ANAT Y1 S1: Epithelium + Skin Flashcards
1
Q
what is epithelium and give some examples
A
- tissue that forms the internal and external surfaces of the body > found by palpation and biopsy
- e.g. skin, GI tract etc.
2
Q
endothelium
A
epithelium of the CV system (simple squamous)
3
Q
functions of epithelium
A
- protection: skin
- absorption: small intestine, kidney, capillaries
- secretion: small intestine, trachea
- transport: kidney
- sensory reception: epidermis
4
Q
5 characteristics of epithelium
A
- tightly packed: little space between cells and strong attachments b/n cells (tight junctions)
- oriented/polarised: apical and basal surfaces are different
- sit on a basal lamina (basement membrane) and exposed area is the apical surface
- avascular > otherwise susceptible to abrasions, instead gets nutrients from underlying connective tissue
- fast rate of regeneration
5
Q
2 ways to categorise epithelia
A
- cell layers: simple (1 cell thick), stratified (multilayered)
- shape of most superficial cell: squamous (squashed/flat), cuboidal (cube), columnar
6
Q
where to find all types of simple epithelium
A
- simple squamous: diffusion and filtration b/c thin e.g. endothelium, alveoli
- simple cuboidal: secretion and absorption e.g. salivary glands and renal tubules
- simple columnar: absorption and mucus secretion e.g. lining stomach + intestines, bronchi, uterus, fallopian tubes
7
Q
where to find all types of stratified epithelium
A
- stratified squamous: protects against abrasion e.g. mouth, tongue, oesophagus, vagina, skin (keratinised)
- stratified cuboidal: protective tissue e.g. sweat glands, mammary glands, salivary glands
- stratified columnar: protects and secretes e.g. male urethra
8
Q
where to find pseudostratified epithelium
A
- trachea, bronchi, epididymis, vas deferens
- pseudo because technically every cell is connected to the basement membrane but looks multilayered b/c nuclei are seen at diff levels
9
Q
where to find transitional epithelium (stratified)
A
- ureter, bladder, urethra
- can change shape (thinner or thicker)
10
Q
apical specialisations
A
- microvilli: extensions of apical cell membrane w/ large SA for absorption, containing actin filaments
- cilia: elongated motile structures that beat in a synchronised manner: made of microtubules in a 9+2 structure e.g. ovaries, respiratory tract
11
Q
lateral specialisations from most apical to basal
A
- tight junction (zonula occludens)
- belt desmosome (zonula adherens)
- spot desmosome (macula adherens)
- gap junctions (nexus)
- hemidesmosome (basal)
12
Q
function of tight junction (zonula occludens)
A
- prevents flow of material between cells, occluding (blocking) intercellular space
13
Q
belt desmosome (zonula adherens)
A
- actin filaments which provide adhesion between adjacent cells
14
Q
(spot) desmosomes (macula adherens)
A
small, plaque-like thickenings on membranes of adjacent cells made of INTERMEDIATE FILAMENTS for adhesion
15
Q
function of gap junctions (nexus)
A
- ion flow (electrical coupling) between cells via connexons
- important in cardiac & smooth muscle so it can contract at the same time with one signal
16
Q
hemidesmosome
A
attaches epithelial cells to basal membrane
17
Q
structure and function of basal lamina
A
- S = collagen IV, proteoglycans, glycoproteins
- F = epithelial cell orientation and adhesion
- normal epithelial cells do not cross basal lamina but cancer cells can
18
Q
compare endocrine vs exocrine glands with relation to epithelium
A
- exocrine: retain connection w/ surface epithelium ie secrete substances onto epithelium e.g. sebaceous, sudoriferous, mucus
- endocrine: lose attachment w/ surface epithelium ie secrete substances into the blood
19
Q
meissner’s corpuscle
A
- ENCAPSULATE nerves in dermal papillae
- barrel-shaped w/ capsule on top
- abundant in fingertips
- fine touch + sensation
20
Q
pacinian corpuscle
A
- looks like an onion
- ENCAPSULATED sensory nerve endings in deep dermis
- deep pressure + vibration (type of mechanoreceptor)
21
Q
myoepithelial cells
A
- modified smooth muscle cells
- help to facilitate secretion surrounding sweat + sebaceous glands
- mammary versions are ‘natural’ tumour suppressors b/c they prevent epithelial cells penetrating through the basement membrane
22
Q
structure of the dermis
A
- papillae (invaginations - loose CT)
- reticular layer underneath (dense irregular CT - pink stuff is collagen and white stuff is ground substance)
23
Q
structure of epidermis
A
- Langerhans cells (dendritic cells)
- thin skin epidermis replaced every few weeks (quicker than thick skin)
- Come Let’s Get Sun Burnt
- stratum corneum (hundreds of layers of keratin)
- stratum lucidum (only thick skin - lose nucleus and organelles)
- stratum granulosum: releases keratohyalin which forms keratin
- stratum spinosum: many desmosomes
- stratum basale/ germinativum (melanocytes, single epithelium layer on basement membrane)
24
Q
function of melanocytes
A
- secrete melanin to protect deeper cells of the epidermis and DNA from UV radiation
- dead keratinocytes don’t need it
- can give rise to melanoma
25
Q
structure and function of sweat glands
A
- S = simple coiled tubular glands
- F = secretes water, NaCl, urea etc
- eccrine: open to skin, smaller, more numerous, thermoregulation
- apocrine: open to hair, larger, less numerous, acted upon by bacteria > produce odour
26
Q
structure and function of sebaceous glands
A
- S = fat, juicy glands associated with a hair follicle and surrounded by myoepithelial cells (only in hairy/thin skin)
- F = cells fill with lipids and burst to secrete sebum (holocrine excretion)
27
Q
thin/thick/hairy/non-hairy skin
A
- thin = hairy
- thick = non-hairy (e.g. palms and soles) - stratum lucidum only on thick skin
