suger wrap up Flashcards
Layers of the skin
Epidermis
Dermis
Subcutaneous fatty tissue
Layers of the epidermis
Stratum corneum Stratum lucidum Stratum granulosum Stratum spinosum Stratum basale
Features of the stratum corneum/lucidum
Annulated keratinocytes.
Corneodesmosomes hold corneocytes together.
Features of the stratum granulosum
Contains granules:
- keratohyaline granules
- lysosomal enzyme
- odland bodies (lipids - prevent water loss)
Features of the stratum spinosum
‘prickle layer’
5-10 layers
plump polygonal keratinocytes
contains Langerhans and Merkels cells
Features of the stratum basale
single layer
Basal epithelial cells and melanocytes
Columnar and perpendicular to basement membrane.
Mitotically active.
How is the epidermis separated from the dermis?
By a ridges basement membrane which forms ‘rete ridges’
Describe the papillary dermis
Closer to the basement membrane.
Loose meshwork, poorly organised type 3 collagen and elastic fibres
Abundant in small blood vessels, fibroblasts and ground substance
Describe the reticular dermis
Thick bundles of well organised type 1 collagen with thick elastic fibres
Also contains vessels and ground substance, plus macrophages and mast cells
what is the subcutaneous layer of the skin composed of?
functions?
Lobules of mature adipocytes with intervening fibrous tissue septae.
Functions: insulation, food store, shock absorber
Compare Pacinian and Meissner’s corpuscle in relation to:
- size
- location
- function
- appearance
Pacinian: large deep dermis and subcutis coarse touch, vibration, tension onion appearance Meissner's: small dermal papillae light touch spiral appearance
Describe the protective function of the skin
Strong physical barrier protects from trauma, dehydration and invasion by pathogens, UV light protection via melanin
Describe the sensory function of the skin
Somatic sensory receptors allow transmission of signals regarding pain, temperature and light touch
Describe the function of the skin in temperature regulation
Regulation of blood flow, erection of hairs, release of sweat
Describe the immune function of the skin
Specialised cells (e.g. Langerhans, phagocytes destroy microorganisms and interact with rest of immune system. Acidic environment.
How is the skin adapted to allow movement and growth?
elastic and recoil properties
Role of the skin in excretion
Waste products removed from surface of the skin e.g. water, urea, ammonia, uric acid – regulated by sweat composition
Endocrine function of the skin
synthesis of vitamin D from sunlight
why does the R kidney lie lower than the left?
liver is on the R - has to accomodate
At which vertebral level do the kidneys lie at?
T12-L3
ARe the renal arteries above or below the coeliac trunk?
Below - near sup. mesenteric
3 coverings of the kidneys
Gerota’s fascia, perinephric fat, renal capsule
How many arteries supply adrenals?
3:
aorta, renal artery, inferior phrenic artery
Where does the urogenital sinus originate? what will it eventually form?
From cloaca.
Forms bladder and urethra.
Where does the ureteric bud originate? What does it eventually form?
From mesonephric duct.
Forms ureters, calices and collecting ducts.
3 stages of kidney development
- pronephros
- mesonephros
- metanephros
which embryological kidney forms the permanent kidney? when does it start functioning?
Metanephros
Functions at 12 weeks
Which stage of developing kidney gives rise to the mesonephric duct (Wolffian duct)?
When does this kidney form disappear?
mesonephros
disappears 2nd month
what does the Wolffian duct go on to form?
vas deferens, epididymis, seminal vesicles, ejaculatory duct
what week does sex differentiation occur?
week 7
4 functions of kidney
water/acid-base/ion balance
waste removal
gluconeogenesis
hormone production
How much of the cardiac output is to kidneys?
20%
Normal GFR
100ml/min
Normal rate of urine production
1ml/min
Sodium channel present on the ascending limb of the nephron
NKCC2
Limb is impermeable to water, sodium actively pumped out
Describe sodium reabsorption in the ascending limb
NKCC2 channels (reabsorption of sodium, K+ and 2Cl-)
Describe sodium reabsorption in the PCT
sodium channels exchange sodium for H+ (most reabsorption occurs here) and water follows passively
Describe sodium reabsorption in the DCT
NCC channels transport Na+ and Cl-
Describe sodium reabsorption in the collecting duct
regulation of ion channels
ENaC (epithelial sodium) channels transport sodium in from tubular fluid. Water follows passively. K+ enters tubular fluid from blood (exchanged with Na+ by Na/K ATPase).
Aldosterone regulates ENaC and Na+/K+ channels.
Describe the permeability of the descending limb of the nephron
Impermeable to sodium.
Water out via aquaporins.
What happens to hypertonicity as you move further into the medulla?
Increases
What detects decrease in renal perfusion?
- renal sympathetic nerves
- intrarenal baroreceptors in the afferent arteriole
- cells of the macula dense
In response to a decrease in renal perfusion, which cells will produce Renin?
Juxtaglomerular cells of the afferent arteriole of the kidney
(juxtaglomerular apparatus)
What produces angiotensinogen?
the liver
what does angiotensinogen do?
Inactive, circulates in blood and is converted by renin to angiotensin 1
What produces ACE?
lungs - surface of pulmonary (and renal) epithelium
What does ACE do?
Converts angiotensin 1 to angiotensin 2 in the blood vessels
Describe the actions of angiotensin 2
what do all of these factors cause?
- increases sympathetic activity
- increases tubular Na+Cl- reabsorption, K+ excretion and H2O retention
- causes secretion of aldosterone from adrenal gland cortex
- increases arteriolar vasoconstriction
- increases ADH secretion from the posterior pituitary gland, leading to H2O absorption in the collecting duct
EFFECT: increased effective circulating volume (increased blood pressure)
What does aldosterone producted by the kidney cortex in response to angiotensin 2 cause?
