Chapter 5: Tissues (Epithelial, Connective, Muscular, Nervous)

Anatomy & Physiology (McGraw Hill)

tissues

• groups of similar cells and extracellular material that perform a common function

• 4 types: epithelial, connective, muscular, nervous

epithelial tissue

closely packed cells with minimal extracellular matrix

• covers body surfaces

• line body cavities

• forms glands

• classified by cell layers: simple, stratified, pseudostratified

• classified by cell shape: squamous, cuboidal, columnar, transitional

characteristics of epithelia (6)

1. cellularity - cells packed tightly

2. polarity - distinctive cell surfaces (apical, lateral, basal)

3. attachment to basement membrane (barrier between epithelium and connective tissue)

4. avascularity - no blood vessels

5. innervation - supplied with nerves to detect changes in environment)

6. high regeneration capacity due to wear/tear

function of epithelia

• selective permeability

  • physical protection of internal and external surfaces

  • absorption (substances must cross to enter blood or lymph)

• secretion (glands)

• sensory reception

simple epithelium

one cell layer thick

• all cells contact base membrane

• filtration, absorption, or secretion is primary function

stratified epithelium

two or more layers of epithelia cells

• only basal layer in contact with basal membrane

• areas subjected to mechanical stress

squamous cells

flat/wide, irregular in shape, nucleus is flat with bulging center (like a fried egg)

cuboidal cell

height and width are similar, nucleus is spherical and central

columnar cell

slender and tall, nucleus is oval and oriented lengthwise in basal region

transitional cells

epithelial cells that can change shape, depending on stretch (ex: lining of bladder)

• relaxed - basal cells are cuboidal or polyhedral, apical cells are round

• stretched - apical cells flattened

• binucleated - two nuclei

simple squamous epithelium

single layer of flat cells

• thinnest barrier

• function - rapid diffusion and filtration, serous membrane secretion

• location - alveoli, endothelium (vessels walls), mesothelium/ (serous membranes)

simple cuboidal epithelium

single later of uniformly shaped cells

• function - absorption and secretion, secretory tissue of glands and small ducts

• location - kidney tubules, ovary surface, exocrine glands

simple columnar epithelium

single layer of tall cells

• function - absorption/secretion

• nonciliated - may have goblet cells or microvilli “brush border”

  • location - GI tract

• ciliated - cilia move substances across surface

  • location - fallopian tube (moving oocyte)

pseudostratified epithelium

appears as multiple cell layers, but all cells in direct contact with basement membrane

• function - protection and/or secretion

• ciliated - goblet cells secretes mucin, cilia moves/traps particles on apical surface

  • location - reparatory passageways

• nonciliated - lack goblet cells and cilia, protection

  • location - male urethra and epididymis only

stratified squamous epithelium

• apical cells are squamous, basal cells are cuboidal

• basal stem cells continuously divide to replace lost cells at surface

• function - protect underlying tissues from abrasion/friction

• keratinized - superficial layers of dead cells contain keratin and lack nuclei

  • location - skin, hair

• nonkeratinized - all cells alive, kept moist with secretions

  • location - esophagus, vagina

stratified cuboidal epithelium

• apical cells are cuboidal

• function - protection, secretion

• location - exocrine gland ducts

stratified columnar epithelium

• apical cells are columnar

• function - protection, secretion

• location (rare) - large ducts of salivary glands, conjunctiva, male urethra membrane

glands (overview)

cells or multicellular organs composed of predominately epithelial tissue

• secrete substances for use within body or elimination from body

• two types - endocrine, exocrine

endocrine glands

• lack ducts

• function - secrete hormones into blood

• location - thyroid, adrenal

exocrine glands (overview)

discharge secretions directly onto epithelial surface via ducts

• cell classification - unicellular or multicellular

• anatomic classification - simple or compound; tubular, acinar, or tubuloacinar

• secretory classification - merocine, apocrine, holocrine

unicellular exocrine gland

goblet cells

• do not contain a duct

• located close to epithelium surface

• location - simple columnar, pseudostratified columnar

multicellular exocrine gland

• ancini (“grape”) - clusters of cells that produce secretion

• ducts - epithelium-lined tube where secretions are discharged

• surrounded by fibrous capsule

• septa (extensions of capsule) partition gland into lobes

simple exocrine glands

single, unbranched duct

compound exocrine glands

branched ducts

merocine glands

• exocrine

• function - package secretions into vesicles, released by exocytosis

• location - salivary, sweat, lacrimal grands

apocrine glands

• exocrine

• function - produce their secretions when cell’s apical surface pinches off, releasing cytoplasmic content

