Histology Flashcards
describe the three main components of connective tissue
ground substance
- semi solid clear gel
- made up of glycoproteins and glycosaminoglycans like hyaluronic acid
- water binding ability due to proteoglycans and glycosaminoglycans
- gives tissue volume
fibres
- collagen, elastin and reticular fibres.
- collagen is very strong, elastin is stretchy and reticular makes a network.
cells
- blasts and cysts to make up the connective tissue components.
- fibroblasts, osteoblasts, chondrocytes etc
- there are also immune cells in some, but not in cartilage tendons or ligaments
describe the criteria used to classify connective tissue
there are three classifications: proper, supporting and fluid.
proper
- loose, dense, or elastic
- dense regular and dense irregular
- dense regular is strong in one direction due to fibre arrangment, found in tendons and ligaments
- dense irregular is strong in many directions, like dermis of the skin.
- elastic is dense too, found in arteries.
- loose is areolar, adipose and reticular
- areolar holds together the GIT, anchors organs of the body
- reticular is found in spleen and lymphatics
- adipose is fat, helps with energy storage and shock absorption.
supporting
- bone and cartilage
- cartilage can be hyaline, elastic and fibrocartilage
- hyaline is joints
- elastic is epiglottis and ear
- fibrocartilage is vertebrae and meniscus of the knee
fluid
- blood
- important for transport and immunity
describe some connective tissue disorders with oral manifestations
scurvy
- lack of vitamin c affects collagen synthesis
- glycine, proline and hydroxyproline form collagen structure, and vitamin C is a co factor for forming this
- collagen supports blood vessels, tendons and skin. they are fragile without it
- causes teeth to become loose, haemorrhages and death
systemic lupus erythematosis
- autoantibodies attack host tissues like skin, bone, tendon and kidneys
- cause dryness, soreness, buccal and palatal lesions in the mouth
sjogrens
- autoantibodies affect glands producing tears and saliva
- dry eyes and mouth, make mouth susceptible to infection and caries
describe the relationship between the structure and function of connective tissues
all connective tissues have different structural arrangements for their function
tendons
- dense regular, helps tendon transfer the force of muscle contraction to bone
- connect muscle to bone
describe features common to all epithelial tissues
structurally:
- continous sheets of cells
- tightly bound together
- polarised
functionally:
- cover and line surfaces
- form a barrier
classify epithelial tissues
structure differs by shape of cell, number of layers, and apical specialisations
squamous are flat, cuboidal are square, and columnar are long, with nuclei at the basement membrane.
apical specialisations include cilia, keratin and microvilli
number of layers are either single, simple, or many, stratified, or single with nuclei at different levels, pseudostratified
list the functions of different epithelial classifications
simple squamous - passive diffusion, lungs and capillaries
simple cuboidal - small ducts involved in absorption or secretion, renal tubules and salivary glands
simple columnar - absorption - small intestine
cililated simple columnar - ovum from ovary to uterus, female reproductive tract
pseudostratified columnar ciliated - respiratory epithelium
stratified cuboidal - secretory - some glands and ducts
stratified columnar - secretory and protective - male urethra and glands
stratified squamous - protective, skin and oral mucosa
transitional - expansion and stretch, bladder only
disorders of epithelium in oral environment
ulcerations
- break in the continuity of epithelium
- can be infectious or not
oral squamous carcinoma
- dysplastic epithelium
- invades adjacent tissue
describe the organisation of skeletal muscle at the tissue level
composed of skeletal muscle cells
- elongated, cylindrical fibres with multiple peripherally located nuclei
- main type in skeletal muscle
individual muscles are organs, composed of muscle tissue, connective and nervous tissues.
each fibre is wrapped by endomysium. each fasicle of fibres is wrapped by perimysium, and each group of fasciles is wrapped by epimysium
describe the components of skeletal muscle fibres involved in contraction by sliding filament mechanism
myofibrils are arrangement to show a striated appearance
myofibrils are composed of myosin (dark bands) and actin (light bands), and the actin is bisected by z lines
it is the z lines that divide each myofibril into contractile units called sarcomeres
each sarcomere contains an A band, H band , M line, and a bisected I band.
A band - the entire length of the myosin filament
H band - the length of myosin not overlapping actin
M line - bisects the myosin
I band - the length of actin not overlapping the myosin
identify the components of the neuromuscular junction and the special adaptations of muscle fibres that support synchronous contraction of sarcomeres
skeletal muscle is innervated by somatic motor neurons
a motor unit is the single motor neuron and the muscle fibres it innervates
neuronal action potentials are converted into acetylcholine at the NMJ, which is detected by receptors on muscle fibres to stimulate action potential and contraction. this is excitation contraction coupling
excitation contraction coupling mechanism in detail:
- sarcolemma is the membrane, invaginates into the sarcoplasm (cytoplasm) to form t tubules that are continuous with the extracellular sapce
- sarcoplasmic reticulum is smooth endoplasmic reticulum containing calcium
- sarcolemma and SR support sarcomere contraction
identify the structural and functional differences between skeletal muscle and cardiac muscle cells
cardiac is found only in the heart to create autonomic contraction
elongated, branched cylindrical cells with one or two centrally located nuclei.
skeletal striated muscle has multiple, peripherally located nuclei.
both are striated.
cardiac muscle makes up the myocardium of the heart, the middle layer between the pericardium and the endocardium.
reticular connective tissue supports the cardiac muscle.
both cardiac and skeletal muscle have the same sarcomere arrangement, with t tubules and a sarcoplasmic reticulum. they both have a lot of mitochondria, glycogen and lipids. both contract by sliding filament mechanism.
however, cardiac is autonomic, the SR slowly leaks the calcium ions, and has intercalated discs to allow cardiac muscle cells to function as synctium.
skeletal contracts via motor neurons
cardiac contracts via sino atrial node and slow release of calcium ions. it is modulated by autonomic nervous system and hormones
identify the structural and functional differences between skeletal muscle and smooth muscle
smooth is elongated, spindle shaped cells
one nuclei, centrally located
no sarcomeres, which means there is no striation
comprises the gastrointestinal tract with inner circular and outer longitudinal
has actin and myosin like the skeletal, but arranged in criss cross lattice. when contracted it becomes shortened and globular.
skeletal is voluntary, smooth is involuntary. smooth is also non striated.
describe the main histological components of cartilage
ground substance with chondroitin sulphate
fibres like collagen and elastin
cells like chondroblasts and chondrocytes
hyaline cartilage contains collagen and ground substance, found in articulating bones
elastic cartilage is flexible and avascular, has elastic fibres concentrated around lacunae and collagen fibres
fibrocartilage is durable and tough, does not have much ground substance and is composed of dense irregular collagen and chondrocytes. found in vertebrae.
describe the histological components of cortical bone
compact bone, surrounded by periosteum, which is composed of an outer fibrous layer and an inner osteogenic layer.
layers of bone tissue are referred to as lamellae, and are arranged concentrically.
central canals run through the centre of each osteon to house blood vessels, nerves and lymphatics.
there is circumferrential lamellae that surrounds the entire cortical bone parallel to the periosteum.
