tissues Flashcards
what is a tissue
a group of similar cells with a specific structural and functional role in an organ
histology
the study of microscopic structures of tissues
what are the four primary tissue types and their general functions
- epithelial tissue - protects, absorbs, secretes, excretes, filters, senses
- connective tissue - supports, protects, binds other tissues
- nervous tissue - control, communication
- muscular tissue - movement
epithelial tissue
covers surface or lines body cavities
one or more cells thick (depends on function and location)
6 broad functions in the body:
1. protection
2. absorption
3. secretion
4. excretion
5. filtration
6. sensation
ex. taste cells, stomach, respiratory tract, blood vessels, retina (portions of it), kidneys, heart (pericardium), small intestine
basically everywhere
characteristics of epithelial tissue
- cells are very close together (held with tight junctions)
- very few blood vessels
- always associated with deeper connective tissue
^^because they get nutrients/stuff from the blood from the connective tissue. CT is highly vascularized and feeds the epithelial tissue
- high rate of mitosis
^^constantly shedding the top layer, so it needs to be replaced quickly
basement membrane
located between the epithelium and connective tissue (holds the two together)
made of collagen and adhesive glycoproteins (makes it sticky)
anchor both tissues
necessary bc the epithelium is dependent on the CT
what does it mean that epithelial cells have polarity
they have two different surfaces
1. apical surface - free surface, not attached to other cells
where the action takes place (release and absorption of stuff)
2. basal surface - attached to basement membrane
physically connects cell to basement membrane which holds it to CT
what are the differences between simple and stratified cells
generally: layer of cells, shape of cells, basement membrane
- simple epithelium has one layer of cells, stratified epithelium has more than one layer
- simple epithelium is named by the shape of cells, stratified epithelium is named by the shape of the apical cells
- in simple epithelium, all cells touch the basement membrane, in stratified epithelium, not all cells touch the basement membrane
what are the four types of simple epithelial tissue
all one cell layer thick
- simple squamos epithelial tissue
- simple cuboidal epithelial tissue
- simple columnar epithelial tissue
- pseudostratified columnar epithelial tissue
^ looks stratified, but not all cells touch the apical surface (all cells touch the basement membrane)
what are the four types of stratified epithelial tissue
2-20 layers thick, only the deepest layers are attached to the basement membrane
- stratified squamous epithelial tissue
- stratified cuboidal epithelial tissue
- stratified columnar epithelial tissue
- transitional epithelial tissue
^tissue changes shape
what are the four membranes that epithelial tissue forms
External membrane
1. cutaneous membrane
skin
Internal membranes
2. mucous membrane (mucosa)
lines passages that open to the exterior
ex. digestive, respiratory, urinary, and reproductive tracts
- serous membrane (serosa)
lines the outer surface of most organs (viscera)
ex. pleurae, pericardium, peritoneum - endothelium
internal lining of blood vessels, heart, lymph vessels
what is the connective tissue layer of the mucosa
lamina propria
mucous membranes secrete ____
mucus
what kind of epithelial cells are in serous membranes?
mucous membranes?
serous membranes are always simple squamos
mucous membranes can be different types of epithelium
serous membranes secrete ____
serous fluid
what is the function of the serosa
gets rid of friction between organs
what is the connective tissue layer of the serosa
areolar connective tissue
what are the numerous functions of connective tissue
binding of organs, support, physical protection, immune protection, movement, storage, heat production, and transportation
general features of connective tissue
cells are not very close together
can be vascularized (ex. dense irregular) or not (hyaline cartilage)
why does it take so long for a tear in fibrocartilage (ACL and meniscus) to heal?
bc its not vascularized – need blood flow to heal properly and quickly
what are the five general types of connective tissue
fibrous CT
adipose tissue
cartilage
bone tissue
blood
what are the three main elements that make up all CT
cells
fibers
ground substance
(fibers and ground substance make up the extracellular matrix
what exactly is the extracellular matrix in CT
extracellular material composed of non cellular substances, like water, proteins, carbs, gases, ions, nutrients, wastes, etc.
