chapter 4 tissue organization
DESCRIPTION
AnatomyTRANSCRIPT
Ch 4 Outline
4 major tissue types- functions, features 4 types of membranes & functions Injury Aging
Four Types of Tissues
Tissues- collections of cells that perform specific, limited functions
Histology- study of tissues
4 Types of tissue: Epithelial tissue Connective tissue Muscle tissue Neural tissue
Four Types of Tissues Epithelial tissue
Covers exposed surfaces Lines internal passageways Forms glands
Connective tissue Fills internal spaces Supports other tissues Transports materials Stores energy
Four Types of Tissues
Muscle tissue Specialized for contraction Skeletal muscle, heart muscle, and walls of
hollow organs
Neural tissue Carries electrical signals from one part of the
body to another
Epithelial Tissues
Epithelia- layers of cells covering internal or
external surfaces
Glands- structures that
produce fluid secretions, either
attached or derived from
epithelia
Characteristics of Epithelia
Cellularity- composed almost entirely of cells held together by cell junctions
Polarity- exposed surface faces exterior of body or internal space (apical) and side attached to base- (basal), structural & functional differences
Characteristics of Epithelia
Attachment- base of epithelium bound to basement membrane (basal lamina)
Avascularity- lack blood vessels, obtain nutrients by diffusion
Regeneration- damaged & lost cells continuously replaced through stem cell division, very high rates
Functions of Epithelial Tissues
Provide physical protection- abrasion, dehydration, biological/chemical agent
Control permeability- ions, nutrients
Provide sensation- sensory nerves provide info about external environment
Produce specialized secretions (glandular epithelium)- physical protection, temp regulation, chemical messengers
Specializations of Epithelial Cells
In order to perform functions, highly specialized structure- polarity: cell divided into 2 distinct regions
Apical surfaces: exposed to internal or external environment Microvilli increase absorption or secretion Cilia (ciliated epithelium) move fluid
Basolateral surfaces: Base- cellular attachment Sides- cells contact neighbors
Maintaining the Integrity of Epithelia
To be an effective barrier must form a complete cover:
Intercellular connections
Attachment to basal lamina
Epithelial maintenance and repair
Intercellular Connections Epithelial cells tightly bound together CAMs (cell adhesion molecules)- transmembrane
proteins
Intercellular cement- proteoglycans contain hyaluronan (hyaluronic acid)
Intercellular Connections
Cell junctions- form bonds with other cells or extracellular material: Occluding (tight) junctions Gap junctions Macula adherens (desmosomes)
Occluding (Tight) junctions Between two plasma membranes
Adhesion belt attaches to terminal web Prevents passage of water and solutes Isolates wastes in the lumen of GI tract
Gap junctions Allow rapid communication
Held together by connexons (channel proteins) Allow ions to pass between cells Coordinate contractions in heart muscle
Macula adherens (Desmosomes) CAMs, dense areas, intercellular cement link plasma
membranes Spot desmosomes- tie cells together & allow
bending, twisting Hemidesmosomes- attach cells to the basal lamina
Attached to cytoskeleton
Spot Desmosomes
CAMS
Intercellular cement
Small discs connected to intermediate
filaments, which function to
stabilize cell shape
Hemidesmosome
Attach cell to extracellular filaments in basal lamina
Stabilize cell position and anchor to underlying tissues
Attachment to the Basal Lamina
Lamina lucida- clear layer closest to epithelium Glycoproteins & fine protein filaments Thin layer secreted by epithelia Restricts movement of proteins from underlying
connective tissue into epithelium
Lamina densa- dense layer Thick fibers produced by connective tissue Strength and filtration
Epithelial Maintenance and Repair
Constantly replaced by division of germinative cells (stem cells) near basal lamina
Exposure to enzymes, toxic chemicals, bacteria, mechanical abrasion
Classification of Epithelia
Singular epithelium; plural epithelia
Classes of Epithelia Based on shape
Squamous epithelia: thin and flat
Cuboidal epithelia: square shaped
Columnar epithelia: tall, slender rectangles
Based on layers
Simple epithelium: single layer of cells, no polarity
Stratified epithelium: several layers of cells
Simple Squamous Epithelia Thin, flat, irregular- smooth surface Simple squamous epithelium
Absorption and diffusion Aveoli, lining body cavities, lining heart &
blood vessels
Mesothelium- lines body cavities
Endothelium- lines heart and blood vessels
Located where mechanical stress is severe- skin surface, lining of mouth, esophagus, anus
Protects against attacks Keratin- protein adds strength & water resistant
