Four Basic Types of Tissue
(1) Epithelial tissue (covers exposed surfaces, lines internal passageways and chambers & forms glands, (2) Connective tissue (fills internal spaces, provides structural support for other tissues, transports materials within the body & stores energy reser
Epithelial Tissue
Includes Epithelia and Glands. Most volume of tissue is from cells. Cover & lining tissue. All have compact cells with very little interstitial space. Supporting tissue is areolar.
Epithelia
Avascular cells that cover every exposed surface of body. Form the surface of the skin and line the digestive, respiratory, reproductive, and urinary tracts (all passageways that communicate with outside world)
Glands
Structures that produce fluid secretions; they are either attached to or derived from epithelia.
Epithelia Characteristics
(1) Cellularity, (2) Polarity, (3) Attachment (bound to basement membrane), (4) Avascularity (no blood cells), (5) Regeneration
Epithelia Functions
(1) Provide physical protection and lubrication (protect from abrasion, dehydration and destruction), (2) Control permeability, (3) Provide sensation, and (4) Produce specialized secretions
Microvilli on Epithelial Cells
Line internal passageways, microvilli is on exposed surfaces. Abundant where absorption and secretion take place.
Cell Junctions
Specialized areas of PM that attach a cell to another cell or to extracellular materials. Three most common types of CJ: Tight junctions, gap junctions, and desmosomes.
Tight Junction
The lipid portions of two PM are tightly bound together by interlocking membrane proteins. Inferior is a continuous adhesion belt forms a band that encircles cell and binds them to neighbors. Bands are attached to microfilaments of terminal web. So tight
Gap Junction
Two cells held together by two interlocking transmembrane proteins called connexons. (channel proteins) form a narrow passageway letting small molecules and ions pass. Common among epithelial cells.
Desmosome
CAMS and proteoglycans link the opposing plasma membranes. Very strong and can resist stretching and twisting. Formed by two cells, within each is a dense area connected to the cytoskeleton - this is what gives the desmosome and the epithelium its strengt
Spot Desmosome
Small discs connected to bands of intermediate filaments. Intermediate filaments function to stabilize shape of cell.
Hemidesmosome
Resemble half of a spot desmosome. Attaches to a cell to extracellular filaments in basement membrane. This attachment helps stabilize position of epithelial cell and anchors it to underlying tissues.
Clear Layer of Basement Membrane
Closer to epithelium containing glycoproteins and a network of fine protein filaments. Acts as a barrier that restricts the movement of proteins and other large molecules from underlying connective tissue into the epithelium.
Dense Layer of Basement Membrane
Deeper portion of basement membrane containing bundles of coarse protein fibers produced by connective tissue cells. Gives BM it's strength. Attachments between fibers of both layers hold them together and hemidesmosomes attach epithelial cells to composi
Classifying epithelia
(1) the cell shape, and
(2) the number of cell layers between the BM and the exposed surface of epithelium.
Three Epithelial Cell Shapes
Squamous, Cuboidal, and Columnar
Two Number Classifications of Epithelial Cells
Simple or Stratified
Simple Epithelium
One layer of cells covering the BM. Thin & fragile. All cells have same polarity. Little mechanical protection, located only in protected areas of body, lining internal compartments & passageways: ventral body cavities, heart chambers, & blood vessels. Al
Stratified Epithelium
Several layers of cells cover the basement membrane. Generally located in areas that are exposed to mechanical or chemical stresses, such as surface of skin and lining of the mouth.
Squamous Epithelium
Cells are thin and flat, and somewhat irregular like a jigsaw puzzle. From surface they resemble fried eggs side by side.
Simple Squamous Epithelium
Most delicate epithelium.
Functions: Reduces friction; controls vessels permeability; performs absorption/secretion
Locations: Mesothelia lining ventral cavities, endothelia lining Heart & Blood Vessels, portions of kidney tubules, inner lining of cornea,
Mesothelium
The simple squamous epithelium that lines the ventral body cavities. The pleura, peritoneum, and pericardium each contain a superficial layer of mesothelium.
Endothelium
The simple squamous epithelium lining the inner surface of the heart and all blood vessels.
Stratified Squamous Epithelium
Found where mechanical stresses are severe and are non-keratonized.
Functions: Physical protection from abrasion, pathogens, and chemical attack.
Locations: Surface of skin; lining of the mouth, throat, esophagus, rectum, vagina, and anus.
Keratin / Keratinized stratified squamous epithelium
Apical layers of epithelial cells, on exposed body surfaces where mechanical stress and dehydration are potential problems. Superficial layers are both tough and water resistant; epithelium is keratinized.
