tissues Flashcards
what are the 4 types of tissue?
connective tissue
nervous tissue
muscle tissue
epithelial tissue
characteristics of epithelial tissue
- highly cellular
- bind to each other and to the basememnt membrane via adhesions or junctions
- avascular -> lacks blood vessels
- can be regenerated
- can be derived from all 3 germinal layers (ectoderm, endoderm, mesoderm)
why are epithelial cells polarised?
they have distinct cell surfaces that differ structurally and functionally
what do polarised epithelial cells form?
a continuous layer that protects and seperates the inside of our bodies from the outside environment
what are the three surfaces of epithelial cells?
- free apical surface
- lateral surface
- basal surface
free apical surface
- not attached to other cells
- often lines the lumen of ducts and cavities
- projects towards external surface / lumen
lateral surface of epithelial cells
- attached to other epithelial cells
- orients perpendicularly to the apical and basal membranes
basal surface / basal epithelial cells
attached to the basement membrane
basement membrane
- attaches epithelia to underlying tissues
- seperates tissue and protects them from mechanical stress
e.g. seperates layers of stratified squamous epithelial cells from lamina propria
apical specialisations
- microvilli
- stereocilia
- cilia
microvilli
cytoplasmic protrusions
- often found on epithelium lining internal passages
- increases surface area e.g. intestines
stereocilia
similar to microvilli but longer
- non-motile
- limited distribution to epididymis/vas deferens & sensory cells in the ear
- male reproductive tract
cilia
motile hair-like protrusions
- hundreds per cell
- coordinated beats to move substances
- found in respiratory epithelium & fallopian tubes
- reduced cilia movement -> less mucous movement = reduced protection against bacteria
what are tissues?
group/layer of specialised cells that work together and perform certain functions
- all types of tissues are present in most organs
- they each consist of cells and extracellular materials
basolateral specialisations
epithelial cells are very cohesive and close together.
- specialisations = junctions (between cells and underlying basememt membrane)
these junctions help to: - maintain polarised state
- join cells together
- exchange information and metabolites
occluding/tight junctions
seals cells together to prevent leaking
located at top of cell - closer to microvilli
- zona occludens = apical part of lateral domain, almost fusing two cells together
anchoring junctions
mechanically attaches cells to the neighbouring cells
abundant in tissues that experience extreme stress e.g. skin / cardiac muscle
- zona adherens= strong junctions that join cells at lateral domains
- hemidesmosome = strong at basal domain to allow the stable adhesion of basal epithelial cells to the underlying basement membrane
communicating/gap junctions
allows the passage of chemical or electrical signals through the cell
epithelial cell functions
- protecting underlying structures
- allowing passage of certain substances
- barrier to prevent movement of unwanted substances
- secretion of substances
- provide sensations
classification of epithelial cells
number of layers
- simple = single layer -> good for absorption
- stratified = 2 or more layers -> good for protection
- pseudostratified = 1 layer of a mixture of cell shapes
shapes of cells
- squamous = flat
- cuboidal = cube shape
- columnar = tall cylindrical shaped
- transitional = readily change shape -> stretching
surface specialisations
- cilia
- keratin
epithelial tissue names
= number of layers + shape of cell at free surface
simple squamous
structure:
- single layer
- flat, hexagonal cells
- flat nuclei
function:
- diffusion
- secretion and absorption
- barrier / protection against friction
location:
- lining of blood vessels & heart & alveoli…
simple cuboidal
structure:
- single layer, cube-shaped cells
- some have microvilli or cilia
function:
- diffusion
- secretion & absorption
- movement of particles in mucous out of e.g. bronchioles by ciliated cells
location:
- kideny tubules
- glands
- lining of terminal bronchiolesn in lungs
- ducts and areas where secretion occurs in small glands
lamina propria
loose connective tissue found under thin layer of tissues covering a mucous membrane
simple columnar
structure:
- single layer of tall, narrow cells
- some microvilli or cilia
function:
- movement of substances
- absorption & secretion
- more protection that the flat squamous cells
location:
- glands and some ducts
- brochioles of the lungs
- stomach, intestines..
