Tissues Flashcards
describe the stages required for tissue preparation for histology
collecting - depends on where the tissue is, skin punch biopsy, organ needle biopsy
fixation - to preserve tissues as they are invivo, done using chemical formaldehyde stops processes
dehydration - must be put in wax which is incompatible with water - series of increasing alcohol conc. to remove
embedding - placed in a wax block of paraffin wax
sectioning - 7um thick sections cut using microtome, mounted on to glass slide
staining - to see certain structures of the cell
what stains are used in histology
H&E - stains nuclei purple and cytoplasm pink
PAS - stains complex carbohydrates pink
Masson’s trichrome - nuclei blue, collagen green and muscle red
what is immunohistochemistry
using antigen to antibody binding to see a specific protein, antigen bound to fluorescence
what are the 2 main types of epithelium
glandular and surface
name 4 roles of epithelium
protection - many layers protecting underlying tissue, secretion - secreting sweat when temperature too high, absorption - many creams or topical medication, diffusion - in lungs, diffusion of gases
where can simple squamous epithelium be found
in the alveoli of the lungs, for diffusion
where can simple cuboidal epithelium be found
in several glands, kidney or salivary, for secretion
where can simple columnar epithelium be found
can either be ciliated or non-ciliated - nonciliated in gastrointestinal tract role in absorption, ciliated in female fallopian tubes, cilia waft egg along tube
where can pseudostratified epithelium be found
most commonly, columnar found in respiratory tract with cilia
where can stratified squamous epithelium be found
surface epithelium, keratinised in skin and masticatory mucosa of the mouth, non-keratinised in lining mucosa
where can transitional epithelium be found
in bladder, transitional to accommodate the stretching of the bladder
what components make up the connective tissue
ground substance, fibres and cells
what is ground substance
gel-like, weak substance to allow transfer between cells made of glycoproteins or hyaluronic acid
what fibres can be found in connective tissue
collagen - several different types found in different areas, provides mechanical strength, elastin - to provide elasticity in areas eg the lungs
what different cell types can be found in CT
blasts - producing tissue, cytes - maintaining and clasts breaking it down. also several blood vessels as is highly vascularised and immune cells
what are the main types of connective tissue
connective tissue proper - loose or dense, skeletal - bone or cartilage, fluid - blood or lymph
what are the types of loose connective tissue
reticular, areolar and adipose
how can reticular loose CT be classified and where can it be found
characterised by black reticular fibres - type 3 collagen, provides framework for highly cellular structures, found in liver, lymph nodes and spleen
how can areolar loose CT be classified and where can it be found
high volume of ground substance, found in submucosa and under skin epithelium
how can adipose loose CT be classified and where can it be found
adipocytes in the ground substance, either found within tissue - subcutaneous - or on its own mamillary tissue
what are the types of dense connective tissue
regular, irregular and elastin
how is regular dense CT characterised and where can it be found
characterised by collagen fibres in the one direction, providing tensile strength in the one direction, found in ligaments and tendons
how is irregular dense CT characterised and where can it be found
characterised by collagen fibres in multiple directions, providing tensile strength in many ways, found in subcutaneous, connective tissue surrounding organs (e.g. pericardium)
how is elastin CT characterised and where can it be found
characterised by elastin fibres, providing elasticity, around major blood vessels, lungs, bladder
what is scurvy
deficient in vitamin C, unable to make collagen fibres effectively, results in connective tissue lacking strength, tooth loss
in bone, how much percentage of the ECM becomes mineralised with hydroxyapatite
70%
how is bone mineralised
osteoblasts deposit collagen fibres and vesicles - osteoid, over time these vesicles become mineralised to hydroxyapatite crystals
what is the periosteum composed of
2 layers - fibrous layer of dense irregular CT, blood vessels and lymphatics, cellular layer of osteogenic cells and osteoblasts
how is cortical bone arranged
in osteons, which contains bone in layers of lamellae with a central canal of blood vessels, lymphatics and nerves,
how are osteons produced
osteoclasts break down bone in the centre to make a central canal, osteoblasts around the outside of each layer lay down new bone, when the osteoblasts become trap in the bone they are known as osteocytes
where can traberculae bone be found
ends of long bones, in epiphysis
how is traberculae bone arranged
arranged in lamellae in rods to form a lattice shape
where can endosteum be found
surrounding the central canal, around the rods of the traberculae bone
what is different about cartilage compared to other CT
it is avascular
what are the cells of cartilage
