A&P Chapter 4

Tissue

group of cells that usually have common origin in embryo and function together to carry out specialized activities.

4 types of tissue

epithelial, connective, muscular, and nervous

Classification of connective tissues

1) Embryonic connective tissues - Mesenchyme - Mucous connective tissue 2) Mature connective tissues - Loose conective tissues a) areolar connective b) adipose c) reticular connective - Dense connective tissues a) dense regular connective b) dense irregular connective c) elastic connective - Cartilage a) hyaline cartilage b) fibrocartilage c) elastic cartilage - Bone tissue - Liquid connective tissue a) blood tissue b) lymph

GAG components

1) Hyaluronic acid: viscous, slippery substance that binds cells together, lubricates joints, and helps maintain shape of eyeballs. Hyaluronidase is enzyme that breaks apart hyaluronic acid, causing ground substance of connective tissue to become more liquid. 2) Chondroitin sulfate: provides support and adhesiveness in cartilage,bone, skin, and blood vessels. 3) Dermatan sulfate: contained by skin, tendons, blood vessels, and heart valves. Keratan sulfate: contained by bone, cartilage, and cornea of eye. Ground substance also has adhesion proteins like fibronectin that are responsible for linking components of ground substance to one another and surfaces of cells.

Basic types of glands

1) Simple gland: no branching 2) Compound gland: branching 3) tubular glands: tubular secretory parts 4) Acinar glands: rounded secretory portions 5) Tubuloacinar glands: Both tubular and more rounded secretory parts

Epithelial Cell shapes

1) Squamous cells: thin, allows for rapid passage of substances through them. 2) Cuboidal: tall, wide, shaped like cubes. May have microvilli at apical surface and function in either secretion or absorption. 3) Columnar: taller than wide, like columns, protect underlying tissues. Apical surfaces may have cilia or microvilli, and often specialized for secretion and absorption. 4) Transitional: change shape, from squamous to cuboidal and back, as organs stretch and collapse.

Mast cells

Abundant alongside blood vessels that supply connective tissue. Produce histamine, chemical that dilates small blood vessels as part of inflammatory response. Can bind and kill bacteria.

Apocrine glands

Accumular secretory product at apical surface of secreting cell. That portion pinches off by exocytosis from rest of cell to release secretion. Remaining part of cell repairs itself and repeats process. Ex. mammary glands

Blood tissue

Connective tissue with a liquid extracellular matrix and formed elements. Extracellular matrix is called blood plasma. In blood plasma are formed elements like red blood cells, white blood cells, and platelets.

Epithelial tissue surfaces

Apical surface of epithelial cell faces surface. May contain cilia or microvilli. Lateral surfaces face adjacent cells on either side. May contain junctions. Basal surface is opposite apical surface. Deepest layer and adheres to extracellular materials such as basement membrane. Anchored by hemidesmosomes. Apical layer refers to most superficial layer of cells, and basal layer is deepest layer of cells.

Liquid connective tissue

Blood and lymph

Ground substance

Can be fluid, semifluid, gelatinous, or calcified. Contains water and assortment of large organic molecules. Polysaccharides in ground substance called glycosaminoglycans (GAG) and proteins called proteoglycans. Proteoglycans form core protein and GAGs project from protein like bristles of bush. One of most important properties of GAGs is that they trap water, making found substance more jellylike.

Muscular brief

Composed of cells specialized for contraction and generation of force. Generates heat that warms body.

Lamellae

Concentric rings of extracellular matrix that consist of mineral sals, which gives bone its hardness and compressive strength, and collagen fibers, which give bone its tensile strength. Responsible for compact nature

Difference between epithelial and connective tissues

Connective has extracellular matrix, epithelial cells tightly packed together. Connective has blood vessels, epithelial does not. Epithelial normally lining and not covered by any other tissue.

Adipocytes

Connective tissue cells that store triglycerides. Found deep to skin and around organs such as heart and kidneys.

Reticular fibers

Consist of collagen arranged in fine bundles with coating of glycoprotein, provide support in walls of blood vessels and form network around cells in some tissues, such as areolar connective tissue, adipose tissue, nerve fibers, and smooth muscle tissue. Produced by fibroblasts, much thinner than collagen fibers. Plentiful in reticular connective tissue that forms stroma or supporting framework of many soft organs.

Muscular tissue

Consists of elongated cells called muscle fibers or myocytes that use ATP to generate force. Classified into three types: skeletal, cardiac, and smooth.

