Chapter 4

Polarity

Cells have polarity (top and bottom)

Histology

Study of tissues

Collagen

-Strongest and most abundant type -Tough; provides high tensile strength

Primary germ layers

-Superficial to deep: ectoderm, mesoderm, and endoderm -Formed early in embryonic development -Specialize to form the four primary tissues ***Nerve tissue arises from ectoderm ***Muscle and connective tissues arise from mesoderm ***Epithelial tissues arise from all three germ layers

Bone (osseous tissue)

-Supports and protects body structures -Stores fat and synthesizes blood cells in cavities -Has more collagen compared to cartilage -Has inorganic calcium salts -Osteoblasts produce matrix -Osteocytes maintain the matrix -Reside in cavities in matrix called lacunae -Osteons: individual structural units ****Richly vascularized

Connective Tissue Cells

"Blast" cells -Immature form of cell that actively secretes ground substance and ECM fibers -Fibroblasts found in connective tissue proper -Chondroblasts found in cartilage -Osteoblasts found in bone -Hematopoietic stem cells in bone marrow "Cyte" cells -Mature, less active form of "blast" cell that now becomes part of and helps maintain health of matrix

Connective tissue

-The most abundant and widely distributed of primary tissues -Major functions: binding and support, protecting, insulating, storing reserve fuel, and transporting substances (blood) -Four main classes: Connective tissue proper Cartilage Bone Blood

Serous Membranes

-Also called serosae -Found in closed ventral body cavities -Constructed from simple squamous epithelium (called mesothelium) resting on thin areolar connective tissue -Parietal serosae line internal body cavity walls -Visceral serosae cover internal organs -Cavity between layers is filled with slippery serous fluid, so these are moist membranes -Special names given to show location: pleurae (lungs), pericardium (heart), peritoneum (abdomen)

Cutaneous Membranes

-Another name for skin -Keratinized stratified squamous epithelium (epidermis) attached to a thick layer of connective tissue (dermis) -Unlike other membranes, skin is a dry membrane

Tissues with virtually no functional regenerative capacity

-Cardiac muscle and nervous tissue of brain and spinal cord -New research shows cell division does occur, and efforts are underway to coax them to regenerate better

Covering and Lining Membranes

-Composed of at least two primary tissue types: an epithelium bound to underlying connective tissue proper layer -Three types: Cutaneous membranes Mucous membranes Serous membranes

Regeneration

-Epithelial cells have high regenerative capacities -Highly mitotic

Specialized contacts

-Epithelial tissues need to fit closely together -Many form continuous sheets -Specialized contact points bind adjacent epithelial cells together Lateral contacts include: Tight junctions Desmosomes

Exocrine

-Externally secreting (example: sweat) -Secretions are released onto body surfaces, such as skin, or into body cavities -More numerous than endocrine glands -Secrete products into ducts -Examples include mucous, sweat, oil, and salivary glands Can be: Unicellular Multicellular

Other cell types in connective tissues

-Fat cells Store nutrients -White blood cells Neutrophils, eosinophils, lymphocytes Tissue response to injury -Mast cells Initiate local inflammatory response against foreign microorganisms they detect -Macrophages Phagocytic cells that "eat" dead cells, microorganisms; function in immune system

3 main elements of connective tissue

-Ground substance -Fibers -Cells ***The first two elements (ground substance and fibers) together make up the extracellular matrix -Composition and arrangement of these three elements vary considerably in different types of connective tissues

Muscle Tissue

-Highly vascularized -Responsible for most types of movement -Muscle cells possess myofilaments made up of actin and myosin proteins that bring about contraction -Three types of muscle tissues: Skeletal muscle Cardiac muscle Smooth muscle

Endocrine

-Internally secreting (example: hormones) -Ductless glands -Secretions are not released into a duct; are released into surrounding interstitial fluid, which is picked up by circulatory system -Secrete (by exocytosis) hormones, messenger chemicals that travel through lymph or blood to their specific target organs -Target organs respond in some characteristic way

Basal surface

-Lower attached side, faces inwards toward body -Attaches to basal lamina, an adhesive sheet that holds basal surface of epithelial cells to underlying cells

Nervous Tissue

-Main component of nervous system (brain, spinal cord, nerves) -Regulates and controls body functions -Made up of two specialized cells: ****Neurons: specialized nerve cells that generate and conduct nerve impulses ****Supporting cells (neuroglial cells or glial cells) that support, insulate, and protect neurons