Simple cuboidal epithelium- secretion and absorption (kidney tubules)
Sratified Cuboidal EpitheliaSimple Cuboidal Epithelia
-Tolerates repeated cycles of stretching and recoiling and returns to its previous shape without damage
-Appearance changes as stretching occurs
Columnar Epithelia
Simple columnar epithelium Absorption and secretion
Pseudostratified columnar epithelium Cilia movement
Stratified columnar epithelium Protection
Pseudostratified CiliatedColumnar Epithelia
-Several cell types, varying shapes & functions-Not truly stratified-Cilia movement- nasal cavity, trachea, bronchi
Glandular Epithelia Specialized for secretion
Endocrine glands Release hormones into interstitial fluid
No ducts Thyroid gland, pituitary gland
Exocrine glands Produce secretions onto epithelial surfaces
Through ducts Saliva, sweat, tears, milk Categorized by mode & type of secretion, structure
Merocrine Secretion
Produced in Golgi apparatus Released by vesicles- exocytosis Most common secretion mode Sweat glands, salivary glands
Holocrine Secretion
Released by cells bursting, killing gland cells Gland cells replaced by stem cells Sebaceous gland- oil coating on hair
Types of Secretion by Exocrine Glands
Serous glands: watery secretions- saliva
Mucous glands: secrete mucins- mucus
Mixed exocrine glands: both serous and mucous
Gland Structure- Exocrine Glands
Unicellular glands- independent, scattered cells Mucous (goblet) cells- intestinal lining
Multicellular glands- glandular epithelia & aggregations of gland cells Structure of the duct- simple or compound
Shape of secretory portion of the gland Tubular (straight/coiled) or blind pockets
Relationship between ducts & glandular areas Branched
Compound Multicellular Exocrine Glands
Compound- duct divides one or more times on
way to gland cell
Connective Tissues
Connect epithelium to the rest of the body Dense layer of basal lamina produced by connective
tissue
Functions: Provide structure, support- bone Store energy- fat Transport materials- blood Defending body from microbes Protect organs
Have no contact with outside environment
Connective Tissues
Characteristics of Connective Tissues Specialized cells
Solid extracellular protein fibers
Fluid extracellular ground substance
Extracellular components make up the matrix
Majority of connective tissue volume
Determines specialized function
Classification of Connective Tissues Connective tissue proper- connect & protect
Many cell types & extracellular fibers in syrupy ground substance Loose & dense connective tissue (adipose, tendons)
Fluid connective tissues- transport Distinctive cell populations, watery matrix, dissolved
proteins (blood, lymph)
Supportive connective tissues- structural strength Protect soft tissue, support weight of body (cartilage, bone) Matrix- gel or calcified (bone)
Connective Tissues
Fibroblasts Fibrocytes Adipocytes Mesenchymal cells Melanocytes
Macrophages Mast cells Lymphocytes Microphages
Nine Cell Types of Connective Tissue Proper
Connective Tissue Proper Cells
Fibroblasts Most abundant cell type:
Always found in all connective tissue proper
Secrete proteins and hyaluronan (cellular cement)
Fibrocytes 2nd most abundant cell type:
Found in all connective tissue proper Maintain the fibers of connective tissue
proper
Connective Tissue Proper Cells
Macrophages “Big eaters” immune system:
Eat pathogens & damaged cells Fixed macrophages- stay in tissue Free macrophages- migrate
Adipocytes Fat cells- each cell stores a single, large fat droplet
Mesenchymal Cells Stem cells that respond to injury or infection:
Differentiate into fibroblasts, macrophages
Connective Tissue Proper Cells
Melanocytes Synthesize and store the brown pigment
melanin
Mast Cells Stimulate inflammation after injury or infection:
Release histamine and heparin
Basophils (white blood cells) also contain histamine and heparin
Connective Tissue Proper Cells Lymphocytes
Specialized immune cells in lymphatic system: B-cells (plasma cells)- produce antibodies T-cells
Microphages (neutrophils, eosinophils) Phagocytic white blood cells:
Respond to signals from macrophages & mast cells
Connective Tissue Fibers
Collagen fibers
Most common fibers in connective tissue proper
Long, straight, unbranched
Strong and flexible
Tendons & ligaments
Connective Tissue Fibers
Reticular fibers Network of interwoven fibers- stroma Strong & flexible Stabilize functional cells (parenchyma) &
blood vessels, nerves Sheaths around organs
Connective Tissue Fibers
Elastic fibers
Contain elastin
Branched and wavy Return to original length after
stretching
Elastic ligaments of vertebrae
Connective Tissues
Ground Substance
Clear, colorless, viscous (thick)
Fills spaces between cells & slows pathogen
movement
Embryonic Connective Tissues
Not found in adults