Cell junctions

Contact points between plasma membranes and tissue cells. 5 types: tight junctions, adherens junctions, desmosomes, hemidesmosomes, and gap junctions

Adherens junctions

Contain plaque (dense layer of proteins on inside of PM that attaches both to membrane proteins and microfilaments of cytoskeleton). Transmembrane glycoproteins called cadherins join cels. Each cadherin inserts into plaque from opposite side of PM, partially crosses intercellular space, and connects to cadherins of adjacent cell. In epithelial cells, adherents junctions form extensive zones called adhesion belts because they encircle cell similar to way belt encircles your waist. Help epithelial surfaces resist separation during various contractile activities, as when food movers through intestines.

Desmosomes

Contain plaque and have transmembrane glycoproteins that extend into intercellular space between adjacent cell membranes and attach cells to one another. Plaque attaches to elements of cytoskeleton known as intermediate filaments, which consist of keratin. These extend from desmosomes on one side of cell across cytosol to desmosomes on opposite side of cell. Contributes to stability of cells and tissue. Spot-weld-like junctions are common among cells that make up epidermis and among cardiac muscle cells. Prevent epidermal cells from separating under tension and cardiac muscle cells from puling apart during contraction.

Central (haversian) canal

Contains blood vessels and nerves

Connective tissue repair

Continuous capacity for renewal such as bone. Connective tissue like cartilage can replenish cells less readily because smaller blood supply.

Two types of epithelial tissues

Covering an lining epithelium form outer covering of skin and some internal organs. Also forms inner linings. Glandular epithelium makes up secreting portion of glands.

Nervous brief

Detects changes in variety of conditions inside and outside the body and responds by generating electrical signals called nerve action potentials that activate muscular contractions and glandular secretions.

Macrophages.

Develop from monocytes. Have irregular shape with short branching projections and capable of engulfing bacteria and cellular debris by phagocytosis. Fixed macrophages reside in particular tissue. Wandering macrophages have ability to move throughout tissue and gather at sites of infection or inflammation.

Connective tissue cells

Embryonic mesenchymal cells give rise to connective tissue cells. Immature class of cells called blasts. Fibroblasts: in loose and dense connective. Chondroblasts: in cartilage. Osteoblasts: in bone. These retain capacity for cell division and secrete extracellular matrix that is characteristic of tissue. Mature class of cells called cyte. Mature cells have reduced capacity for cell division and extracellular matrix formation.

Lymph

Extracellular fluid that flows in lymphatic vessels. Similar to blood plasma but with much less protein. Varies in composition from one part of body to another.

Membranes

Flat sheets of pliable tissue that cover or line part of body. Majority of membranes consist of epithelial layer and underlying connective tissue layer and are called epithelial membranes. Principle epithelial membranes: mucous membranes, serous membranes, and cutaneous membrane (skin). Synovial membrane lines joints and contains connective tissue but no epithelium.

Granulation tissue

Forms across wound or surgical incision to provide framework that supports epithelial cells that migrate into open area and fill it.

Appositional growth

Growth at outer surface of tissue. cells in inner cellular layer of perichondrium differentiate into chrondroblasts. chondroblasts surround themselves with extracellular matrix and become chondrocytes. Matrix accumulates beneath perichondrium on outer surface of cartilage, causing it to grow in width. Starts later than interstitial growth.

Interstitial growth

Growth from within tissue. When cartilage grows by interstitial growth, cartilage increases rapidly in size due to division of existing chondrocytes and continuous deposition of increasing amounts of extracellular matrix by chondrocytes. As chondrocytes synthesize new matrix, they are pushed away from each other. Cause cartilage to expand from within like bread rising, which is reason for term interstitial. Occurs in childhood and adolescence.

Epithelial tissue repair

Have continuous capacity for renewal. Sometimes stem cells divide to replace lost or damages cells. These reside in protected locations in epithelia of skin and GI tract to replenish cells sloughed from apical layer, and stem cells in red bone marrow continually provide new red and white blood cells and platelets. In other cases differentiated cells can undergo cell division.

Overall restoration

If parenchymal cells accomplish the repair, tissue regeneration is possible, and near-perfect reconstruction of injured tissue may occur. If fibroblasts of stroma are active in repair, replacement tissue will be new connective tissue. This is called fibrosis. This scar tissue not specialized to perform functions of parenchymal tissue.

Two types of cartilage growth

Interstitial growth and appositional growth

Spongy bone

Lacks osteons and are columns of bone called trabecular, which contain lamellae, osteocytes, lacunae, and canaliculi.