Cartilage

-Matrix secreted from chondroblasts (during growth) and chondrocytes (adults) -Chondrocytes found in cavities called lacunae -80% water, with packed collagen fibers and sugar proteins (chondroitin and hyaluronic acid) -Tough yet flexible material that lacks nerve fibers

Blood

-Most atypical connective tissue because it is fluid -Consists of cells surrounded by matrix (plasma) -Red blood cells are most common cell type -Also contains white blood cells and platelets -Fibers are soluble proteins that precipitate during blood clotting -Functions in transport and in carrying nutrients, wastes, gases, and other substances

Mucous Membranes

-Mucosa indicates location, not cell composition *Also called mucosae -Line body cavities that are open to the exterior (example: digestive, respiratory, urogenital tracts) -Moist membranes bathed by secretions (or urine) -Epithelial sheet lies over layer of loose connective tissue called lamina propria -May secrete mucus

Multicellular exocrine glands

-Multicellular exocrine glands are composed of a duct and a secretory unit Classified by: Structure Mode of secretion

Avascular, but innervated

-No blood vessels are found in epithelial tissue -Must be nourished by diffusion from underlying connective tissues -Epithelia are supplied by nerve fibers, however

Avascular

-Receives nutrients from membrane surrounding it (perichondrium) -Periochondrium gives rise to chondroblasts and chondrocytes

Reticular

-Short, fine, highly branched collagenous fibers (different chemistry and form from collagen fibers) -Branching forms networks that offer more "give"

Multicellular exocrine glands structure

-Simple exocrine glands have unbranched ducts, but compound glands have branched ducts -In a tubular gland, secretory cells form a duct, whereas in alveolar glands, secretory cells form sacs -Tubuloalveolar glands have both types

Unicellular exocrine glands

-The only important unicellular glands are mucous cells and goblet cells -Found in epithelial linings of intestinal and respiratory tracts -All produce mucin, a sugar-protein that can dissolve in water to form mucus, a slimy protective, lubricating coating

Common Characteristics of Connective Tissue

-Three characteristics make connective tissues different from other primary tissues: -All have common embryonic origin: all arise from mesenchyme tissue as their tissue of origin -Have varying degrees of vascularity (cartilage is avascular, bone is highly vascularized) -Cells are suspended/embedded in extracellular matrix (ECM) (protein-sugar mesh) -Matrix supports cells so they can bear weight, withstand tension, endure abuse

Ground substance

-Unstructured gel-like material that fills space between cells -Medium through which solutes diffuse between blood capillaries and cells

Apical surface

-Upper free side, is exposed to surface or cavity -Most apical surfaces are smooth, but some have specialized fingerlike projections called microvilli

Tissue Repair

-When the body's barriers are compromised, the inflammatory and immune responses are activated -Repair starts very quickly -Repair is the function of the inflammatory process -Repair can occur in two major ways: ***Regeneration: same kind of tissue replaces destroyed tissue, so original function is restored ***Fibrosis: connective tissue replaces destroyed tissue, and original function lost

Epithelial tissue (epithelium)

-a sheet of cells that covers body surfaces or cavities -Two main forms: Covering and lining epithelia -on external and internal surfaces (example: skin) Glandular epithelia -Secretory tissue in glands (example: salivary glands) Main functions: protection, absorption, filtration, excretion, secretion, and sensory reception

Classification of Epithelia

All epithelial tissues have two names ----First name indicates number of cell layers Simple or Stratified -----Second name indicates shape of cells Squamous, Cuboidal or Columnar In stratified epithelia, shape can vary in each layer, so cell is named according to the shape in apical layer

Stratified columnar

Also very limited distribution in body Small amounts found in pharynx, in male urethra, and lining some glandular ducts Usually occurs at transition areas between two other types of epithelia Only apical layer is columnar

Hyaline Cartilage

Description: Amorphous but firm matrix; collagen fibers form an imperceptible network; chondroblasts produce the matrix and when mature (chondrocytes) lie in lacunae Function: Supports and reinforces; serves as resilient cushion; resists compressive stress. Location: Forms most of the embryonic skeleton; covers the ends of long bones in joint cavities; forms costal cartilages of the ribs; cartilages of the nose, trachea, and larynx.

Cardiac Muscle Tissue

Description: Branching, striated, generally uninucleate cells that interdigitate at specialized junctions (intercalated discs). Function: As it contracts, it propels blood into the circulation; involuntary control. Location: The walls of the heart.