Mesenchyme Embryonic stem cells 1st connective tissue
in embryos Gives rise to all other
connective tissue
Embryonic Connective Tissues
Mucous connective tissue Wharton’s jelly Loose embryonic
connective tissue
Loose Connective Tissues
Packing materials of the body
Fill spaces between organs, cushion, stabilize specialized cells in organs, support epithelia, blood vessels, nerves, store lipids
Three types in adults Areolar Adipose Reticular
Areolar TissueLoose Connective Tissues
Least specialized
Open framework Viscous ground substance
most volume
Elastic fibers
Holds blood vessels & capillary beds
Under skin (subcutaneous layer), padding
Adipose TissueLoose Connective Tissues
Contains many adipocytes (fat cells)
Types of adipose tissue White fat:
Most common Stores fat, absorbs shocks, slows heat loss (insulation)
Brown fat: More vascularized Adipocytes have many mitochondria When stimulated by nervous system, fat break down
accelerates, releasing energy Energy absorbed from surrounding tissues- heats body
Adipose Tissue
Adipose cells Adipocytes in adults do not divide:
Expand to store fat
Shrink as fats are released
Mesenchymal cells divide and differentiate: Produce more fat cells when more storage is
needed
Reticular TissueLoose Connective Tissues
Provides support Complex, 3D network- stroma
Support functional cells (parenchyma) Reticular organs
Spleen, liver, lymph nodes, and bone marrow
Dense Connective Tissues
Connective tissues proper, tightly packed with high numbers of collagen or elastic fibers
Dense regular connective tissue
Dense irregular connective tissue
Elastic tissue
Dense Regular Connective Tissues
Tightly packed, parallel collagen fibers Tendons- attach muscles to bones Ligaments- connect bone to bone & stabilize organs Aponeuroses- tendinous sheet that attaches a broad,
flat muscles to another muscle or
Dense Irregular Connective Tissues
Interwoven networks of collagen fibers
Strengthen &support areas subjected to stress from multiple directions, gives skin strength
Sheaths cartilage- perichondrium Sheaths bones- periosteum
Form capsules around some organs (liver, kidneys, spleen)
Elastic TissueDense Regular Connective Tissues
Made of elastic fibers
Elastic ligaments of spinal vertebrae
Fluid Connective Tissues
Blood & lymph Watery matrix of dissolved proteins Fluid Elements- extracellular
Plasma Interstitial fluid Lymph
Formed Elements- specific cell types Formed elements of blood
Red blood cells- erythrocytes White blood cells- leukocytes Platelets
Connective Tissues
Lymph- extracellular fluid
Collected from interstitial space
Monitored by immune system
Transported by lymphatic
system
Returned to venous system
Fluid Tissue Transport Systems
Cardiovascular system (blood)
Arteries
Capillaries
Veins
Lymphatic system (lymph)
Lymphatic vessels
Supportive Connective Tissues
Support soft tissues and body weight Cartilage - gel-type ground substance
For shock absorption and protection
Bone- calcified (made rigid by calcium salts, minerals) For weight support
Cartilage Characteristics
Cartilage Matrix- firm gel contains proteoglycans derived from chondroitin sulfates complexed with ground substance proteins Chondrocytes (cartilage cells)- occupy small
chambers- lacunae
Cartilage Structure- no blood vessels, exchange by diffusion only Chondrocytes produce antiangiogenesis factor
Perichondrium- sets cartilage apart from surrounding tissues
Outer, fibrous layer- strength Inner, cellular layer- growth and maintenance
Interstitial Growth of Cartilage
*Most important during
development
- Enlarges cartilage from
within
Hyaline Cartilage
Hyaline cartilage (most common) Stiff, flexible support Reduces friction between bones Found in synovial joints, rib tips, sternum, trachea,
elbows, knees
Elastic Cartilage
Elastic cartilage Supportive but bends easily Found in external ear and epiglottis
Fibrous Cartilage
Fibrous cartilage (fibrocartilage) Limits movement Prevents bone-to-bone contact Pads knee joints Found between pubic bones and intervertebral discs
Bone (Osseous) Tissue
Strong (calcified: calcium salt deposits) Resists shattering (flexible collagen fibers)
Osteocytes (bone cells)- in lacunae Arranged around central canals within matrix Small channels through matrix (canaliculi) access
blood supply
Periosteum Covers bone surfaces except in joint cavities Fibrous layer Cellular layer
Supportive Connective Tissue- Bone
Matrix- mixture of calcium salts (calcium phosphate, carbonate) and collagen fibers
Membranes
Membranes- physical barriers that line or cover portions of the body Consist of epithelium supported by connective
tissues
Four Types of Membranes Mucous membranes Serous membranes Cutaneous membrane Synovial membranes
Mucous Membranes
Line passageways with external connections Digestive, respiratory, urinary, reproductive tracts