Fibroblasts

Large, flat cells with branching processes. Present in all general connective tissues, most numerous. Migrate through connective tissues secreting fibers and some ground substance of extracellular matrix.

Synovial membrane

Line cavities of freely movable joints. Line structures that do not open to exterior. Lack epithelium. Composed of discontinuous layer of cells called synoviocytes, which are closer to synovial cavity deep to synoviocytes. Secrete some of components of synovial fluid. Lubricates and nourishes cartilage covering bones at movable joints and contains macrophages that remove microbes and debris from joint cavity.

Serous membrane

Lines body cavity that does not open directly to exterior, and covers organs that are within the cavity. Consists of areolar connective tissue covered by mesothelium. Parietal and visceral layer. Secretes serous fluid, which allows organs to glide easily over one another.

Mucous membrane

Lines body cavity that opens directly to exterior. line entire digestive, reparatory, and reproductive tracts, and much of urinary tract. Barrier against microbes and pathogens. Tight junctions connect the cells. Goblet and other cells secrete mucous which prevents cavities from drying out. Also traps particles in respiratory passageways and lubricates food as it moves through GI tract. Connective tissue layer is called lamina propria. This supports epithelium, binds to underlying structures, allows some flexibility of membrane, and affords some protection for underlying structures. Holds blood vessels in place. Things diffuse through lamina propria.

Nervous tissue repair

Lowest capacity for renewal. Normally do not undergo mitosis to replace damaged neurons.

Connective tissue extracellular matrix

Material located between widely spaced cells. Consists of protein fibers and ground substance which is material between cells and fibers. Extracellular fibers secreted by connective tissue cells.

Glands

May consist of single cell or group cells that secrete substances into ducts, onto a surface, or into blood. All glands of body are classified as either endocrine or exocrine.

Gap junctions

Membrane proteins called connexins form tiny fluid-filled tunnels called connexons that connect neighboring cells. PM or gap junctions are not fused together as in tight junctions but are separated by very narrow intercellular gap. Through connexons, ions and small molecules can diffuse from cytosol of one cell to another, but large molecules cannot. Transfer of nutrients and wastes takes place through gap junctions in avascular tissues such as lens and cornea of eye. Gap junctions allow cells in tissue to communicate with one another. In developing embryo, some of chemical and electrical signals that regulate growth and cell differentiation travel via gap junctions. Also enable nerve or muscle impulses to spread rapidly among cells.

Connective brief

Most abundant. Protect and support body and its organs. Various types of connective tissues bind organs together, store energy reserves as fat, and help provide body with immunity to disease-causing organisms.

Excitable cells

Neurons and muscle fibers exhibit electrical excitability. Action potentials can travel along plasma membrane of neuron or muscle fiber due to presence of specific voltage-gated ion channels. Neuron releases chemicals called neurotransmitters, which allow neurons to communicate with other neurons, muscle fiber, or glands.

White blood cells

Not found in significant numbers in normal connective tissues. In response to certain conditions will migrate from blood into connective tissues.

Three factors that affect tissue repair

Nutrition, blood circulation, and age.

Tissue repair: new cells

Originate from stroma, or parenchyma.

Wound dehiscence

Partial or complete separation of outer layers of sutured incision.

Muscular tissue repair

Poor capacity for renewal. Satellite cells are stem cells. Cardiac muscle lacks these.

Canaliculi

Projecting from lacunae. Networks of canals containing processes of osteocytes. Provide routes for nutrients to reach osteocytes and for wastes to leave them.

Hemidesmosomes

Resemble desmosomes, but do not link adjacent cells. Transmembrane glycoproteins in hemidesmosomes are integrins. On inside of PM, integrins attach to intermediate filaments made of protein keratin. On outside of PM, integrins attach to protein laminin, which is present in basement membrane. Thus, hemidesmosomes anchor cells not to each other but to basement membrane.

Compound acinar

Secreotry portion is rounded and attaches to branched duct. Ex. mammary glands

Endocrine glands

Secrete hormones that go directly into bloodstream

Exocrine glands

Secrete products into ducts that empty onto surface of covering and lining epithelium such as skin surface or lumen of hollow organ. Limited effects. Classified as unicellular or multicellular. Most exocrine glands multicellular. Multicellular categorized into two criteria: 1) whether their ducts are branched or unbranched. 2) the shape of secretory portion of gland.

Merocrine glands

Secretions synthesized on ribosomes, packaged by Golgi complex, and released via exocytosis. Most exocrine glands are merocrine. Ex. salivary glands and pancreas.