Elastic Tissue

Description: Dense regular connective tissue containing a high proportion of elastic fibers Function: Allows tissue to recoil after stretching; maintains pulsatile flow of blood through arteries; aids passive recoil of lungs following inspiration. Location: Walls of large arteries; within certain ligaments associated with the vertebral column; within the walls of the bronchial tubes. DENSE CONNECTIVE TISSUE PROPER

Areolar tissue

Description: Gel-like matrix with all three fiber types; cells: fibroblasts, macrophages, mast cells, and some white blood cells. Function: Wraps and cushions organs; its macrophages phagocytize bacteria; plays important role in inflammation; holds and conveys tissue fluid Location: Widely distributed under epithelia of body, e.g., forms lamina propria of mucous membranes; packages organs; surrounds capillaries. LOOSE CONNECTIVE TISSUE PROPER

Osseous Tissue

Description: Hard, calcified matrix containing many collagen fibers; osteocytes lie in lacunae. Very well vascularized. Function: Supports and protects (by enclosing); provides levers for the muscles to act on; stores calcium and other minerals and fat; marrow inside bones is the site for blood cell formation (hematopoiesis). Location: bones

Skeletal Muscle Tissue

Description: Long, cylindrical, multinucleate cells; obvious striations. Function: Voluntary movement; locomotion; manipulation of the environment; facial expression; voluntary control. Location: In skeletal muscles attached to bones or occasionally to skin.

Reticular Tissue

Description: Loose network of reticular fibers in a gel-like ground substance; reticular cells lie on the network. Function: Fibers form a soft internal skeleton (stroma) that supports other cell types including white blood cells, mast cells, and macrophages. Location: Lymphoid organs (lymph nodes, bone marrow, and spleen). LOOSE CONNECTIVE TISSUE PROPER

Adipose Tissue

Description: Matrix as in areolar, but very sparse; closely packed adipocytes, or fat cells, have nucleus pushed to the side by large fat droplet. Function: Provides reserve food fuel; insulates against heat loss; supports and protects organs. Location: Under skin in subcutaneous tissue; around kidneys and eyeballs; within abdomen; in breasts. LOOSE CONNECTIVE TISSUE PROPER

Fibrocartilage

Description: Matrix similar to but less firm than that in hyaline cartilage; thick collagen fibers predominate. Function: Tensile strength allows it to absorb compressive shock. Location: Intervertebral discs; pubic symphysis; discs of knee joint.

Nervous Tissue Diagram

Description: Neurons are branching cells; cell processes that may be quite long extend from the nucleus-containing cell body; also contributing to nervous tissue are nonexcitable supporting cells. Function: Neurons transmit electrical signals from sensory receptors and to effectors (muscles and glands); supporting cells support and protect neurons. Location: Brain, spinal cord, and nerves.

Dense Irregular Tissue

Description: Primarily irregularly arranged collagen fibers; some elastic fibers; fibroblast is the major cell type Function: Withstands tension exerted in many directions; provides structural strength. Location: Fibrous capsules of organs and of joints; dermis of the skin; submucosa of digestive tract. DENSE CONNECTIVE TISSUE PROPER

Dense Regular Tissue

Description: Primarily parallel collagen fibers; a few elastic fibers; major cell type is the fibroblast. Function: Attaches muscles to bones or to muscles; attaches bones to bones; withstands great tensile stress when pulling force is applied in one direction. Location: Tendons, most ligaments, aponeuroses. DENSE CONNECTIVE TISSUE PROPER

Blood Tissue

Description: Red and white blood cells in a fluid matrix (plasma). Function: Transport respiratory gases, nutrients, wastes, and other substances Location: Contained within blood vessels.

Transitional epithelium

Description: Resembles both stratified squamous and stratified cuboidal; basal cells cuboidal or columnar; surface cells dome shaped or squamouslike, depending on degree of organ stretch. Function: Stretches readily, permits stored urine to distend urinary organ. Location: Lines the ureters, bladder, and part of the urethra. EMPTY BLADDER=Cuboidal FULL BLADDER= Squamous

Elastic Cartilage

Description: Similar to hyaline cartilage, but more elastic fibers in matrix. Function: Maintains the shape of a structure while allowing great flexibility. Location: Supports the external ear (pinna); epiglottis

Simple cuboidal

Description: Single layer of cubelike cells with large, spherical central nuclei. Function: Secretion and absorption. Location: Kidney tubules; ducts and secretory portions of small glands; ovary surface.

