2: Tissues Flashcards
4 different tissues
epithelia, connective, muscle, neural
epithelia tissue
covers exposed surfaces
lines internal passageways and chambers
produces glandular secretion
many layers of cells
classified according to number of cell layers and shape
key features in epithelial cells
cell junction - joins two cells
cilia - hair like structures on top
microvilli - smaller hair like structures to increase surface area
basement membrane - connects to basal surface
apical surface = top surface, may be open to outside world
mitochondria, nucleus, Golgi apparatus
no blood vessels
4 functions of epithelia
provide physical protection
control permeability
provide sensation
produce specialised secretions (exocrine secretions discharged onto surface, endocrine secretions released into surrounding tissue and blood)
cell junctions
tight junction = lipid layers of adjacent plasma membranes tightly bound by interlocking membrane proteins
gap junction = two cells held together by embedded membrane proteins
simple squamous
linings e.g. blood vessel
reduce friction, used for absorption and secretion
thin flattened cells = smooth surface
good for diffusion
stratified squamous
found where mechanical stresses are severe e.g. skin
physical protection from abrasion, pathogens, chemicals
more layers of cells for more protection
simple cuboidal
lining glands
secretion and absorption
large cells for organelle
stratified cuboidal
relatively rare
along ducts of sweat glands
simple columnar
protection, secretion, absorption
lines stomach and intestinal tract
stratified columnar
relatively rare
along portions of pharynx, epiglottis, anus
only top layer of cells columnar
pseudostratified ciliated columnar
appear layered but in fact all connect to the basement membrane
line nasal cavity, trachea, bronchi
move mucus with cilia
transitional epithelium
stratified epithelium that tolerates repeated cycles of stretching and recoiling
e.g. lining of uterus and bladder
exocrine glands
produced exocrine secretions through a duct onto a surface
classified as unicellular or multi-cellular
multi-cellular further classified by branching pattern of duct and it’s shape (tubular, coiled, branched, alveolar)
methods of secretion
merocrine = product released from secretory vesicles by exocytosis, most common method
apocrine = loss of both cytoplasm and the secretory product, outermost portion of cytoplasm becomes packed with secretory vesicles before shedding
holocrine = entire cell packed with secretory vesicles then bursts, releasing the secretion but killing the cell
types of secretion
serous glands = secrete watery solution containing enzymes
mucous glands = secrete mucins that form think slippery mucus
mixed glands = contain more than one type of gland cell
connective tissue
3 basic components: specialised cells, extracellular protein fibres and fluid known as ground substance
matrix = extracellular fibres and ground substance
never exposed to outside environment
highly vascular - many blood vessels
functions of connective tissue
support and protection
transportation of minerals
storage of energy reserves
defence of the body
3 major types of connective tissue
connective tissue proper = tissue under skin, can be loose or dense
fluid connective tissues = blood and lymph
supporting connective tissues = cartilage and bone
connective tissue cells
fibroblasts = always present, produce connective tissue fibres and ground substance, fibrocytes maintain the connective fibres
macrophages = engulf damaged cells or pathogens
adipocytes = fat cells, large lipid droplet
mast cells = contain histamine and heparin, chemicals released to begin body’s defensive activities after injury or infection
connective tissue fibres
formed by protein subunits secreted by fibroblasts
collagen fibres = long, straight, unbranched, strong but flexible, most common in connective tissue proper
elastic fibres = contain protein elastin, branched and wavy, return to original length after stretching
reticular fibres = thin, same protein subunits as collagen but arranged differently
loose connective tissues
fill internal spaces
provide cushioning and support epithelia
anchor blood vessels and nerves
store lipids
can be areolar, adipose or reticular tissue
areolar tissue
separates skin from deeper structures
padding, flexible
extensive blood supply
adipose tissue
fat tissue - lots of adipocytes
paddings and shock absorption
insulation to slow heat loss, stores energy
common under the skin of the flanks, breasts and buttocks
reticular tissue
reticular fibres from a complex 3D network
found around spleen and liver
supporting framework
dense connective tissues
tough, strong, durable
resist tension and distortion
interconnect bones and muscles
mostly made of collagen fibres
two types: irregular and regular
