Chapter 4 - Histology: Part 2

membrane-like structures

mucous and cutaneous membranes

smooth muscle cells

muscle cells that have myofilaments that are arranged as irregular bundles scattered randomly in the cytoplasm

Striated muscle cells

muscle cells that have striations (alternating light and dark bands) caused by the arrangement of the myofilaments that overlap in some areas and not in others

neurons

nerve generate, conduct and receive information in the form of electrical signals; mostly amitotic (do not undergo mitosis)

tissue repair

process of wound healing

neuroglial cells

provide physical support, insulation, and nutrients for neurons, including anchoring neurons and blood vessels in place, monitoring the composition of the ECF, increasing the rate of nerve impulse transmission and circulating the fluid surrounding the brain and spinal cord; mitotic

fibrosis

replacement of damaged or dead cells with fibroblasts that divide by mitosis and and produce collagen to fill in the defect left by injury; the tissue does not regain its ability to function fully

True membranes

serous and synovial membranes: do not open to the outside of the body

dendrite

short, highly branched extensions from nerve cells that receive messages from the axon and other neurons and bring impulses to the cell body

Bone

solid and strong, not active tissue

cartilage

strong connective tissue that supports the body and is softer and more flexible than bone; absorbs shock and is resistant to tension, compression and shearing forces

Obesity

the condition of excess adipose tissue in proportion to lean body mass

nerve impulses

the electrical signals carried by a nerve cell

axon

the extension of a neuron, ending in branching terminal fibers, through which messages pass to other neurons or to muscles or glands

Mast cells

the largest of the cell types in connective tissue proper; immune system cells that have cytosolic inclusions (granules) containing inflammatory mediators.

Fibroblasts

the most abundant cell type in connective tissue that produces protein fibers, ground substance and other elements of ECM; a mature cell with the properties of an immature cell; active cells lie close to collagen as they continually produce collagen proteins

regeneration

the process by which damaged or dead cells are replaced with cells of the same type

nervous tissue

tissue that composes the brain, spinal cord and nerves and carries electrical messages back and forth between the brain and every other part of the body. Composition: neurons, neuroglial cells, ECM mostly made of ground substance with unique proteoglycans and very few protein fibers

synovial membranes

two, connective layers of tissue that line the cavities surrounding freely moving joints. the inner layer consists of synoviocytes (modified fibroblasts) and the external layer is generally a mixture of loose and dense irregular connective tissue

scar tissue

type of dense irregular connective tissue that results from fibrosis

smooth muscle tissue

type of involuntary muscle tissue made up of smooth muscle cells that are flattened with a single, central ovoid nucleus; most are linked by gap junctions in their plasma membrane; found in the wall of nearly every hollow organ, as well as the walls of blood vessels, the eyes, the skin and the ducts of certain glands

Other immune cells

various other immune system cells migrate in and out of different connective tissues, depending on the needs of the body at the time

Leukocytes

white blood cells which function in immunity

Most connective tissues heal by regeneration

Typically done by division of immature cells, except cartilage which has a limited capacity to divide so often heals by fibrosis

Excitable cells

cells that respond to electrical or chemical stimulation

platelets

cellular fragments that play a role in the blood clotting process

erthrocytes

red blood cells that bind and transport oxygen throughout the body

types of muscle tissue

skeletal, cardiac, smooth

Skeletal muscle tissue

type of voluntary muscle tissue found mostly attached to the skeleton Characteristics: long, thin, striated muscle cells (fibers) that are arranged parallel to one another Function: contract to move the body

Epithelial tissues typically undergo regeneration

undergo a great degree of stress, so they regenerate; Skin and digestive tract (stem cells) Live and blood vessels (mature cells)

composition of cartilage

-the ECM, which contains glycosaminoglycans, proteoglycans, collagen fibers and elastic fibers, is largely responsible for its properties -two major cell types: chondroblasts (immature cartilage) and -avascular (unusual among CT types)