  • cell must repair itself to regenerate secretion

• location - mammary glands

holocrine glands

• exocrine

• function - cell accumulates secretion and then disintegrates to release secretion and cell fragment

  • ruptured cells continuously displaced by epithelial cells

• location - sebaceous glands

connective tissue (overview)

• most diverse and abundant tissue, derived from mesenchyme

• function - binds, supports, protects, storage, transport, immune response

• location - tendons, ligaments, adipose, cartilage, bone, blood

• 3 components - cells, protein fiber + ground substance (extracellular matrix)

• 3 classifications - connective tissue proper, supporting connective tissue, fluid connective tissue

resident cells

cells permanently housed within connective tissue

• Fibroblasts

• Adipocytes

• Mesenchymal

• Fixed macrophages

• Mast cells

wandering cells

cells that move continuously move throughout connective tissue

• part of immune system

• help repair damaged extracellular matrix

• protect body against harmful agents

fibroblasts

most abundant resident cell in connective tissue

• structure - flat cells with tapered ends

• function - produce protein fibers and ground substance components of extracellular matrix

adipocytes

fat cell, resident cell in connective tissue

• structure - cell full of lipid droplets, nucleus pushed to edge of cell

• function - insulate, protects, stores energy

mesenchymal cells

embryonic stem cell, resident cell in connective tissue

• structure - stellate or spindle shaped

• function - divide to repair damaged tissue

fixed macrophages

resident cell in connective tissue, derived from monocytes (type of leukocyte)

• structure - large, irregular shaped

• function - engulf damaged cells or pathogens via phagocytosis, release chemicals to stimulate immune system/attract wandering cells

mast cells

resident connective tissue cell

• migrates from bone marrow

• structure - leukocytes

• function - immune response, releases pro inflammatory molecules

protein fibers in connective tissue (overview)

• strengthen and support tissue

• 3 types - collagen, reticular, and elastic fibers

collagen fiber

connective tissue protein fiber

• structure - unbranched, fibrous

• function - strong, resistant to stretching

• location - tendons, ligaments (25% of body’s protein)

reticular fiber

connective tissue protein fiber

• structure - interwoven 3D framework, thinner than collagen

  • same protein subunits as collagen, arranged differently

• function - tough and flexible

• location - stroma of organs

elastic fiber

connective tissue protein fiber

• structure - branch and rejoin (wavy appearance), contain elastin protein

• function - stretch and recoil easily

• location - skin, walls of arteries

ground substance

molecular material produced by connective tissue cells

• structure - viscous (blood), semisolid (cartilage), solid (bone)

  • GAGs pull water to change viscosity

• function - houses connective tissue cells and protein fibers

  • glycoproteins act as glue to bond connective tissue cells and protein fibers to ground substance

mesenchyme connective tissue

embryonic connective tissue

• first tissue to emerge from developing embryo

• structure

  • cells - mesenchymal cells

  • protein fiber - immature protein fibers

  • ground substance - gel-like

• location - origin tissue for all other connective tissues (proper, supporting, fluid) act as stem cells in adult connective tissue

mucous connective tissue

embryonic connective tissue

• structure

  • cells - mesenchymal cells

  • protein fibers - more immature protein fibers

  • ground substance - viscous

• location - umbilical cord only

connective tissue proper

classification of connective tissue

• subclassifications based on proportions of cells, fibers, and ground substance

  • Loose Connective Tissue - fewer cells and fibers

    • areolar, adipose, reticular

  • Dense Connective Tissue - more fibers and less ground substance

    • regular, irregular, elastic

areolar connective tissue

loose connective tissue (connective tissue proper)