2 specific non cellular substances:
fibers: fibrous proteins
ground substance: viscous gel like substance made up of carbs and/or proteins that holds together body cells
function of the extracellular matrix in CT
-provides physical scaffolding for tissue
-initiates and maintains crucial physiological processes in tissues
ex. cell adhesion, water regulation, tissue growth, repair, and differentiation
-different functions depending on tissue type
ex. matrix of bone is what makes it hard (has fibers and calcium phosphate)
ex. blood matrix has no fibers, just plasma (ground substance)
fibroblasts
cells in connective tissues that produce the fibers and ground substance
what are the three types of fibers in CT
collagen, reticular, and elastic fibers
collagen fibers
made of the protein collagen
degrades as we age –> wrinkles
most abundant protein in the body (25%)
tough, flexible, resists stretching
reticular fibers
thin collagen fibers, coated with glycoproteins
bind together organs
elastic fibers
made of the protein elastin
coiled structure that allows for recoiling after stretching
abundant in arteries (need to expand and contract with blood flow)
what are the three types of ground substances in CT`
glycosaminoglycans
proteoglycans
proteoglycans & glycoproteins
glycosaminoglycans
long polysaccharides
aid in regulating electrolytes and water balance
can be as large as a cell
- they have a negative charge that attracts Na+ and other positive ions to the tissue
- water will follow the solutes
hylaronic acid is a glycosaminoglycan
- very good for skin bc it moisturizes it
condroitan lines joints
- pulls water to joints and can help with arthritis
proteoglycans
polysaccharides with proteins
slows the spread of pathogenic organisms in tissues so that the immune system can catch it
ex. fruit that is stuck in jello (pathogen that is stuck in a proteoglycan)
proteoglycans and glycoproteins
protein-carbohydrate complexes
attach CAMs (cellular adhesion molecules) to fibers in the matrix
what are the two main (and four sub) categories of fibrous connective tissue
fibrous connective tissue
1. loose connective tissue
- areolar connective tissue
- reticular connective tissue
2. dense connective tissue
- dense regular connective tissue
- dense irregular connective tissue
what is main difference between loose and dense connective tissue
loose CT has more ground substance than cells/fibers
dense CT has more cells/fibers than ground substance
general features of fibrous connective tissue
most diverse type, very conspicuous fibers
areolar connective tissue
highly vascularized
function in nutrient waste and exchange
found almost everywhere (99% of the time, it is immediately deep to epithelial tissue)
it is sticky - binding between epithelial layer and deeper CT
reticular connective tissue
function in framework for lymphatic organs
located in lymph nodes, spleen, thymus, and bone marrow
sticky - holds together lymphatic organs
like a netted bag with cells inside
dense regular connective tissue
function in binding bones and muscles
located in ligaments and tendons
fibers arranged in regular straight motion (only one direction)
dense irregular connective tissue
functions in withstanding stress, supporting epithelium (vascularized)
located in the dermis, deep to serous membranes
fibers arranged in an irregular pattern
adipose tissue
functions in filling space (between organs, etc –> gives structure) , energy storage
located in subcutaneous fat, organs, breasts, usually found deep to skin
very little matrix in between cells
cartilage (general) + name three types and their fibers
very few blood vessels
nutrition/waste exchange is slow
harder to heal
3 types (that may have specific names)
-hyaline cartilage -> collagen fibers
-elastic cartilage -> elastic fibers
-fibrocartilage -> course bundles of collagen fibers
hyaline cartilage
functions in movement and structure
located in bones, lines respiratory system (trachea, larynx, etc. – keeps airways open), ribs (connects bone to sternum)
looks glassy and reflective
covers tips of bones and joints
a precursor of bone (all bone develops from hyaline cartilage)
elastic cartilage
functions in giving a flexible structure
located in the ear (funnel of auricle), epiglottis
has conspicuous elastic fibers
fibrocartilage
functions to absorb shock and resist compression (ex. in knees)
found in intervertebral discs, menisci, and pubic symphysis
chondrocytes are in rows in lacunae
bone tissue
bone can refer to an organ or a tissue
functions in supporting, protecting, movement, Ca2+ and P storage
located in skeleton and ears
bone tissue is metabolically active
blood tissue
functions in transportation (O2, nutrients, waste, etc.), immunity (WBC), and clotting (platelets)
located in blood vessels, heart
plasma is ECM
what is excitable tissue
nervous and muscular tissue
has an electric charge that moves across the plasma membrane
nervous tissue
functions in communication
located in brain, spinal cord, and nerves
muscular tissue
3 types:
skeletal
cardiac
smooth
functions in movement in the body