Big Picture of Tissues in Organs

Complex Organs: Trachea 1. Dense irregular connective issue (outermost layer) 2. Smooth muscle 3. Hyaline cartilage 4. Loose connective tissue 5. Pseudostratified ciliated columna epithelium (inner rings) Simple Structure: Skeletal muscle 1. Skeletal muscle tissue 2. Dense irregular collagenous connective tissue

Elastic cartilage

Components: -chondrocytes, elastic fibers, ECM Function: -involved in producing and detecting sound (vibration of elastic fibers) Location: -ears -epiglottis of larynx

Dense regular elastic connective tissue

Composition: - parallel elastic fibers with randomly oriented collagen fibers, ground substance Function: -allows tissues to stretch and recoil Location: -large blood vessels -certain ligaments

Adipose connective tissue

Composition: -adipocytes, protein fibers Function: -warm, insulation -shock absorption, protection -major energy reserve in the body Location: -deep to the skin (subcutaneous) in characteristic areas (abdomen, breasts, buttocks, thighs) -surrounds the heart and other organs

Dense regular collagenous connective tissue

Composition: -fibroblasts, collagen fibers (arranged parallel to one another to form bundles), ground substance Function: -strength -resistance to stress in one plane Location: -tendons, ligaments

Dense irregular connective tissue

Composition: -fibroblasts, collagen fibers(primary type), ground substance Function: -strength -resistance to stress in all three planes Location: -deepest layer of skin -around joints, organs

Reticular connective tissue

Composition: -reticular fibers (produced by surrounding fibroblasts), leukocytes Function: -forms internal structure of many organs; web-like net of reticular fibers traps old and foreign cells and house white blood cells -supports smaller vessels and nerves Location: -lymph nodes, spleen, bone marrow, liver -basement membrane -around vessels and nerves

Perichondrium

Dense irregular connective tissue membrane covering cartilage that contains the blood supply for the cartilage; oxygen and nutrients must diffuse from the blood vessels through the ECM to reach the chondrocytes and chondroblasts

plasma

ECM of blood consisting of water, dissolved solutes and proteins (lacks protein fibers)

endomysium (external lamina)

ECM surrounding muscle cells that helps hold muscle cells in the tissue and blends with connective tissue around the muscle cells

Cells of connective tissue proper

Fibroblasts Adipocytes Mast cells Phagocytes Other immune cells

Types of connective tissue proper

Loose connective tissue Dense connective tissue Reticular tissue Adipose tissue

Myofilaments

The contractile proteins, actin and myosin, of muscle cells

intercalcated discs

The division between neighboring cardiac muscle cells. Intercalcated discs include gap junctions and modified tight junctions, which allow the cells to function as a unit and enable communication.

Connective tissues

a diverse group of tissues with a variety of functions: -connecting and binding (in and between organs) -support (bone and cartilage) -protection (bone and cartilage, immune system) -transport (blood)

mucous membrane (mucosa)

a membrane lining all body passages that open to the outside of the body, composed of a layer of epithelium, its basement membrane, lamina propria (a layer of loose connective tissue), and occasionally a thin layer of smooth muscle. Mucosae contain goblet cells that secrete mucus

serosae (serous membranes)

a single, thin sheet of tissue folded over on itself that consists of mesothelium (a layer of simple squamous epithelium), its basement membrane and a layer of loose connective tissue

serous fluid

a thin, watery fluid produced by mesothelial cells which fills the space between the parietal and visceral layers and provides lubrication so that organs can move without friction

cardiac muscle tissue

a type of involuntary, specialized muscle tissue found only in the heart Characteristics: short, thick, striated muscle cells that form branches and are often uninucleate cells are separated by intercalcated discs

synovial fluid

a watery, slippery fluid secrete by synoviocytes that lubricate joints

membrane function

anchor organs in place, serve as barriers, function in immunity, and secrete various substances

Osteoblasts

bone building cells that carry out the process of bone deposition; synthesize ECM, which they secrete by exocytosis, and produce the chemicals required for calcium salts to deposit within ECM Location: -outer surface of bone, close to periosteum (dense irregular collagenous connective tissue)