Compound tubuloacinar

Secretory portion is both tubular and rounded and attaches to branched duct. Ex. acinar glands of pancreas

Compound tubular

Secretory portion is tubular and attached to branched duct. Ex. bulbourethral glands

Simple acinar

Secretory portion rounded and attaches to single unbranched duct. Ex. glands of penile urethra

Neuron

Sensitive to various stimuli. Convert stimuli into electrical signals called nerve action potentials and conduct action potentials to other neurons, to muscle tissue, or to glands. Consists of cell body, dendrites, and axons.

Arrangement of cells in layers

Simple epithelium: 1) single layer of cells. Secretion and Absorption. 2) Pseudostratified epithelium: appears to have mx layers of cells, but is actually simple epithelium because all cells rest on basement membrane. May contain cilia, other goblet cells secrete mucus. 3) Stratified epithelium: consists of two or more layers of cells that protect underlying tissues in locations where their is considerable wear and tear.

Cutaneous membrane

Skin. Superficial portion called epidermis and deeper portions called dermis.

Plasma cells

Small cells that develop from type of white blood cell called B lymphocyte. Secrete antibodies. Most important part of body's immune response. Most reside in connective tissues, especially GI and respiratory tract.

Lacunae

Small spaces between lamellae and contain mature bone cells called osteocytes.

Elastic fibers

Smaller in diameter than collagen fibers, branch and join together to form fibrous network within a connective tissue. Consists of elastin and fibrillin, which adds strength and stability. Strong but can be stretched up to 150% relaxed length without breaking. Plentiful in skin, blood vessel walls, and lung tissue.

Bone tissue

Store calcium and phosphorus, house red bone marrow, and contain yellow bone marrow. Classified as either compact or spongy. Basic unit of compact bone is osteon which is divided into four parts: lamellae, lacunae, canaliculi, and central canal.

Basement membrane

Thin extracellular layer that consists of two layers: basal lamina and reticular lamina. Basal lamina closer to epithelial cells. Contains laminin, collagen, glycoproteins, and proteoglycans. Reticular lamina closer to underlying connective tissue cells called fibroblasts. Basement membranes also form surface where epithelial cells migrate during froth or wound healing, restrict passage of larger molecules between epithelium and connective tissue, and participate in filtration of blood in kidneys.

Simple branched tubular

Tubular secretory part branched and attaches to single unbranched duct. Ex. gastric glands

Simple coiled tubular

Tubular secretory part is coiled and attaches to single unbranched duct. Ex. sweat glands

Simple tubular

Tubular secretory part straight and unbranched duct. Ex. glands in large intestine

Nervous tissue

Two principle cells: neurons and neuroglia.

Collagen fibers

Very strong and resist tension, but are not stiff which allows tissue flexibility. Function varies. Often occur in parallel bundles which adds great tensile strength to tissue. Consists of collagen which is most abundant protein in body (25% of body).

Tight junctions

Weblike strands of transmembrane proteins that fuse together outer surfaces of adjacent plasma membranes to seal off passageways between adjacent cells. Cells that like stomach, intestines, and urinary bladder have many of these. Inhibit passage of substances between cells and prevent contents of organs from leaking into blood or surrounding tissues.

Holocrine glands

accumulates secretory product in cytosol. As secretary cell matures, ruptures and becomes secretory product. Ex. sebaceous gland of skin.

Epithelial tissue

consists of cells arranged in continuous sheets, in either single or multiple layers. Little interstitial space. Form coverings and linings. Have free surfaces. 3 major functions: 1) selective barriers limit/aid transfer of substances into and out of body. 2) secretory surfaces that release products produced by cells onto free surfaces. 3) Protective surfaces resist the abrasive influences of the environment.

Cartilage

consists of dense network of collagen fibers and elastic fibers firmly embedded in chondroitin sulfate, a gel-like component of ground substance. Can endure considerably more stress than loose and dense connective tissues. This is due to collagen fibers and resilience. Few cells and large quantities of extracellular matrix. No nerves or blood vessels. Secretes antiangiogenesis factor which prevents blood vessel growth. Chondrocytes occur singly or in groups within spaces called lacunae in extracellular matrix. Perichondrium surrounds surface of most cartilage and contains blood vessels and nerves and is source of new cartilage cells.

Epithelial brief

cover body surfaces and line hollow organs, body cavities, and ducts. Also form glands. Allows body to interact with both internal and external environments.