, and layer of connective tissue Fold over themselves; appearance of two layers; outer parietal layer lines body wall; inner visceral layer covers organ within body cavity Mesothelial cells produce thin, watery serous fluid; fills space between parietal and visceral layers; reduces friction created when organs (heart or lungs) move within respective membranes

Excretion

elimination of waste products and toxins from body most occurs at other organs like kidneys skin and accessory structures make small but significant contribution

Protein fibers-

embedded within ground substance -long molecules composed of. multiple fibrous subunits with roselike structure; -enormous tensile strength; resist being pulled apart length wise -three protein fiber types

cutaneous membrane-2 main components

epidermis-superficial layer; keratinized stratified squamous epithelium resting on basement membrane Dermis - deep to epidermis and basement membrane; loose connective tissue and dense irregular connective tissue dermal papillae creates fingerprints

two main components of ECM

ground substance and protein fibers:

Accessory structures or appendages of integument include:

hair, nails, and glands derived from epithelium only assist in overall function of system: Hair (pili) --small filamentous structures --protrude from surface of skin over entire body except in regions with thick skin, lips, and parts of external genitalia Hair is too sparse in humans to play significant role in thermoregulation, as in other mammals: -Provides protection by preventing substances and organisms from entering eyes and nose -Protects underlying skin of scalp from UV radiation and mechanical trauma -Associated with small sensory neuron; plays role in detecting changes in environment

Hair

hair- composed of two main parts: -shaft and -root; -both made of stratified squamous keratinized epithelial cells in various stages of development Shaft -Portion of hair projecting from skin's surface -Made of columns of dead keratinized epithelial cells that have completed keratinization process Root Segment of hair embedded in dermis surrounded by small sensory neuron Indented at base by projection of blood vessels from dermis (hair papilla) Root and hair papilla collectively known as hair bulb Root is embedded in hair follicle; infolding of epidermis (epithelial root sheath) extends deep into dermis or even hypodermis Root sheath has two components: outer component anchors follicle to dermis; inner component is anchored tightly to hair root

Tight junctions (occluding junctions)

hold cells closely together; space between is impermeable to movement of macromolecules -integral proteins of adjacent cell's plasma membranes are LOCKED together; form seal around apical perimeter of cell -seal may not be complete ; allowing for leakage in SOME tissue example; between cells in blood vessels and prevent blood cells from exiting vessels

mast cells

largest resident cell o Immune system cells filled with cytosolic inclusions (granules) of inflammatory mediators (histamine) o Release mediators (degranulate) when stimulated, causing inflammation (protective response that activates immune system)

Mucous membranes (mucosae) -

line all passages opening to outside of body; respiratory passages, mouth, nasal cavity, digestive tract, and male and female reproductive tracts: Layer of epithelium and basement membrane (connective tissue called lamina propria) and occasionally thin layer of smooth muscle Contain glands with goblet cells; produce and secrete mucus; serve several functions, primarily protection ((notes)) MUSCOSEA ASND MUCOUS MEMBRANES ARE USED INTERCHANGEABLLY ON TEST Lamina propria- is basement membrane of mucous membranes Goblet cells make and secrete mucous

demosomes

linking integral proteins; allow for materials in extracellular fluid to pass through space between cells -Increase strength of tissue by holding cells together; mechanical stress is more evenly distributed --Integral "linker" proteins are attached to intermediate filaments of cytoskeleton for structural reinforcement ---In tissues subjected to great deal of mechanical stress (epithelia of skin)

Keratinocyte life cycle

location and functions of epidermis subject it to physical and environmental stress; stratum corneum continuously sheds dead cells; must be replaced to maintain integrity of epidermis: Dead keratinocytes are replaced by mitosis in stratum basale and spinosum where blood supply is available Keratinocytes in deeper strata divide and push cells above them into more superficial layers Keratinocytes begin life in stratum basale or spinosum; pass through each epidermal layer; shed from stratum corneum Migration from deepest strata to stratum corneum takes 40-50 days to complete

long bones lengthen by

longitudinal growth; involves division of chondrocytes (not osteocytes or osteoblasts) in epiphyseal plate Bone growth takes place at epiphysis on side closest to diaphysis

