A & P Unit 2 Exam Redone

Tissue

a group of cells found together in the body and performing a particular set of functions; they also share a common embryonic origin

Histology

microscopic examination of tissues; often used to detect pathology

The 4 types of tissue

epithelial, connective, muscle, and nervous

epithelial tissue

sheets of cells that are in contact with the outside via an internal cavity; found in the respiratory system, digestive system, and the epidermis of skin

connectiive tissue

provides protection and support

muscle tissue

responsible for movement in response to stimulus

types of muscle tissue

skeletal, cardiac, and smooth

types of connective tissue

bone, tendon, fat, and blood

nervous tissue

responsible for the propagation of nerve signals; make up the brain, spinal cord, and nerves

embryonic origin

each major cell lineage gives rise to different tissue types (Epithelial tissue is derived from all three layers, while nervous tissue comes mostly from the ectoderm and muscle and connective tissues come from the mesoderm)

connective tissue membrane

surrounds organs and lines joints (synovial membrane around joints)

epithelial tissue membrane

is attached to a layer of connective tissue, mucosa lines many systems, serosa covers organs located within body cavities; provide protection and reduce friction

serosa

cover organs not open to the outside; provide protection and reduce friction

pleura

covers the lung

pericardium

covers the heart

peritoneum

covers organs of the abdominopelvic

endothelium

type of epithelium which lines hollow organs and spaces not exposed to the outside, derives from all three germ layers, very little extracellular material between cells, joined by cell junctions

apical surfaced

exposed to lumen

basal lamina

attachment site to underlying tissue

reticular lamina

secreted by underlying connective tissue, forming a basement membrane

functions of epithelial tissue

mostly avascular and replaced rapidly, first line of defense for the body, gatekeepers for materials from the outside, secretions of compounds onto apical surface, organelles often polarized, reflecting function, cilia are common to move fluid

three common junctions of epithelial tissue

tight junctions, anchoring junctions, and gap junctions

tight junctions

block movement of substances in the ECF betwen cells, epithelia act as selective barrier

desmosomes

proteins link cells through membranes

hemidesmosomes

proteins link to ECM

adherins

actin connects cells; influences shape and folding of tissue

gap junctions

proteins form intercellular pathways between cells for the movement of molecules and ions to coordinate function (cardiac muscle)

Classifications of epithelia

simple, stratified, pseudostratified

simple epithelia

one layer

stratified epithelia

multiple layers

pseudostratified

looks like stratified, but shares a single basal layer; irregularly shaped

simple squamous epithelium

scale-shaped, thin; allows passage of chemicals (oxygen and CO2 in alveoli)

simple cuboidal epithelium

boxy, as wide as it is tall (kidney tubules)

simple columnar epithelium

rectangular, taller than it is wide (fallopian tubes)

stratified squamous epithelium

multi-layered, scale-shaped, thin; most common stratified, protects vs. mechanical damage (skin or cheek)

stratified cubodial epithelium

multi-layered, boxy, uncommon in humans (ducts of glands)

stratified columnar epithelium

multi-layered, tall (urethrae)

pseudostratified columnar epithelial

only seems multilayered, shared basal lamina, irregular (goblet cells)

transitional epithelium

cells change shape; found only in urinary bladder and associated structures

endocrine

ductless, secretions released directly into tissue

exocrine

releases secretions into ducts then to outside, may be simple (single duct) or compound (branched duct)

merocrine

most common method of secretion, vesicles released by exocytosis

apocrine

secretion accumulates near apical surface, pinches off; cell remain intact (axillary and genital sweat glands)

holocrine

entire cell ruptures, releasing secretions (sebaceous glands near hair)

connective tissue information

cells dispersed within a matrix made by the cells, matrix is made of ground substance often crisscrossed with protein fibers, usually this ground substance is fluid, but in bone, it is mineralized

functions of connective tissue

support, connect, and protect (bones and coverings), defense against microorganisms (lymph), transport nutrients and waste (blood), provide energy storage (fat)

types of loose connective tissue

areolar, adipose, and reticular

types of dense connective tissue

dense regular, elastic, and dense irregular

types of supportive connective tissue

cartilage, hyaline cartilage, fibrocartilage, elastic cartilage, and bone

types of fluid connective tissue

blood and lymph

fibroblasts

most abundant connective tissue cell, secrete ground substance

adipocytes

lipid storage (brown for quick access, white for longer storage)