Non-keratonized stratified squamous Epithelium
Resists abrasion, but will dry out and deteriorate unless kept moist. Located in oral cavity, pharynx, esophagus, anus, and vagina.
Cuboidal Epithelium
Resemble hexagonal boxes, and appear square.
Simple Cuboidal Epithelium
Occurs where secretion or absorption takes place. Forms capsules of endocrine glands.
Functions: Limited protection, secretion, & absorption
Locations: Glands, ducts, portion of kidney tubules, thyroid gland.
Stratified Cuboidal Epithelium
Functions: Protection, secretion, absorption
Locations: Rare lining of some ducts along sweat glands and large ducts in mammary glands. (apocrine glands)
Transitional Epithelium
Flat when bladder is full & plump when bladder is empty.
Functions: Expansion & recoil after stretching without damage
Locations: Urinary bladder, renal pelvis, and ureters
Columnar Epithelial Cells
Appear rectangular, in reality they are hexagonal.
Simple Columnar Epithelial
Found where absorption or secretion occurs.
Functions: Protection, secretion, & absorption. Goblet cells.
Locations: Lining of stomach, intestine, gallbladder, uterine tubes, & collecting ducts of kidneys.
Pseudostratified columnar epithelium
Appears to be layered/stratified but is not because every epithelial cell contacts basement membrane.
Functions: Protection, secretion, move mucous w. cilia
Locations: Lining of nasal cavity, trachea, & bronchi, & portions of male reproductive tract.
Stratified Columnar Epithelia
Relatively rare
Functions: Protection
Locations: Small areas of pharynx, epiglottis, anus, mammary glands, salivary gland ducts, and uretha.
Endocrine Glands
Release endocrine secretions (hormones) into interstitial fluid and enter the bloodstream for distribution. Examples: thyroid gland, and pituitary gland. Because secretions aren't released into ducts they are also called ductless glands.
Exocrine Glands
Release exocrine secretions into passageways called ducts that open onto an epithelial surface.
Glandular Epithelial Cell Releases it's Secretions by
(1) merocrine secretion,
(2) apocrine secretion, or
(3) holocrine secretion.
Merocrine Secretion
Product released from secretory vesicles by exocytosis. Most common mode of secretion. In the skin, merocrine sweat glands produce watery perspiration that helps you stay cool. (mucin/mucous)
Apocrine Secretion
The loss of cytoplasm and secretory product. Apical portion of cytoplasm becomes packed with secretory vesicles and is shed.
Holocrine Secretion
Destroys the gland cell, in contrast to merocrine and apocrine secretions. Entire cell becomes packed with secretory products and then bursts, releasing secretion but killing cell. Further secretion depends on stem cells.
Exocrine Gland Secretions
(1) Serous glands (secrete watery solution with enzymes - parotid salivary glands), (2) Mucous glands (secrete mucins forming mucus - sublingual salivary glands & submucosal glands of small intestine), (3) Mixed exocrine glands (1+ type of gland cell & ma
Unicellular Glands & Multicellular Glands
UG: The individual secretory cells in epithelia that have independent, scattered gland cells.
And
MG: Glandular epithelia and aggregations of gland cells that produce exocrine or endocrine secretions.
Mucous (Goblet) Cells
The only Unicellular Exocrine Glands in the body. Secrete mucins and are scattered among other epithelial cells. Pseudostratified columnar epithelium lining trachea and columnar epithelium of small and large intestines have an abundance of mucous cells.
Multicellular Exocrine Gland
A secretory sheet. Gland cells form an epithelium that releases secretions into an inner compartment. In pockets set back from epithelial surface - their secretions travel through ducts. Ex. Salivary Glands.
Describing the Structure of Multicellular Exocrine Glands
(1) Structure of Duct (simple=single; duct/compound= duct divides)
(2) Shape of Secretory Portion of Gland (tubes= tubular; blind pockets= alveolar; tubes & pockets= tuboalveolar
(3) Relationship Between ducts & glandular areas. (branched=share ducts)
Simple Glands, Part One
(1) Simple tubular (intestinal glands);
(2) Simple cuboidal tubular (merocrine sweat glands);
(3) Simple branched tubular (gastric glands, mucous glands of esophagus, tongue, and duodenum);
Simple Glands, Part Two
(4) Simple alveolar/acinar (not found in adult; stage in development of simple branched glands);
(5) Simple branched alveolar (sebacous/oil glands)
Compound Glands
(1) Compound tubular (mucous glands/in mouth, bulbo-urethral glands/in male reproductive system, testes)
(2) Compound alveolar/acinar (mammary glands),
(3) Compound tubuloalveolar (salivary glands, glands of respiratory passages, pancreas)
Connective Tissue
(1) Sparse cells, large amount of interstitial space & vascular containing sensory receptors. (2) Ground substance (proteoglycans, hyaluronic acid, chondroitin sulfate) (3) Insoluble protein fibers: collagen, reticular, elastic. (4) Dense layer of basemen
Three Main Components of Connective Tissue
1) Cells, 2) Extracellular Fibers and 3) Ground Substance.