Red bone marrow

loose connective tissue supports islands of blood-forming hematopoietic cells Amount of red marrow decreases with age Red marrow in adult is only in pelvis, proximal femur and humerus, vertebrae, ribs, sternum, clavicles, scapulae, and some bones of skull Children need more red marrow to assist in growth and development

Osteoblasts

metabolically active bone cells in periosteum and endosteum: Osteogenic cells - flattened cells; differentiate into osteoblasts when stimulated by specific chemical signals Osteoblasts - bone-building cells; perform bone deposition Bone deposition -osteoblasts secrete organic matrix materials; assist in formation of inorganic matrix

specialized connective tissues

more specific functions; include three types of tissue: Cartilage - in joints between bones, ear, nose, and segments of respiratory tract Bone tissue (osseous tissue) - supports body; protects vital organs; provides attachments for muscles that allow for movement; stores calcium; and houses bone marrow (produces blood cells and stores fat) Blood - unique connective tissue with liquid ECM (plasma); consists of mostly water, dissolved solutes, and proteins

goblet cells

most common unicellular exocrine gland; -found in digestive and respiratory tracts; secrete mucus which protects underlying epithelium ---notes Trap viruses and bacteria and get It out of body--protection

Ground substance

most of ECM; extracellular fluid (ECF or interstitial fluid) with water, nutrients, ions, and three families of macromolecules: GAGS, proteoglycans, and protein fibers

epidermis

most superficial layer; composed of several cell types -Keratinocytes - make up about 95% of epidermis -structural features make epidermis stronger and less susceptible to mechanical trauma: -Manufacture keratin - tough fibrous protein ----Structure-Function Core Principle -Linked together by desmosomes ---intercellular junctions that hold cells together

glands; skin contains 2 basic types of glands

o both derived from epidermal cells o located deeper in dermis 1. Sweat (sudoriferous) glands - produce sweat 2. Sebaceous glands - produce oily sebum

Adipose tissue

o fat-storing adipocytes and surrounding fibroblasts and ECM; o adipocytes can increase in size to a point where fibroblasts and ECM are scarcely visible; o functions: -Fat storage (major energy reserve of body) -Insulation (retains warmth) -Shock absorption and protection

connective tissue proper

o widely distributed in body o connect tissue and organs to one another o components of internal architecture of some organs

Bone or osseous tissue -

primary tissue found in bone; composed mostly of extracellular matrix with a small population of cells scattered throughout Extracellular matrix of bone is ____? A: unique: Inorganic matrix - minerals make up about 65% of bone's total weight Organic matrix - makes up remaining 35%; consists of collagen fibers and usual ECM components

Cutaneous membrane -

refers to skin; largest organ of body; consists of -Outer layer of keratinized stratified squamous epithelium (epidermis); tough, continuous protective surface; protects structures deep to it -Dermis ---Layer of loose connective tissue beneath epidermis plus deeper layer of dense irregular connective tissue ---Home to many blood vessels; provides means for oxygen and nutrients to diffuse into avascular epidermis notes--The epidermis has to be thin bc it relies on diffusion for oxygen and nutreitnts

Process of longitudinal growth (continued): Each zone of epiphyseal plate, except zone of _____ is actively involved in longitudinal growth

reserve cartilage, : Chondrocytes divide in zone of proliferation; force cells ahead of them into next zones (toward diaphysis) Chondrocytes that reach zone of hypertrophy and maturation enlarge and stop dividing; lacunae are larger

endocrine glands

secrete products, usually hormones, directly into bloodstream WITHOUT use of ducts: --Allow products to have systemic effects (on distant cells) --Example of Cell-Cell Communication Core Principle