Epithelial surfaces must be moist Reduce friction & facilitate absorption and excretion
Lamina propria- areolar tissue
Serous Membranes Line cavities not open to outside Thin but strong Have fluid, transudate, to reduce friction Parietal portion- covers cavity Visceral portion, serosa- covers organs
Three Serous Membranes
Pleura: Lines pleural cavities Covers lungs
Peritoneum: Lines peritoneal cavity Covers abdominal organs
Pericardium: Lines pericardial cavity Covers heart
Synovial Membranes
Articulating joint cavities (bones very close or touching) Produce synovial fluid (lubricant)- joint movement is
important in stimulating formation & circulation of fluid
Protect the ends of bones
Internal Framework of the Body
Connective tissues Provide strength and stability Maintain positions of internal organs Provide routes for blood vessels, lymphatic vessels,
and nerves
Fasciae (singular form is fascia)
Connective tissue layers surround, support organs Three types of fasciae
– Superficial fascia– Deep fascia– Subserous fascia
Muscle Tissue
Specialized for contraction
Produces all body movement
Three types of muscle tissue Skeletal muscle
Large body muscles responsible for movement
Cardiac muscle
Found only in the heart
Smooth muscle
Found in walls of hollow, contracting organs (blood vessels; urinary bladder; respiratory, digestive,
reproductive tracts), contractility & support
Classification of Muscle Cells
Striated- muscle cells with a banded appearance
Nonstriated- not banded; smooth
Muscle cells- single nucleus or multinucleate
Muscle cells can be controlled voluntarily or involuntarily
Striated Muscle Nonstriated Muscle
Muscle Tissue- Skeletal Long, thin, very large- muscle
fibers Several hundred nuclei! Do NOT divide New fibers- myosatellite cells Striated voluntary muscle-
nervous system
Muscle Tissue- CardiacCardiac cells- cardiocytesForm branching networks connected at intercalated discsRegulated by pacemaker cellsStriated involuntary muscle
Muscle Tissue- Smooth
Smooth muscle cells Small and tapered Divide and regenerate No striations
Nonstriated involuntary muscle
Neural Tissue
Specialized for conducting electrical impulses
Rapidly senses internal or external environment
Processes information and controls responses
Central nervous system Brain Spinal cord
Two Kinds of Neural Cells
Neurons Nerve cells Perform electrical communication
Neuroglia Supporting cells Repair and supply nutrients to neurons
Cell Parts of a Neuron Cell body- nucleus Dendrites- short branches extending from cell body
Receive incoming signals
Axon (nerve fiber)- long, thin extension of cell body Carries outgoing electrical signals
Tissue Injuries and Repair
Tissues respond to injuries to maintain homeostasis
Cells restore homeostasis with two processes
Inflammation- tissues 1st response to injury Regeneration
Inflammation
Inflammation = inflammatory response
Inflammatory response (signs & symptoms): Swelling
Redness
Heat
Pain
Can be triggered by trauma (physical injury) or infection
Process of Inflammation Damaged cells release chemical signals into
surrounding interstitial fluid Prostaglandins, proteins, potassium ions
Process of Inflammation
Damaged cells break down, lyse- contents leak out Lysosomes release hydrolytic enzymes Tissue destruction surrounding tissues- necrosis
Process of Inflammation
Necrotic tissues and cellular debris (pus) accumulate in the wound Abscess: pus trapped in an enclosed area
Process of Inflammation
Dilation of blood vessels (redness & heat) Increases blood circulation Brings more nutrients and oxygen to the area Removes wastes
Plasma diffuses into the area Swelling and pain
Phagocytic white blood cells Clean up the area- damaged cells, pathogens
Regeneration Injury or infection is cleaned up healing begins Fibrocytes move into necrotic area
Lay down collagen fibers- bind area together (scar tissue)
New cells migrate into area or mesenchymal stem cells produce them
Not all tissues can regenerate Epithelia & connective tissues regenerate well Cardiac cells & neurons do not regenerate (or regenerate
poorly)
Aging and Tissue Tissue repair speed, efficiency decreases with age:
Slower rate of energy consumption (metabolism) Hormonal alterations Reduced physical activity
Chemical & structural tissue changes Thinning epithelia and connective tissues Increased bruising and bone brittleness Cardiovascular disease- cumulative damage Mental deterioration
Aging and Cancer Incidence
Cancer rates increase with age 1 in 4 people in US develops cancer Cancer is the #2 cause of death in US Environmental chemicals, cigarette smoke
cause cancer Longer exposure, accumulate mutations
– 7 mutations in 1 cell
Plastics (food); pesticides (air, water, soil, food); air pollution (industry, vehicles)