Connective Tissue Functions
Establishing a structural framework for body.
Transporting fluids and dissolved materials. *Protecting delicate organs
Supporting surrounding and interconnecting tissues
Storing energy reserves, esp. triglycerides *Defending body from invading microorgani
Connective Tissue Three General Categories
(1) Connective tissue proper
(2) Fluid connective tissues
(3) Supporting connective tissues
Connective Tissue Proper
Many cell types and extracellular fibers in syrupy ground substance. Divided into: (a) loose connective tissue, and (b) dense connective tissue (based on number of cells and properties & proportions of fibers & ground substance.
Fluid Connective Tissues
Distinctive populations of cells suspended in watery matrix containing dissolved proteins. There are two types: blood and lymph.
Supporting Connective Tissues
Less diverse population of cells than connective tissue proper. Matrix contains much more densely packed fibers. Protect soft tissues and support weight of part or all of body. Two types are: cartilage and bone.
Cartilage Matrix
A gel whose characteristics vary with predominant fiber.
Bone Matrix
Is calcified containing mineral deposits (primarily calcium salts) providing rigidity.
Permanent Resident Cells in Connective Tissue Proper
Fibroblasts, fibrocytes, adipocytes, and mesenchymal cells. Function in local maintenance repair, and energy storage.
Not Permanent Resident Cells in Connective Tissue Proper
Macrophages, mast cells, lymphocytes, plasma cells, and microphages. Function in defending and repairing damaged tissues. They migrate through healthy connective tissues and aggregate at sites of tissue injury.
Fibroblasts
Produces insoluble proteins in areolar connect tissue matrix. One of the two most abundant permanent cell of CTP & only cells always present in it. Secrete hyaluronan & proteins. Secretes proteins subunits assembled to form large extracellular fibers.
Fibrocytes
Second most abundant fixed cell in CTP. Spindle-shaped cells. Maintains dense layer of basement membrane separating epithelia & areolar tissue.
Adipocytes
AKA fat cells. Contains a single enormous lipid droplet. Resembles a class ring. Lipids constantly being broken down and replaced.
Macrophages
Large amoeboid cells scattered in matrix; engulf damaged cells or pathogens that enter tissue; sparse; when stimulated they release chemicals that activate immune system & attract many additional macrophages & other cells for immune defense. Two classes:
Melanocytes and Melanin
Synthesize & store the brown pigment melanin which gives tissues dark color. Common in epithelium of skin & connective tissues of eye and dermis of the skin.
Three Fibers in Connective Tissues
(1) Collagen
(2) Reticular, and
(3) Elastic.
Fibroblasts form all. Fibrocytes maintain these CTF.
Collagen Fibers
Long, straight, & unbranched. Most common fiber in CTP. Bundle of fibrous protein subunits wound together like rope strands. Flexible but stronger than steel. Tendons & ligaments,
Areolar & reticular CT,
Osseous tissue,
Dense Regular and Irregular tissue,
Tendons
Connect skeletal muscles to bone. Consists almost entirely of collagen fibers. Can withstand tremendous forces.
Ligaments
Connect one bone to another. Can withstand tremendous forces.
Reticular Fibers and Stroma
Same protein subunits as collagen fibers but arranged differently - are thinner. Form branching, interwoven network (stroma) that is tough, yet flexible. Resist forces from many directions. Stroma stabilizes relative positons of cells. RF also stabilize o
Ground Substance
Fills spaces between cells and surrounds connective tissue fibers. Dense.
Mesenchyme
Embryonic connective tissue. Star-shaped stem cells, respond to local injury/infection by dividing to produce daughter cells that differentiate into fibroblasts, chondroblasts, osteoblast, & macrophages.
Mucous Connective Tissue
Wharton's jelly. Loose connective tissue found in many parts of embryo, including umbilical cord.
Loose Connective Tissues
Packing materials. Fill spaces between organs, cushion, and stabilize specialized cells in many organs and support epithelia. Tissues surround and support blood vessels and nerves, store lipids, and provide route for diffusion. Include: Mucous connective
Aerolar Tissue
Most common CT in body. Viscous ground substance accounts for most volume & absorbs shocks. Presence of elastic fibers make resilient. Forms layer that separates skin from deeper structures. Padding, independent movement. Injection site for drugs since it
Subcutaneous Areolar Connective Tissue includes
Mast cells, Macrophages, Fibroblasts, Adipocytes
Capillaries in Aerolar Tissue
Deliver oxygen and nutrients and remove carbon dioxide and waste products across basement membrane.