stratified squamous
structure:
- multiple layers of cells that are cube-shaped in basal layer and get flatter towards the surface
- nonkeratinized (moist) or keratinized
- thicker = protection
function:
- protection against abrasion
- barrier against infection
- reduced water loss
location:
- keratinized = skin
- non-keratinized = mouth, larynx, anus…
stratified cuboidal
structure:
- multiple layers of cube-shaped cells
function:
- secretion & absorption
- protection against infection
location:
- rare
- sweat gland ducts
- ovarian follicular cells, salivary gland ducts
stratified columnar
structure:
- multiple layers of cells with tall, thin cells on layers of more cube-shaped cells
- ciliated in larynx
function:
- protection
- secretion but NO ABSORPTION
location:
- mammary gland ducts
- larynx
pseudostratified columnar
structure:
- single layer (some reach free surface, some do not)
- nuclei at different levels
- appears stratified
- almost always ciliated & associated to goblet cells
function:
- synthesize, secrete & move mucous
location: - lining of nasal cavity, pharynx, trachea
transitional epithelium
- cell shape & number of layers depend on how stretched it is
- non stretched = cuboidal or columnar
- stretched = flattened or squamous
- as stretches -> cells shift on one another so number of layers decreases
- accomodate fluctuations in volume of fluid in organs or tubes
- protection against caustic effects of urine -> lining of urinary bladder
keratin
nonkeratinized (moist) = layers of fluid covering outermost layers of cells
-> mouth, throat, anus, vagina
keratinized = living cells in deepest layers, outer layers contain keratin (dead)
-> tissue = dry, durable, moisture-resistant
-> skin, gums…
has extra protection e.g. from burns
keratin: tough and fibrous protein
-> forms intermediate filaments that give structure to epithelial cells
smoking
normal columnar epithelium -> squamous metaplasia
connective tissue
- abundant
- makes up part of every organ in the body
- cells seperated by extracellular matrix
- connections and support (ligaments and tendons, bone and cartilage)
- cushioning, insulation &storage (adipose tissue)
- transport (blood)
- provides environment where exchange of nutrients and gases can occur
types of connective tissue
- connective tissue proper (loose, dense)
- supporting connective tissue (cartilage, bone)
- fluid connective tissue (blood, haemopoietic tissue)
tendons
bone to muscle
ligaments
bone to bone
what specific connective tissue are ligaments and tendons composed of?
collagenous connective tissue
which 3 fibres make up the extracellular matrix?
- collagen
- reticular
- elastic
collagen fibres
- abundant protein
- can form elongated bundles of fibres, sheets and networks
- strong and flexible
- straight and thicker
- type 1: most abundant -> ligaments and tendons
- type 2 -> cartilage
- type 3 -> reticular fibres
elastic fibres
- secreted by fibroblasts
- branching networks in ECM
- thinner
- in areas where greater elasticity is needed e.g. lungs, blood vessel walls
reticular fibres
- type 3 collagen fibre
- branch extensively -> form networks to fill spaces between tissues and organs
- allow more give than collagen fibres
- found in liver, spleen and lymph nodes
resident cells
reside in the place they are found
examples of resident cells in connective tissue
- fibroblasts: produce collagen & other fibres
- fibrocyte: cells that maintain fibres
- adipocyte: fat cells that store energy & cushioning
- mast cell: anti-inflammatory chemicals in response to allergens
- macrophage: initiates immune response & destroys pathogens
- blood cells: deliver oxygen and carbon dioxide around the body
what is connective tissue made of?
cells and extracellular matrix
loose connective tissue
- cushions and supports the epithelia, dermis, lamina propria, glands and ducts.
- supports vascular supply to epithelia and contain immune cells that protect against foreign antigens
- contains more cells and fewer fibres than dense connective tissue
where is loose connective tissue found?