mesenchymal cell

multipotent cell for repair

immune cells

include macrophages, mast cells, lymphocytes, plasma cells, and phagocytic cells

the three fibers fibroblasts secrete

collagen, elastic fibers, and reticular fibers

collagen fibers

strong but flexible, resists stretching

elastic fibers

elastin, stretchable

reticular fibers

branching, net-like; support

adipose

fat storgae, little ECM; insulation and protection

Areolar

little specialization, random, underlies most epithelia (supports vessels and organs, underlies most epithelia)

reticular loose connective tissue

mesh or net-like supportive tissue (spleen, liver)

regular dense connective tissue

parallel fibers, strong in that direction (ligaments and tendons)

elastic dense connective tissue

contains elastin, returns to original shape (vocal cords)

irregular dense connective tissue

fibers in random directions, strong in every direction (arterial walls)

chondrocytes

cartilage cells

lacunae

spaces between chondrocytes

hyaline cartilage

most common cartilage, clear, strong and flexible; nose, rib cage, bones at joints

fibrocartilage

thick bundles, tough; intervertebral discs

elastic cartilage

rigid support, elastic; ear lobes

collagen in bone

collagen thats within mineralized ground substance, hydroxyapatite, without collagen bone will shatter; without hydroxyapatite, bone would flex

osteocyte

bone cell, located within lacunae, arranged in circles around an osteon, highly vascularized

blood (fluid connective tissue)

blood cels circulate in liquid matrix (plasma)

lymph (fluid connective tissue)

liquid matrix and white blood cells

skeletal muscle tissue

locomotion, heat generation, myocye (muscle cell) is derived from the mesoderm; is striated (striped), multinucleate, voluntary

cardiac muscle tissue

forms contractile walls of the heart; cardimyocytes (heart muscle cells) are also striated, usually single nucleus, involuntary, have intercalated discs formed by anchoring junctions and gap junctions

smooth muscle tissue

lines digestive system and moves other involuntary organs; not striated, spindle shaped, one nucleus

nervous tissue

is excitable, propagates action potentials for signaling, and has a distinctive morphology

the two classes of nervous tissue

neuron and neuroglia

neuron

propagate action potentials; three parts

cell body of a neuron

contains most of the cytoplasm, organelles and the nucleus

dendrites of a neuron

branches off the cell body, contact other neurons

axon of a neuron

long “tail” along which electrochemical signal travels to the synapse (space between neurons)

neuroglia

act as support cells for neurons; four types of neuralgia

astrocytes

“star” shaped, take up and break down neurotransmitters, form blood-brain barrier

microalgia

nervous system immune cells, combat infection

oligodendrocytes

produce myelin in the central nervous system, may connect to multiple neurons

schwann cells

produce myelin in the peripheral nervous system, wrap individual axons

inflammation

initial response of the body to injury, limits injury, eliminated cause of injury, and initiates repair

necrosis

accidental cell death, causes inflammation

apoptosis

programmed cell death, does not stimulate inflammation

symptoms of inflammation

redness, swelling, pain, local heat, loss of function

the three main layers of the skin

epidermis, dermis, and hypodermis

epidermis

composed of keratinized, stratified squamous epithelium, four layers (thin skin) or fiver layers (thick, only on palms and soles), cells of the most superficial layer are dead, regularly replaced by cells from deeper layers

keratinocytes

the deepest cells of the epidermis that produce keratin

keratin

a fibrous protein

layers of the epidermis

stratum corner, stratum lucidum, stratum granulosum, stratum spinosum, and stratum basale

stratum basale (aka stratum germinativum)

attaches epidermis to the basal lamina via the basement membrane, made of cubodial basal cells, precusor to keratinocytes, also contain merkel cells (light touch receptors), melanocytes produce melanin, fingerprints result from border with dermal papillae

dermal papillae

intrude from dermis into epidermis, strengthen connection between the two

stratum spinosum

spiny due to desmosome junctions, 8 to 10 layers of keratinocytes, contains langerhans cells for immune function, and keratinocytes secrete water repelling glycolipids

stratum granulosum

grainy due to keratohyalin granules, also contain fibrous keratin, cells begin to die as nuclei disintegrate as cells migrate superficially towards the top two layers