chondroblasts laying down cartilage, chondrocytes - when blasts get trapped in lacunae
what is the 3 types of cartilage
hyaline cartilage, fibrocartilage, elastic cartilage
where is hyaline cartilage found
around the ends of bones, preventing friction at joints
what is hyaline cartilage lacking
perichondrium, means it lacks the ability to repair, once lost it cannot be repaired
where is fibrocartilage found
abundant cartilage fibres so more strength, surround joint capsule and vertebral disc
where is elastic cartilage found
more elastin fibres, epiglottis, larynx and external ear
what is osteomalacia and what is it commonly known as in children
lack of vitamin D, results in weaker bones due to lack of absorption of calcium, known as rickets in children as weight bearing bones more effected
what are the different types of endocrine secretion and give an example of each
chronic - always secreted at same levels, no stimulus required, thyroid hormone
acute - released in response to stimulus, amount secreted dependant on level of stimulation, adrenaline
episodic - released in response to stimulus, same amount released regardless of activation, insulin
what regulates endocrine secretions
other molecules - glucose levels - humoral
neurones - noradrenaline causes adrenaline release
other hormones - hypothalamus to pituitary
what are the two structures an exocrine gland may have
tubule or acinus
what is meant by a compound structure of an exocrine gland
when many branches of tubules or acinars come together to form a duct
what are the different methods of secretion of exocrine glands
merocrine - packaged into vesicle, contents released
apocrine - packaged into vesicle, vesicle then pinched off holocrine - whole cell pinched away and released
what types of secretions are released from exocrine glands
mucous, serous or mixed
how do mucous secretions appear histologically
appear pale in colour with nuclei around periphery of cell
how do serous secretion appear histologically
appear pink in colour with central nuclei
why can cancer of the pancreas not be removed surgically
it releases enzymes in surgery to cause degradation of the pancreas structure resulting in death of the organ
describe 4 functions of the skin
sensation, absorption, protection and thermoregulation
what are the layers of epidermis of the skin
stratum basale, stratum spinosum, stratum granulosum, stratum corneum
what is the difference between thick and thin skin
thick skin has an extra layer - stratum lucidum, can produce waxy oils, also has a thicker stratum corneum
what cells can be found in skin, other than epithelial cells
merkel cells - nerve receptors, melanocytes for skin pigmentation, langerhans cells detecting infection
what layers make up the dermis
papillary layer and reticular layer
where is the papillary layer of the dermis found and what is it composed of
found in rete pegs, underlying rete ridges, composed of loose areolar connective tissue, blood vessels and nerves
where is the reticular layer of the dermis and what is it composed of
found under the papillary layer, composed of dense irregular connective tissue with collagen and elastin fibres
what is psoriasis
a skin condition in which the cells are dividing too quickly so the cycle is only 7 days, the cells at the top superficial layer are not dead and are pron to bleeding
what is pemphigus
when the desmosomes attaching adjacent cells are attacked, the cells break away from one another allowing fluid between them, results in blisters, can occur in the oral cavity
how is cystic fibrosis characterised
goblet cells over secreting mucous, blocks duct and airways
describe the general structure of a skeletal muscle
one muscle fibre covered by endomyosium, a bundle of fibres held together in a fasicle by perimyosium, and then several fasicles form the muscle, covered in epimyosium
what myofilaments make up the sacromere
actin and myosin
how are the filaments arranged in the sacromere (in terms of bands)
Z line between each sacromere, M line in the centre of the sacromere, H band where myosin only filament, I band with actin only filaments and the A band where actin and myosin filaments overlap
what is the sacrolemma
membrane of the sacromere, contains invaginations called T-tubules, containing receptors for acetylcholine
what is the sacroplasmic reticulum
similar to endoplasmic reticulum but contains calcium ions
what are the layers of the heart muscle
endocardium, myocardium, pericardium
what are the similarities between cardiac and skeletal muscle
both have sacrolemma, sacroplasmic reticulum, sacromere, contract by sliding filaments
how do skeletal and cardiac muscle differ
cardiac has intercalated discs - gap junctions to allow electrical transmission from one cell to another, cardiac has a constant leakage of calcium, cardiac can be altered by hormones or nerves, cardiac is involuntary
what is the shape of the smooth muscle
spindle shaped when relaxed, globular when contracted. with one central nuclei
how are myofilaments arranged in smooth muscle
in a criss-cross lattice shaped, attached on one end to the membrane by focal densities - contraction brings the membrane closer together