Specialized connective tissue

cartilage, bone (osseous), blood

Neurons generally do not regenerate

cells are unable to undergo mitosis; damaged neurons are usually replaced by neuroglial cells that divide to produce a scar; however, axons (outside brain and spinal cord) have the ability to regenerate depending on the location and nature of the damage

Skeletal and cardiac muscle tissues generally heal by fibrosis

cells cannot undergo mitosis, so typically heal by fibrosis although skeletal muscle tissue has satellite cells which allows a limited degree of regeneration

Smooth muscle tissue usually regenerates

cells largely retain ability to undergo mitosis so heal by regeneration

inflammatory mediators

chemicals substances that once triggered are released triggering inflammation which activates a response from the immune system

Loose (areolar) connective tissue

composed primarily of ground substance with all three types of protein fibers, fibroblasts and other cells such as adipocytes Function: -support -protection -houses blood vessels supplying epithelium Location: -Deep to epidermis -Walls of hollow organs -Membranes lining body cavities

Dense (fibrous) connective tissue

composed primarily of protein fibers

classes of connective tissue

connective (general) tissue proper and specialized connective tissues

Bone (osseous) tissue

connective tissue with the matrix hardened by calcium phosphate and other minerals Composition -65% inorganic materials (calcium phosphate) -35% organic materials (collagen fibers, osteoid(ground substance)) Functions: -support -protecting vital organs -storing calcium salts -housing bone marrow (tissue that produces blood cells and stores fat)

Connective tissue proper

connects tissues and organs to one another and forms part of the internal structure of some organs

Fibrocartilage

dominated by bundles of collagen fibers Components: -chondrocytes, fibroblasts, collagen fibers, ECM Function: -support -protection -resists compression Location: -fibrous joints -intervertebral discs

myocytes (muscle cells)

excitables cells with cytoplasm filled with myofilaments

Adipocytes

fat cells; most are dominated by a single large inclusion of lipids and the nucleus and other organelles are squashed to the perimeter and difficult to see in sections

Blood

fluid connective tissue of the circulatory system; consists of blood cells and plasma

Bone remodeling

healthy bone constantly undergoes the processes of bone deposition and bone resorption; both can occur simultaneously in different areas tension => increased osteoblast activity and bone deposition pressure => increased osteoclast activity and bone resorption

stem cells

immature cells that renew themselves and have the potential to develop into mature cells

Phagocytes

immune cells that can ingest foreign substances, microorganisms, and dead and damaged cells; two common types are macrophages (resident or migrant) and neutrophils (migrant)

Hyaline cartilage

large amount of ground substance gives uniform, glassy appearance; fetal skeletons start as mostly hyaline cartilage before becoming bone Components: -chondrocytes, bundles of fine collagen fibers, ECM Function: -support -protection -resists compression Location: -between bones in joints (articular cartilage) -between sternum and ribs -nose -respiratory tract

Soma (cell body)

large, centralized portion of the neuron that is the biosynthetic center, where the nucleus and most other organelles are housed

Osteoclasts

large, multinucleated cells that destroy bones; carry out the process of bone resorption, during which they secrete hydrogen ions and enzymes that catalyze reactions to break down the components of ECM

cutaneous membrane (skin)

largest organ of the body; epidermis (outer layer of keratinized stratified squamous epithelium) and dermis (a layer of loose connective tissue and an even deeper layer of dense irregular connective tissue)

Muscle fibers

long, slender cells that make up muscles, formed by the fusion of embryonic myoblasts retained within mature muscle fibers, causing it to be multinucleate; the nuclei are located near the outer edge of the fiber and aid in function as muscles requires near constant synthesis of enzymes, structural proteins and contractile proteins

Composition of connective tissue

loosely packed cells surrounded by protein fibers, all of which are embedded in ground substance

Osteocytes

mature bone cells found in lacunae; they produce substances required for bone maintenance (exocytosis)

chondrocytes

mature cartilage cells found in lacunae (small cavities in ECM)