Adipose Tissue
Fatty tissue that stores triglycerides. Adipocytes count for most volume. Packer or filler around structures.
Functions: Padding/cushions shocks, insulates & stores energy
Locations: Deep to skin, sides, buttocks, breasts, padding around eyes & kidneys
Reticular Tissue
Reticular fibers create 3D stroma.
Functions: Supporting framework
Locations: Liver, kidney, spleen, lymph nodes, and bone marrow.
Dense Connective Tissues
Most volume is fibers. Collagen fibers are dominant. Two types: Dense Irregular connective tissue & Dense Regular connective Tissue which include: Tendons, Aponeuroses, Elastic tissue, & ligaments.
Dense Regular Connective Tissues
Parallel Collagen fibers packed tightly.
Functions: Firm attachment, conducts muscles pull, reduces muscles friction & stabilizes bones position
Locations: Between skeletal muscles & bone (tendons & aponeuroses), connecting bones to another (ligaments), c
Dense Irregular Connective Tissues
Form interwoven meshwork and sheath around cartilages, capsules surround internal organs, & encloses joint cavities.
Functions: Strength to resist forces from many directions, prevents overexpansion of organs (urinary bladder).
Locations: Capsules of visc
Elastic Tissue
DRC Tissue dominated by elastic fibers.
Functions: Stabilize postions of vertebrae & penis, cushions shocks, permits expansion & contractions of organs.
Locations: Between vertebrae of spinal column (ligamentum flavum & ligamentum nuchae), ligaments suppo
Elastic Fibers, Elastin, and Elastic Ligaments
Contain protein Elastin. Branched and wavy. After stretching, returns to shape. Rare and stabilize positions of vertebrae of spinal column. Are Dense Regular Connective Tissue dominated by elastic fibers.
Three Types of Formed Elements
> Red blood cells (erythrocytes - transport of oxygen in blood, half volume of blood),
> White blood cells (leukocytes - defend from infection/disease containing
Monocytes [phagocytes],
Lymphocytes [lymph],
Eosinophils and Neutrophils [phagocytes] and
Bas
Extracellular Fluid's Three Major Subdivisions
Plasma, Interstitial fluid, and lymph.
Plasma
Confined to vessels of cardiovascular system.
Lymph
Enters lymphatic vessels. Cells of immune system respond to signs of injury or infection. Lymphatic vessels return lymph to large veins near heart. This continually recirculation of fluid is essential for homeostasis.
Chondroitin Sulfates
In matrix of cartilage; a firm gel. Form complexes with proteins in ground substance, producing proteoglycans.
Chondrocytes and Lacunae
Cartilage Cells. Only cells in cartilage matrix. Occupy small chambers known as Lacunae.
Cartilage
Avascular. Very limited repairs. Collagen, elastic, and reticular fibers. Covered with perichondrium. Nutrients delivered through matrix diffusion. Interstitial and appositional growth.
Perichondrium
Fibrous separation of cartilage to surrounding tissues. Contains two layers: (a) outer, fibrous region of DICT (provides mechanical support & protection & attaches cartilage to other structures, and (b) in inner, cellular layer (growth & maintenance of ca
Cartilage Two Growth Mechanisms
(1) Interstitial Growth
(2) Appositional Growth
Interstitial Growth of Cartilage
Cell division of chondrocytes in cartilage matrix and daughter cells producing additional matrix enlarging cartilage. Most important during development. Begins in embryo and continues through adolescence.
Appositional Growth of Cartilage
Gradually increases size of cartilage by adding to its outer surface. Cells of inner perichondrium undergo repeated division, innermost cells then differentiate into chondrocytes which begin producing cartilage matrix.
Three Major Types of Cartilage
(1) Hyaline Cartilage
(2) Elastic Cartilage
(3) Fibrocartilage
Hyaline Cartilage
Most common cartilage. Packed collagen fibers not always apparent in microscopy.
Functions: Stiff/somewhat flexible support, reduce friction between bony surfaces.
Locations: Between tips of ribs & bones of sternum, covering bone surfaces at synovial join
Elastic Cartilage
Elastic fibers make it extremely resilient and flexible. Yellowish color.
Functions: Support but tolerates distortion w.out damage returning to original shape.
Locations: Auricle of external ear, epiglottis, auditory canal, cuneiform cartilages of larynx.