dense regular connective tissue
collagen fibres parallel to each other, packed tightly
tendons and ligaments
stabilises bone positions
reduces friction between muscles
dense irregular connective tissue
interwoven meshwork in no pattern
strengthens and supports areas subjected to stressed from many directions
covers bone and cartilage
forms thick fibrous layer (capsule) surrounding internal organs
fluid connective tissues
blood and lymph contain distinctive collections of cells in a fluid matrix
watery matrix for blood is plasma
blood = RBC, WBC, plasma and platelets
supporting connective tissues
cartilage and bone
provide supporting framework that supports rest of body
cartilage
firm gel containing embedded fibres
chondrocytes are only cells within cartilage
they occupy small pockets known as lacunae
avascular
cartilage structures covered in perichondrium made up of an inner cellular layer and an outer fibrous layer
3 types of cartilage: hyaline, elastic and fibrocartilage
hyaline cartilage
most common
closely packed collagen fibres - makes it tough by somewhat flexible
connects ribs to sternum
supports conducting passageways of respiratory tract
covers opposing bone surfaces within joints
elastic cartilage
elastic fibres - makes it resilient and flexible
external ear
epiglottis
fibrocartilage
little ground substance
matrix dominated by collagen fibres - densely interwoven making it extremely durable and tough
pads of fibrocartilage between spine, pubic bones, around tendons to absorb shock and prevent bone to bone contact
bone
matrix consists of mainly hard calcium compounds and flexible collagen fibres
strong and resistant to shattering
lacunae in the matrix contain bone cells (osteocytes)
tissue membranes
tissue membrane = physical barrier that covers body surfaces
consists of epithelium supported by connective tissue
mucous membranes
line passageways and chambers
epithelial surfaces kept moist either by mucus or by fluids
simple epithelia with absorptive or secretory functions
coated with secretions of mucous glands
serous membranes
consists of simple epithelium supported by areolar tissue
reduce friction between opposing surfaces
friction reduced by watery serous fluid
cutaneous membrane
the skin
stratified squamous epithelium and a layer of areolar tissue reinforced by underlying dense irregular connective tissue
thick, relatively waterproof
synovial membranes
line joint capsules
primary areolar tissue and an incomplete layer of epithelial tissue
muscle tissue
specialised for contraction
muscle cells contract due to interactions between filaments of the proteins myosin and actin
skeletal muscle tissue
contains very large, multinucleated cells
skeletal muscle cell may be 100 micrometres in diameter and up to 1 ft long
actin and myosin filaments organised into repeating patterns that give the cells striated appearance
partially repair after injury
voluntary
cardiac muscle tissue
found in the heart
striated
cardiac muscle cells smaller than a skeletal muscle fibre and have one nucleus
cells interconnected at intercalated discs
pacemaker cells regulate contraction
limited ability to repair
involuntary
smooth muscle
walls of blood vessels and organs
smooth muscle cell is small and slender
actin and myosin filaments scattered throughout cytoplasm so nonstriated
regenerates after injury
contractions triggered by neural activity
involuntary
nervous tissue
specialised for propagation (movement) of electrical impulses
98% nervous tissue in brain and spinal cord
neurons = have cell body containing large nucleus, numerous branching projections called dendrites and one projection called an axon
dendrites receive information and axons carry that info
neuroglia = supporting cells, maintain chemical composition of nervous tissue fluids, supply nutrients to neurons, defend the tissue from infection
response to tissue injury: inflammation
area is isolated from neighbouring healthy tissue while damaged cells, tissues and microorganisms are cleaned up
swelling, heat, redness, pain
red and warm = dilated blood vessels cuased by mast cells
swelling = diffusion of blood plasma
pain = mast cells stimulate sensory nerve endings
response to injury: regeneration
second phase following inflammation
damaged tissues replaced or repaired to restore normal function
fibroblasts produce dense network of collagen fibres known as scar tissue
epithelia, connective tissue (except cartilage) and smooth muscle tissue regenerate well
fibrosis = permanent replacement of normal tissue by fibrous tissue
aging
speed and effectiveness of tissue repairs decrease
rate of energy consumption generally declines
hormonal alterations
alter structure and chemical composition of many tissues
epithelia get thinner and connective tissues more fragile
cancer rates increase