- lamina propria beneath epithelial lining of the skin and digestive tract
- around glands and ducts
dense connective tissue
- contains more fibres and fewer cells
- tough / able to withstand more force
- irregular or regular
dense irregular connective tissue
- dermis (deep layer) of skin
- organ capsules
- submucosa layer of digestive tract
-> areas subject to twisting, pressure or friction that still need flexibility for embedded nerves and blood vessels
dense regular connective tissue
- ligaments
- tendons
-> areas that anchor other tissue and need to resist over-stretching
reticular connective tissue
- provides a 3D mesh-like scaffold
- supports soft organs
- typically found in bone marrow, liver, pancreas, adrenal glands & all lymphoid organs (except thymus)
-> flexible framework that supports cells with specific functions related to that organ
elastic connective tissue
- help structures like the aorta, larger arteries, and some ligaments ( spring back to original shape after being stretched)
-> structures that need to “rebound” to original shape after being stretched
specialized connective tissue
- bones
- cartilage
- adipose tissue
adipose tissue
- contains fat cells
- found below skin and around the organs
- stores energy
bone
- contains osteocytes
- provides structural support and protection
cartilage
- contains chondrocytes
- found at joints
- minimizes friction
fibroblasts
produce and secrete collagen that forms the extracellular matrix of loose (aerolar) connective tissue beneath the skin
ground substance
- allows diffusion of nutrients and chemicals throughout tissue
- anchors fibres and cells in tissue
- contributes to mechanical and structural support
- viscous and gel-like in structure
- has high water content
muscular system
- large group of contractible cells
- can contract and relax
- allow the body to move
three types of muscle tissue
- cardiac muscle
- smooth muscle
- skeletal muscle
cardiac muscle
- only found in the heart
- controls pumping of blood through the heart
smooth muscle
- found in the walls of hollow organs
- e.g. digestive sytsem, certain blood vessels
skeletal muscle
- most common
- controls all voluntary movement
- attached to bones
- contracts to facilitate movement
- contain bundles of long, multinucleated cells
- cells are striated
sarcomeres
contractile unit of muscles
cardiac muscle
- striated
- only found in the heart
- cells are long & branched
- cells are connected at intercalated discs
- contraction = involuntary, vigorous and rhythmic
- nuclei = cylindrical and centrally located
nervous tissue
- neurons -> nerve cells = functional unit of NS, send signals around the body
- glial cells -> support cells = protect and provide nutrients and immune functions to the neurons
neurons
excitable cells that produce action potentials when they are chemically or electrically stimulated
grey matter
cell bodies of neurons
white matter
myelinated axons
cerebrum
- largest part of the brain
- split into two hemispheres
cerebellum
- located at the base of the brain
- below cerebrum
- behind the brainstem
medulla
- connection between brainstem and spinal cord
- white matter
- brain stem
- composed of neuron axons
cortex
- grey matter
- outer layer of cerebrum
- composed of neuron cell bodies
astrocytes
- anchor neurons and capillaries together -> hold neurons close to nutrient supply
- barrier between neurons and capillaries -> help regulate chemical environment around neurons
microglia
- engulf microorganisms and dead neural tissue
- phagocytosis
ependymal cells
- line ventricles of brain and central canal of the spinal cord
- these cells are important for the production, absorption and circulation of cerebrospinal fluid
oligodendrocytes
- produce myelin sheath that wrap around and insulate nerve fibres
- speed up the conduction of electrical signals
what is a tract?
- bundle of axons (nerve fibres) that connects one part of the brain to another
- form the white matter of the CNS
- known as a nerve in the PNS
basket cells
make inhibitory synapses and control the overall potentials of target cells
stellate cells
- flattened cells
- around cell bodies of neurons
- regulate the chemical environment
- involved in repair
- liver-specific mesenchymal cells that play vital roles in liver physiology and fibrogenesis
- located in the space of Disse and maintain close interactions with sinusoidal endothelial cells and hepatic epithelial cells.
golgi cells
- pacemakers
- can impose specific temporal dynamics to granule cell responses
- located in the cerebellum
granule cell
- in the dorsal cochlear nucleus
- small neurons with two or three short dendrites that give rise to a few branches with expansions at the terminals
purkinje cell
- a unique type of neuron-specific to the cerebellar cortex
- massive, intricately branched, flat dendritic trees, giving them the ability to integrate large amounts of information and learn by remodeling their dendrites
what is the spinal cord?
- continuation of brainstem
- relays sensory and motor information between cerebral cortex, cerebellum, organs and limbs
- contains spinal meninges: dura mater, pia mater and arachnoid mater
pia mater
- thin, connective tissue
- tightly adhered to surface of spinal cord
arachnoid mater
- layer that looks like a spider-web
- provides protection and nutritional support to spinal cord
in which horn of the spinal cord do the cell bodies of somatic motor neurons lie?
anterior (ventral) horns
- axons exit via the ventral roots at each level of the spinal cord
- each axon has a target skeletal muscle
what runs through the central canal of the spinal cord?
cerebrospinal fluid
what kind of tissue is the extracellular matrix?
connective
- collagen
- reticular
- elastic
what are muscle tissues surrounded by?
fascia
what is fascia? where is it found?
- thin casing of connective tissue
- surrounds and holds every organ, blood vessel, bone, nerve fiber and muscle in place
function of fascia?
- provides structure and support throughout your body
- hold muscles together -> allows them to contract and stretch
- provides a smooth surface for your muscles, joints and organs to slide against each other without creating any friction or tears