Fibrocartilage
Avascular with gel-like matrix and native cells found inside lacunae. Durable/Tough.
Functions: Resists compression, prevents bone-to-bone contact, limits movement
Locations: Pads in knee joints, between pubic bones of pelvis, intervertebral discs
Bone
Matrix of calcium salts (calcium phosphate) & calcium carbonate, & collagen fibers (predominant fiber). Delivers nutrients through cytoplasm diffusion & fluid in canaliculi. Extensive repairs can be made even after severe damage. Grow thick and strong wit
Compact Bone
Entire surface of skeleton
Spongy/cacellous bone
Inside of bone. Same material as compact bone, just built different.
Osteocytes
Bone cells, found inside Lacunae.
Canaliculi
Long/slender passageways in osteocyte matrix forming branching network for exchange of materials between blood vessels and osteocytes.
Periosteum
Composed of fibrous (outer) and cellular (inner) layers. Assists in attachment of bone to surrounding tissues and to associated tendons and ligaments. Cellular layer functions in appositional bone growth and injury repair.
Epithelium Supported by Connective Tissue
(1) Mucous membranes, (2) Serous membranes, (3) Cutaneous membrane, and (4) Synovial membranes
Mucous Membranes
Line passageways and chambers that communicate with exterior (those of digestive, respiratory, reproductive and urinary tracts). Epithelial surface must be kept moist to reduce friction. Lubricated by mucous.
Laminar Propria
Areolar tissue component of mucous membrane.
Serous Membranes
Can be Parietal or Visceral. Line sealed/internal subdivisions of ventral body cavity - cavities not open to exterior. Mesothelium supported by areolar tissue. 3 types: (1) Pleura (line pleural cavities & covers lungs), (2) Peritoneum (line peritoneal cav
Cutaneous Membrane
Skin. Covers surface of body. Stratified squamous epithelium and layer of areolar tissue reinforced by underlying DICT. Thick, relatively water-proof and dry.
Synovial Fluid
Produced by synovial membrane. Inside joint cavities providing lubrication reducing friction between joints. Circulates from areolar tissue into joint cavity, then percolating through articulating cartilages providing oxygen & nutrients to chondrocytes.
Synovial Membrane
Lines joint cavity. Consists of extensive area of areolar tissue containing matrix of interwoven collagen fibers, proteoglycans, and glycoproteins.
Fasciae
Connective tissue layers and wrappings that support and surround organs. Three types of layers, (1) Superficial fascia, (2) Deep fascia, (3) Subserous fascia
Superficial Fascia
AKA subcutaneous layer or hypodermis. Areolar tissue and adipose tissue separate skin from underlying tissues and organs, providing insulation and padding
Deep Fascia
DICT. Resembles plywood. Strong, fibrous framework. Resist forces from diff. directions. DCT are interwoven binding structural elements. Bound to capsules, tendons, and ligaments. Perichondrium around cartilage, periosteum around bones, etc.
Subserous Fascia
Layer of areolar tissue lying between deep fascia and serous membranes.
Muscle Tissue
Provides muscle movement. Specialized in contraction. Three types, (1) Skeletal muscle, (2) Cardiac muscle, and (3) Smooth muscle
Skeletal Muscle Tissue
Cells long & multinucleate. Striated voluntary muscle. Muscle tissue.
Functions: Moves/stabilizes skeleton position, guards entrances & exit to digestive, respiratory, & urinary tracts, generates heat, protects internal organs.
Locations: Combined w. conn
Cardiac Muscle Tissue and Intercalated Discs
Striated involuntary muscle. Cells are short, branched, single nucleus, interconnected by intercalated discs. Limited ability to repair.
Functions: Circulates blood, maintains blood (hydrostatic) pressure.
Location: Heart only.
Cardiocyte
Cardiac muscle cell. Form extensive connections to another.
Smooth Muscle Tissue
Cells short spindle-shaped w. single nucleus, divide after injury. Nonstriated involuntary muscle.
Functions: Moves food, urine, & reproductive tract secretions, controls diameter of respiratory passageways, regulates diameter of blood vessels.
Locations:
Single Unit Smooth Muscle
Spreads by electric wave, like cardiac muscle.
Multiunit Smooth Muscle
Works like skeletal muscle. Walls of blood vessels.
Neural Tissue
AKA nervous tissue. Conduction of electrical impulses from body regions. 98% in brain and spinal cord (control center for nervous system). Two types, (1) Neurons, and (2) Neuroglia or Glial cells
Dendrites and Axons
Dendrites receive information and axons (nerve fibers) conduct that information to other cells.