tissue types and structures

tight cell junctions

forms seals - pulls cell very tight to form impermeable seal, through strands of transmembrane proteins

adherens cell junctions

structural strength, doesn't seal it so water can go past, attaches to microfilaments

desmosome cell junctions

withstand intense mechanical stress, attaches to intermediate filament

hemidesmosome

keeps structural integrity of junctions, attaches cells to extracellular matrix

gap junctions

for rapid exchange, forms small gap between cells so small molecules can pass through, 6 connexons on each side

nervous tissue function

detects internal and external changes in conditions, acts to maintain homeostasis

2 main nerve cell types

neurones - generate and conduct impulses. neuroglia - non conducting, insulate, support and protect neurones

multipolar neurones

lots of individual dendrites for one cell body, one axon

bipolar neurones

one axon and one dendrite - two processes

unipolar neurones

one process which branches into a dendrite and an axon

skeletal muscle

long cylindrical cells containing many peripheral nuclei

striated, parallel fibres, voluntary, conscious control

cardiac muscle

found in heart walls, central nuclei, cells joined end to end via intercalated discs, striated, involuntary

smooth muscle

Involuntary, not striated, cells thick in middle and tapered at ends, central nucleus, found in hollow structure walls

epithelial tissue

form continuous sheets, covers body surfaces, lines hollow organs, forms glands, avascular, innervated, high proliferative potential

avascular

cells have no blood vessels running through them

innervated

nerves between them

simple squamos epithelial tissue

filtration or exchange via diffusion, in kidneys, capillaries, alveoli etc

simple cuboidal epithelial tissue

secretion and absorption, in kidney tubules and small glands

simple columnar epithelial tissue - non ciliated

absorption and secretion, in digestive tract, gall bladder

simple columnar epithelial tissue - ciliated

moves mucus in lungs and eggs down fallopian tubes

stratified squamous epithelial tissue

protection from abrasion, in oesophagus, epidermis

stratified cuboidal epithelial tissue

protection, secretion, absorption, in large ducts of glands

stratified columnar

protection, secretion - in urethra, ducts of some glands

transitional epithelium

permits distension - stretching, in urinary bladder, ureter

connective tissue

supports, protects and gives structure to other tissues or organs

3 types of secretion

merocrine, apocrine, holocrine

merocrine

products are secreted by exocytosis, rER - golgi - vesicle - secretion

apocrine

part of cell/cytoplasm is pinched off

holocrine

mature cell dies and becomes secretory product, cell division replaces lost cell

endocrine glands

ductless, usually secrete hormones

exocrine glands

usually found on body surface, unicellular, multicellular, simple/compound

simple multicellular

tubular/acinar, ducts don't branch

compound multicellular

branched tubular, acinar or tubuloacinar, ducts branch and separate

connective tissue function

bind and strengthen other tissue, protect/support internal organs, compartmentalise, major transport system, immune function, energy storage

connective tissue cell types

fibroblasts, chondrocytes, macrophages, RBCs, WBCs, adipocytes

extracellular matrix

consists of ground substance and protein fibres

ground substance

gel like substance present in connective tissues

3 types of protein fibres

collagen, elastic, reticular

collagen

non elastic, strong, flexible

elastic

rubbery, fibrillin and elastic

reticular

thin branched collagen with other proteins

connective tissue types

loose, dense, cartilage, bone, blood

3 types of loose tissue

areolar, adipose, reticular

loose areolar

semifluid ground substance surrounds blood vessels and nerves, all 3 protein fibre types, mostly fibroblasts, secrete fibres and ground substance

loose adipose

stores triglycerides, shock absorber, thermal insulator in subcutaneous tissue, mostly adipocytes

loose reticular

interwoven reticular fibres associate with reticular cells. forms the stroma - supporting framework in reticular organs

3 types of dense tissue

regular, irregular, elastic

dense regular

closely packed parallel collagen fibres, in areas where tension is exerted along axis of fibres

dense irregular

thick irregular collagen fibres, found where tension is exerted in many planes

dense elastic

strength and elasticity, recoils easily eg. artery walls

3 types of cartilage

hyaline, elastic, fibrocartilage

hyaline

most widely distributed, end of bones, forms articular cartilage for joint movement with low friction, shock absorber, flexible with firm suport

elastic cartilage

more elastin fibres, found where strength and elasticity are needed

fibrocartilage

parallel collagen fibres with chondrocytes squeezed between, strongest cartilage, rigid, where strong support is needed

bone

many collagen fibres and matrix of inorganic calcium salts, supports and protects soft tissue, fat storage, blood cell synthesis

blood

RBC and WBCs surrounded by fluid plasma matrix