• highly vascularized

• structure

  • cells - mostly fibroblasts

  • protein fiber - unconfined organization of collagen and some elastin

  • ground substance - abundant and viscous

• function - binds skin and epithelia to deeper tissues, protects/surrounds internal organs and vessels

• location - skin (papillary + subcutaneous layers), organs

adipose connective tissue

loose connective tissue (connective tissue proper)

• commonly referred to as “fat”

• highly vascularized

• structure

  • cells - adipocytes

  • protein fiber - sparse collagen and elastin hold cells together

  • ground substance - minimal

• function - generates heat, insulation, protection, energy storage

  • brown adipose - newborns

  • white adipose - adults

• location - subcutaneous layer, surrounds some organs

reticular connective tissue

loose connective tissue (connective tissue proper)

• structure

  • cells- leukocytes, some fibroblasts

  • protein fiber - reticular fibers

  • ground substance - viscous

• function - stroma (supportive framework) in lymphatic organs

• location - spleen, lymph nodes, red bone marrow

dense regular connective tissue

dense, connective tissue proper

• low blood supply, slower healing

• structure

  • cells - few fibroblasts

  • protein fiber - abundant, tightly packed and stacked collagen

  • ground substance - limited

• function - withstands stress

• location - tendons, ligaments

dense irregular connective tissue

dense, connective tissue proper

• highly vascularized

• structure

  • cells - more fibroblasts than dense regular

  • protein fibers - bundles/clumps of projecting collagen fibers

  • ground substance - more than dense regular

• function - resists stress

• location - reticular layer of dermis, epimysium covering skeletal muscle, epineurium covering nerves, periosteum covering bone, perichondrium covering cartilage, capsules around organs

elastic connective tissue

dense, connective tissue proper

• structure

  • cells - fibroblasts

  • protein fibers - branching, densely packed elastic fibers

  • ground substance - present between protein fibers

• function - stretch and recoil

• flocation - artery walls, trachea, vocal cords

cartilage

supporting connective tissue

• structure

  • cells - chondrocytes

  • protein fibers - collagen and elastic

  • ground substance - semisolid

• function - support, withstand compression

• avascular - chondrocytes secrete chemical that inhibit blood vessel growth

  • slow healing

• 3 types: hyaline, fibrocartilage, elastic

chondrocytes

mature cartilage cell

• encased in lacunae (small space in extracellular matrix)

hyaline cartilage

supporting connective tissue

• structure

  • cells - irregularly arranged chondrocytes

  • protein fibers - collagen (not visible)

  • ground substance - glycoproteins, proteoglycans, water (makes it compressible)

• function - support

• location - tip of nose, fetal skeleton, ribs, larynx, epiphyseal and articular ends of long bones

fibrocartilage

supporting connective tissue

• structure

  • cells - large chondrocytes

  • protein fibers - numerous, coarse, irregular bundles between cells

  • ground substance - sparse

• function - resists compression, shock absorber

• location - intervertebral discs, menisci of knee

elastic cartilage

supporting connective tissue

• structure

  • cells - closely packed chondrocytes

  • protein fibers - numerous, densely packed elastic fibers in weblike mesh

  • ground substance - sparse

• function - flexible and maintains shapes

• location - external ear, epiglottis of larynx

bone

supporting connective tissue

• more solid, less flexible than cartilage

• extensively vascularized

• structure

  • cells - osteocytes

  • protein - collagen fibers (osteoid)

  • ground substance - crystal deposits

• function- movement, support, protection, stores mineral, stores hematopoietic cells (red blood cell production)

• 2 types - compact, spongy

compact bone

supporting connective tissue

• “dense”; “cortical”

• form osteons - rings of lamellae (bone connective tissue)

• lamellae encircle central canal that houses blood vessels and nerves

spongy bone

supporting connective tissue

• “cancellous”; “trabecular”

• contains latticework of bone connective tissue

• strong, lightweight

• located within interior of bone

blood

fluid connective tissue

• structure

  • cells - erythrocytes, leukocytes, platelets (cellular fragments)

  • protein fibers - fibrin (helps form sticky mesh for clotting)

  • ground substance - plasma (water proteins, solutes)