Simple squamous

Description: Single layer of flattened cells with disc-shaped central nuclei and sparse cytoplasm; the simplest of the epithelia. Function: Allows materials to pass by diffusion and filtration in sites where protection is not important; secretes lubricating substances in serosae. Location: Kidney glomeruli; air sacs of lungs; lining of heart, blood vessels, and lymphatic vessels; lining of ventral body cavity (serosae).

Pseudostratified columnar

Description: Single layer of cells of differing heights, some not reaching the free surface; nuclei seen at different levels; may contain mucus-secreting cells and bear cilia. Function: Secrete substances, particularly mucus; propulsion of mucus by ciliary action. Location: Nonciliated type in males' sperm-carrying ducts and ducts of large glands; ciliated variety lines the trachea, most of the upper respiratory tract ONLY PSEUDOSTRATIFIED COLUMNAR HAS CILIA; NOT SIMPLE COLUMNAR

Simple columnar

Description: Single layer of tall cells with round to oval nuclei; many cells bear microvilli, some bear cilia; layer may contain mucus-secreting unicellular glands (goblet cells). Function: Absorption; secretion of mucus, enzymes, and other substances; ciliated type propels mucus (or reproductive cells) by ciliary action. Location: Nonciliated type lines most of the digestive tract (stomach to rectum), gallbladder, and excretory ducts of some glands; ciliated variety lines small bronchi, uterine tubes, and some regions of the uterus.

Smooth Muscle Tissue

Description: Spindle-shaped (elongated) cells with central nuclei; no striations; cells arranged closely to form sheets. Function: Propels substances or objects (foodstuffs, urine, a baby) along internal passageways; involuntary control. Location: Mostly in the walls of hollow organs.

Stratified squamous

Description: Thick membrane composed of several cell layers; basal cells are cuboidal or columnar and metabolically active; surface cells are flattened (squamous); in the keratinized type, the surface cells are full of keratin and dead; basal cells are active in mitosis and produce the cells of the more superficial layers. Function: Protects underlying tissues in areas subjected to abrasion. Location: Nonkeratinized type forms the moist linings of the esophagus, mouth, and vagina; keratinized variety forms the epidermis of the skin, a dry membrane. SKIN

Tissues that regenerate extremely well include

Epithelial tissues, bone, areolar connective tissue, dense irregular connective tissue, blood-forming tissue

Tissues

Groups of cells similar in structure that perform common or related function

Three types of cartilage

Hyaline cartilage Elastic cartilage Fibrocartilage

Stratified epithelial tissues

Involve two or more layers of cells New cells regenerate from below Basal cells divide and migrate toward surface More durable than simple epithelia because protection is the major role Types: Stratified squamous epithelium Stratified cuboidal epithelium Stratified columnar epithelium Transitional epithelium

Simple epithelia

Involved in absorption, secretion, or filtration processes Types: Simple squamous epithelium Simple cuboidal epithelium Simple columnar epithelium Pseudostratified columnar epithelium

Multicellular exocrine glands mode of secretion

Merocrine, Holocrine, Apocrine

Mucous Membrane picture

Mucous membranes line body cavities that are open to the exterior.

Elastic fibers

Networks of long, thin, elastin fibers that allow for stretch and recoil

Gland

One or more cells that makes and secretes an aqueous fluid called a secretion Relative number of cells forming the gland Unicellular (example: goblet cells) or multicellular (example: salivary)

Epithelial tissue has five distinguishing characteristics

Polarity Specialized contacts Supported by connective tissues Avascular, but innervated Regeneration

Stratified cuboidal

Quite rare Found in some sweat and mammary glands Typically only two cell layers thick

Connective tissue support

Reticular lamina ----Deep to basal lamina ----Consists of network of collagen fibers Basement membrane -----Made up of basal and reticular lamina -----Reinforces epithelial sheet -----Resists stretching and tearing -----Defines epithelial boundary

Inflammation sets the stage (for repair)

Review powerpoint slide (slide 69 lol) for diagram because I couldn't make it look good on here

Serous membrane picture

Serous membranes line body cavities that are closed to the exterior.

Tissue with moderate regenerating capacity

Smooth muscle and dense regular connective tissue

Connective tissue fibers

Three types of fibers provide support Collagen Elastic fibers Reticular

Aprocrine

accumulate products within, but ONLY apex ruptures; whether this type exists in humans is controversial (maybe mammary cells?)

Holocrine

accumulate products within, then rupture (sebaceous oil glands) (HOLE cell ruptures)

Four basic tissue types

epithelial, connective, muscle, and nervous tissue

Merocrine

most secrete products by exocytosis as secretions are produced (sweat, pancreas)