Topic 2a: tissues

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Tissues: group of similar cells that perform a specialized function, building blocks of organs

epithelial

connective

muscle

nervous

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Epithelial tissue:

found on the surface of any part of the body in contact with the environment; cover the outside of organs and line their lumens as well

generally, epithelial cells replicate and regenerate faster than other cell types

cells connected directly one to another in sheets or layers

basement membrane of sticky polysaccharides and proteins made by the cells attaches the tissue to other underlying tissues.

epithelial tissue always has 2 names: one for the shape of the cell and one for the layers

cell shape

squamous: flat, centrally located nucleus; suited to diffusion and lining organs and protection, formation of skin

cuboidal: cube-shaped, centrally located nucleus; typically function in secretion (ex: mucus or digestive enzymes), and also in absorption in digestive tract

columnar: oblong-shaped, typically function in secretion (ex: mucus or digestive enzymes), and also in absorption in digestive tract

pseudostratified columnar epithelia: appear stratified because there appears to be more than 1 row of nuclei, giving the impression of multiple cell layers, however it actually is one layer with the nuclei at different levels

goblet cells: simple columnar cells that secrete mucus

# of layers

simple: single layer of cells; typically columnar and cuboidal cells in this arrangement; squamous cells in this arrangement are known as endothelium

stratified: multiple layers of cells; typically squamous cells in this arrangement

transitional epithelia: in the urinary system, arranged in stratified layer, has the ability to stretch and transitions from thick to thin as the bladder fills with urine

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Connective tissue:

provides support and shock absorption

many varieties with diverse functions, but have the commonality of cells scattered in a nonliving matrix separated from surrounding tissues.

matrix is made up of ground substance, which is made up of organic (protein fibers) and inorganic material (mineral or water)

fibroblasts: main cell type that produces matrix protein fibers

collagen: type of matrix fiber that provides strength to the tissue to prevent it from being torn or separated from surrounding tissue

elastic: type of matrix fiber with lot of stretchability, made of elastin

reticular: type of matrix fiber that form a network to support the tissue and other organs that it is connected to

types of connective tissue:

loose

fibrous/dense

cartilage

blood

bone

lymph

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loose connective tissue: aka areolar, loosely packed collagen and elastic fibers surrounding fibroblasts. found around blood vessels as well as around and between most organs, filling body cavities

adipose tissue is a specialized form that stores fat and provides insulation

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fibrous (aka dense) connective tissue: contain large amounts of collagen fibers and little cells or matrix materials, can be arranged in regular (found in tendons and ligaments) or irregular (found in areas that face a lot of stress, like the dermis of the skin) arrangements

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Cartilage: a type of connective tissue made of chondrocytes, cells that make the matrix and fibers of the tissue found in the lacunae (spaces within the tissue)

hyaline cartilage: some collagen and elastic fibers, lacunae randomly scattered throughout the tissue; found in ribs, tracheal rings, and in outer parts of the nose. Glassy appearance, weakest type of cartilage.

elastic cartilage: large amount of elastic fibers, lot of flexibility, found in ears and parts of the larynx

fibrocartilage: large amounts of collagen fibers allowing those tissues to withstand a lot of stress and have shock absorption, found in intervertebral discs

cartilage type can change over time

hyaline cartilage found in movable joints like the knee, when damaged with age or trauma, is replaced by fibrocartilage, making joints feel "stiff"

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Muscular tissue:

types

cardiac: striated, involuntary control

skeletal: striated voluntary control

smooth: involuntary control

all made of bundles of muscle cells and have the ability to contract and contain many mitochondria

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Nervous tissue:

types:

neurons: communicate with each other and other cells in the body

mature neurons are unable to perform mitosis themselves

have a cell body with axons and dendrites projecting off it

cell body: contains nucleus and most of the organelles

dendrites: pick up messages and send them to the cell body

axons: send out messages processed by the cell body

many axons have schwann cells wrapped around them. Schwann cells secrete myelin and form myelin sheaths

myelin sheaths: insulate the axon and help propagate impulses faster

nodes of ranvier: gaps in the sheath where impulses jump from node to node

synapse: the space between a dendrite and the end of an axon

glial cells: support functions to neurons

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Membranes in the body: an association between tissue types

serous membranes: made of epithelial and connective tissues, line internal body cavities and cover organs

mucous membranes: made of epithelial and connective tissues, secrete mucus onto surfaces of the body in contact with the outside environment (mouth, nose, trachea, and digestive tract)

cutaneous membranes: aka skin, outer layers are made of connective and epithelial tissue