• function - transportation of materials, immune response

• location - blood vessels, heart

lymph

fluid derived from blood plasma (water, protein, solutes)

• no cellular component or fragments

skeletal muscle

“voluntary”, “striated”

• structure

  • multinucleated cells

  • long and cylindrical, parallel and unbranched

• function - movement of skeleton, thermoregulation

• location - attached to bones

cardiac muscle

• structure

  • cells have 1-2 nuclei

  • short, striated appearance

  • connected by intercalated discs

• function

  • involuntary movement of heart initiated by pacemaker cells

  • intercalated discs strengthen connection and promote rapid conduction of electrical activity

• location - heart

• minimal capacity for regeneration

smooth muscle

• structure

  • short fusiform (thick in middle, tapered end) cells

  • lack striation

• function

  • involuntary contraction movement propels material through organ

  • controls size of lumen

• location - walls of hollow internal organs, GI tract, stomach, airways, urinary tract, blood vessels

nerve tissue

• structure

  • neurons have cell body, dentrites, axon

  • glial cells

• function

  • neurons - receive, process, relay nerve impulses

  • glial cells - protect, nourish, support neurons

• location - brain, spinal cord, nerves

body membranes

epithelial layer that is bound to underlying connective tissue

• forms internal lining or external covering

• 4 types: mucous, serous, cutaneous, synovial

mucous membrane

mucosa

• structure - epithelium and lamina propria (underlying connective tissue)

• function - mucus secretion, absorb material, protection

• location - lines passageways that open to external environment

serous membrane

• structure

  • mesothelium (simple squamous epithelium)

  • thin underlying areolar layer (loose connective tissue)

• function - produce thin, watery serous fluid derived from blood plasma

• location - external surface of organs

  • parietal layer: lines body cavity

  • visceral layer: lines organ surfaces

cutaneous membrane

• structure

  • keratinized stratified epithelium (epidermis)

  • underlying connective tissue (dermis)

• function - protecting organs, prevent water loss

• location - skin

synovial membrane

specialized type of connective tissue that secrete synovial fluid

• function - reduce friction between bones, distributes nutrients to cartilage and bone

• location - joints

zygote

diploid cell formed from sperm fertilizing an oocyte

blastocyst

multicellular structure formed when zygote undergoes multiple cell divisions

embryoblast

• cells that form embryo

• differentiate by 2-3 weeks development

• develop into 3 primary germ layers: ectoderm, mesoderm, endoderm

ectoderm

germ layer that develops into:

• epidermis of skin

• epidermal derivatives (hair nails, mammary glands, sweat glands)

• nervous tissue and sense organs

• pituitary gland

• adrenal medulla

• teeth enamel

• eye lens

mesoderm

germ layer tha develops into:

• dermis of skin

• epithelial lining of vessels and serous membranes

• muscle tissue

• connective tissue

• adrenal cortex

• heart

• kidneys and ureters

• reproductive organs

• spleen

endoderm

germ layer that develops into:

• epithelial lining of respiratory, GI, urinary, reproductive tracts

• liver, gallbladder

• pancreas

• thyroid/parathyroid glands

• thymus

embryonic stem cells

originate from dividing cells of zygote or embryoblast

• totipotent

  • formed from zygote

  • give rise to every differentiated cell in organism and placenta

• pluripotent

  • derived from embryoblast

  • able to mature and specialize into a cell within any body tissue (except placenta)

adult stem cells

undifferentiated stem cells after birth

• multipotent - can differentiate into restricted number of some cell types

• unipotent - can differentiate into single type of cell

hypertrophy

increase in size of existing cells in a tissue

• number of cells remains constant

• ex: muscle hypertrophy

hyperplasia

increase in number of cells in a tissue (ex: callus development)

atrophy

shrinkage of tissue by a decrease in either cell size or cell number

metaplasia

mature epithelium changes in response to environment (ex: smoker’s trachea)

dysplasia

abnormal cell development (size, shape, organization); may be precancerous or may revert back to normal

neoplasia

tumor growth from excessive cell proliferation

• benign - localized, does not spread

• malignant (cancer) - metastasizes/invades other tissues of body