How does it work?
Increases tubular Na+Cl- reabsorption, K+ excretion and H2O retention.
It does this by: binding to a cytoplasmic receptor which is transported to the nucleus.
This increases action of ENaC and Na/K ATPase channels.
What triggers ADH release?
How is this detected?
How does ADH work?
Triggers: increased plasma osmolality and reduced blood volume
Detected by: hypothalamic osmoreceptors
How does it work: aquaporin insertion in collecting duct
Continence and micturition - nerve supply
Sympathetic: hypogastric nerve
Parasympathetic: pelvic nerve
VoluntaryL pudendal nerve
(S2,3,4 keeps the piss off the floor…)
Storage of urine:
- control?
- muscles/sphincter
- nerve
- Sympathetic
- Internal urethra sphincter contracted
- detrusor muscle relaxed
- hypogastric nerve T10-L2
Voiding:
- control
- sequence of events
- nerves
- Parasympathetic
- Internal urethral sphincter relaxes
- Bladder neck funnels
- Detrusor contracts
- Internal urethral sphincter relaxes
- Pelvic nerve, S3-5 from sacral plexus
AND
voluntary control:
pudendal nerve controls external urethral sphincter
Layers of the bladder wall
- Urothelium (also called transitional epithelium)
- Lamina propria
- Muscularis detrusor
- Adventitia
Arterial supply of the thyroid
Superior thyroid artery (branch of external carotid)
Inferior thyroid artery (branch of subclavian)
Venous drainage of the thyroid - why is this significant?
Superior and middle veins, drain into internal jugular.
Inferior vein drains into brachiocephalic vein.
Significant for hormone release.
2 proteins which bind thyroxine in the blood
Albumin and thyroxine binding globulin
How is T4/T3 excreted?
Deiodinated by liver and kidneys
effects of thyroxine
- increases oxygen consumption at tissues
- increased metabolism
- excess causes muscle breakdown
- brain maturation
- growth
Thyroid histology:
- C cells
- follicular cells
- follicle
- C cells: produce calcitonin, are alongside the follicles
- follicular cells: form a cuboidal epithelium
- follicle: hollow spheres containing inert thyroxine
Brief steps of spermatogenesis
- Spermatogonia forms a spermatocyte
- Meiosis 1: the spermatocyte forms 2 spermatocytes
- Meiosis 2: 2 spermatocytes form 4 spermatids
- Spermiogenesis: spermatids forms spermatozoa which adapts to move: sprouts tail, discards excess cytoplasm, acrosome forms
Factors affecting puberty
- nutrition
- genetic
- exercise
- socio-cultural
- hormones
Hormonal changes in puberty
- ↑ amplitude of hypothalamic endocrine secretions
- ↑ levels of FSH, LH and sex steroids
- ↑ growth hormone
Centrally driven and depends on hypothalamic-pituitary-gonadal (H-P-G) axis
OOgenesis
meiosis 1 and 2
Meiosis 1: Begins in uetero, before 12 weeks Homologous recombination and crossover > variation 46 XX > 23X + 23X Arrested in metaphase 1 until puberty. Meiosis 2: LH surge at puberty > resumation Equatorial division 23X > 23X + 23X Arrested in metaphase 2 until fertilisation.
Endometrial phases:
describe the proliferative phase
oestrogen stimulation causes straight glands so show mitotic activity and become tortuous glands.
No luminal secretions.
Stromal cells: spindled, compact, show mitotic activity.
Endometrial phases: describe the secretory phase - early - mid - late
EARLY: sub-nuclear vacuoles MID: Vacuoles above and below nucleus Intraluminal secretions (pink) Rounded glands Stromal oedema LATE: Spiral arterioles in stroma Elongated, saw-tooth glands with ↑ luminal secretions
Describe pre-implantation:
from pertilisation to hatching
- Fertilisation – day 1
Spermatozoon penetrates zona pellucida surrounding oocyte and gametes fuse to form zygote - Cleavage – day 2-3
Ooplasm divides into two equal halves and successive cleavages > ↑ cell no. - Compaction – day 4
Cells flatten and tight junctions form, max. intracellular contacts - Cavitation and differentiation – day 5
Fluid filled cavity expands to form blastocyst - Expansion – day 5-6
Cavity expands further and diameter of blastocyst ↑, zona pellucida thins - Hatching – day 6+
Blastocyst expansion + enzymes > hatching of embryo from zona pellucida
Necessary for implantation…
Describe the implantation of the blastocyst, startinf with apposition
Apposition – starts ~ 9 days after fertilisation
Hatched blastocyst orientates via embryonic pole and synchronises with receptive endometrium (day 19-22 of cycle)
Attachment
Endometrial epithelial cells and trophoblastic cells express integrins which connect with one another
Differentiation of trophoblast
Trophoblast > cytotrophoblast + syncitiotrophoblast (erodes endometrial blood vessels)
Invasion
Enzymatic degradation of basal lamina
Decidual reaction
Differentiation of stromal cells adjacent to blastocyst
Maternal recognition
Secretion of interleukin-2 prevents antigenic rejection of embryo
Skin changes during prgnancy
Linea nigra: dark central line on abdo
Striae gravidarum: strech marks in lumbar/lower abdo regions
Darkened areolar of breast
Spinal changes in pregnancy
increased lumbar lordosis
stages of labour
- latent phase: little cervical dilation
- active phases - organised uterine contractions and dilation:
stronger, higher frequency contractions
full dilatation –> foetal expulsion
placental expulsion - post partum phase