Epiphyseal lines

separate both proximal and distal epiphyses from diaphysis; remnant of epiphyseal plates (growth plates); line of hyaline cartilage found in developing bones of children

continued structure of a lone bone -diaphysis -Compact bone -Spongy bone (cancellous bone)

shaft of long bone; each end is epiphysis; covered with thin layer of hyaline cartilage (articular cartilage) found within joints (articulations) between bones Hollow cavity (marrow cavity) within diaphysis contains either red or yellow bone marrow, depending on bone and age of individual. ((**NOTE Yellow bone marrow is in hollow cavity in adult )))------------ -Compact bone one of two bone textures; hard, dense outer region; allows bone to resist linear compression and twisting forces among other stresses -------- -Spongy bone (cancellous bone) second bone texture; inside cortical bone; honeycomb-like framework of bony struts; allows long bones to resist forces from many directions; provides cavity for bone marrow

simple cuboidal epithelium-

single layer of cube-shaped cells with large central nucleus; thin enough for rapid substance diffusion; in segments of renal tubules, respiratory passages, ducts of many glands, and thyroid gland

simple columnar epithelium

single layer of rectangular-shaped cells with nuclei in basal portion of cell; often microvilli (small intestine) or cilia; (uterine tubes and segments of respiratory tract) on apical plasma membrane

skin markings

small visible lines in epidermis created by interaction between dermis and epidermis; best seen in thick skin Dermal ridges - areas where dermal papillae are more prominent due to presence of thick collagen bundles Dermal ridges indent overlying epidermis to create epidermal ridges; enhance gripping ability of hands and feet: ----Occur in characteristic patterns; loops, arches, and whorls; genetically determined and unique to each person ----Sweat pores open along ridges; leave thin film or fingerprint on things touched with fingers

muscle tissue

specialized for contraction; three types share ability to turn chemical energy of ATP into mechanical energy of movement o Walking, breathing, heart beating, and propulsion of substances through hollow organs all result from contractions of different muscle tissues o Main component of muscle tissue is muscle cell (myocyte); excitable (respond to electrical or chemical stimulation)

epidermal strata (layerS)

structurally distinct; deep to superficial: Stratum basale - (stratum germinativum) --single layer of stem cells resting on basement membrane --Closest cells to dermal blood supply --most metabolically and mitotically active strata --Responsible for Vitamin D synthesis and replacement of dead keratinocytes (lost from superficial layers)

gland

structure of epithelial origin; synthesizes and secretes product from designated secretory cells -Arises from epithelial tissue that migrated into deeper connective tissue instead of remaining at surface -Classified either by shape or by how products are released -Products released by two mechanisms: Endocrine Exocrine

Histology

study of normal structures of tissues (group of structurally and functionally related cells and their external environment; together perform common functions)

Structure of compact bone is continuously

subjected to great deal of stress; tends to strain or deform objects like bone; must be able to withstand these forces or suffer damage: Compact bone cross section resembles forest of tightly packed trees; each tree is a unit called osteon or Haversian system Rings of each tree are made up of thin layers of bone called lamellae

endosteum

thin membrane that covers Bony struts of spongy bone and all inner surfaces of bone

epithelial tissues consist of tightly packed cells linked together by

tight junctions and desmosomes which make sheets of cells fairly impermeable and resistant to physical stresses and mechanical injury

Yellow bone marrow

triglycerides, blood vessels, and adipocytes

organ

two or more tissues that combine structurally and functionally: o Simple organ example - skeletal muscle: -Two main tissues - skeletal muscle and dense irregular collagenous connective -Each has distinct functional role; skeletal muscle tissue allows contraction; surrounding connective tissue binds muscle cells together and supports them so that their activity produces contraction of whole organ

simple squamous epithelium

very thin single layer of cells; "fried egg" appearance; adapted for rapid diffusion of substances (oxygen, carbon dioxide, fluids, and ions); in air sacs of lung, specific segments of kidney tubules, and lining blood vessels

skin plays critical role in

vitamin D synthesis: -Modified cholesterol molecule (precursor) converted to cholecalciferol by exposure of epidermis to UV radiation -Cholecalciferol is released into blood -modified first by liver, then by kidneys, forming calcitriol (active form of vitamin D) -required for calcium ion absorption from small intestine -Calcium ion - critical for nerve function, muscle contraction, building and maintaining bone tissue (many other physiological functions)