Physiology Flashcards
What cell type releases renin?
Juxtaglomerular cells in kidney blood vessels (afferent arteriole)
What type of cells are juxtaglomerular cells?
Specialised smooth muscle cells
What are the triggers for renin release from JG cells?
low blood pressure, sympathetic stimulation, low salt (via macula densa)
Where are macula densa cells found and what do they respond to?
found in DCT, respond to low salt (= low BP)
What messengers do macula densa cells secrete?
prostaglandins
what secretes angiotensinogen?
liver cells
how does angiotensinogen form angiontensin II?
renin first comes into contact in the blood, cleaves it into angiotensin 1 ACE in endothelial cells converts angiotensin 1 -> angiotensin 2
What does angiotensin 2 act upon?
- smooth muscle cells (vasoconstriction) 2. Kidney (increased water reabsorption) 3. pituitary gland (ADH) 4. adrenal gland (aldosterone)
Where are baroreceptors located?
aortic arch, carotid sinus
How does ADH act?
acts on the collecting duct (impermeable) by causing the insertion of aquaporins vasoconstriction
How does aldosterone act in the kidney?
causes increased Na+ reabsorption, which also draws back in water
Where in the adrenal gland is aldosterone made?
cortex
What are the triggers for aldosterone production?
- angiotensin 2 2. high K+ in blood
where in the nephron does aldosterone act?
late DCT + collecting duct
what cell types are found in the collecting duct?
principal cells intercalated cells
what does aldosterone do in principal cells?
- increased action of Na+/K+ ATPase on basolateral surface 2. K+ channels added to apical surface (passive) 3. Na+ channels onto apical membrane
folic acid
found in leafy plants, yeast, liver essential for DNA formation + cell division (thymine synthesis)
Vitamin B12 absorption
absorbed by intrinsic factor (parietal cells) B12 bound to intrinsic factor binds to receptors in the ileum - endocytosis
blood formation hormone
erythropoieitin secreted by kidneys stimulates division of erythrocyte progenitor cells in marrow
erythropoieitin stimulant
stimulated by decreased O2, testosterone
Functions of kidneys
- regulate water concentration
- excrete metabolic waste + foreign chemicals
- gluconeogenesis
- endocrine (erythropoieitin, 1,25 dihydroxy vit. D) + renin
how much of the blood plasma filters into the bowmans capsule?
20%
filtration barrier in glomerulus
- capillary endothelium (1 cell thick)
- basement membrane
- epithelia lining of bowmans capsule (podocytes)
mesangial cells
specialised smooth muscle surrounding capillary loops in glomerulus
types of nephron
juxtaglomedullary - 15%
- deep, vasa recta
- form osmotic gradient
cortical - 85%
- loops not deep
- only reabsorption + secretion
Net glomerular filtration pressure
PGC-PBS-πGC
glomerular capillary hydrostatic P
Bowmans space fluid P
osmotic force due to plasma fluid
GFR
volume of fluid filtered from glomerulus into BS per unit time
determined by net filtration pressure, membrane permeability, SA
GFR proportional to membrane permeability + SA
What is normal GFR
125ml/min = 180L per day
all plasma (3L) filtered 60X per day
para/mesonephric duct
Mesonephric - male
paramesonephric - female
cloaca
anorectal canal (dorsal) + urogenital sinus (ventral)
mullerian/wolffian ducts
mullerian duct - female reproductive tract (fallopian tubes, uterus, cervix, superior 1/3 vagina)
wolffian duct - male internal genitalia (SREEVES)
urogenital ridge forms:
- pronephros (regresses)
- mesenephros (mesonephric duct)
- metanephros (kidney (ureteric bulge/metanephric blastema))
Male development
SRY gene, gonads form testis
leydig cells - testosterone - mesonephric duct growth
sertoli cells - AMH/MIS - paramesonephric duct regression
testis descend with gubernaculum
male derivatives
ureteric bud - ureter, calyces, collecting ducts
mesonephric ducts - SREEVES, trigone
urogenital sinus - bladder, prostate, bulbourethral gland, urethra
Female development
No SRY gene - gonads form ovary
no testosterone - mesonephric duct regression
no AMH/MIS - paramesonephric duct grows
Female derivatives
ureteric bud - ureter, calyces, collecting ducts
mesonephric ducts - trigone
paramesonephric ducts - oviducts, uterus, upper 1/3 vagina
urogenital sinus - bladder, bulbourethral glands, urethra, lower 2/3 vagina
pregnancy hormones
- progesterone
- oestrogen
- hCG
- Prolactin
- oxytocin
- relaxin
What secretes hCG?
trophoblast - forms fetal placenta
Stimulates further oestrogen+ progesterone secretion
(pregnancy test hormone)
what does the surrounding tissue in an ovarian follicle become?
corpus luteum - corpus albicans
What does the corpus luteum secrete?
Progesterone + oestrogen - prevent other follicles from maturing
Maternal changes in pregnancy
- increased HR + volume, decreased haematocrit, decreased BP (vasodilation)
- hypotension - pressure on IVC when lying
- urinary frequency increased
- increased tidal volume, costal ligaments relaxed (bucket handle)
- decreased CO2 - respiratory alkalosis
- breast development/milk production - oestrogen/prolactin
- increased blood clotting (increased fibrinogen)
MSH
melanocyte hormone - stimulates darkening of areola + linea nigra
menstrual cycle phases
- follicular (day 1-14) - includes menstrual + proliferative phases
- luteal (day 14-28) - includes secretory phase
Follicular phase
- GnRH release - stimulates FSH + LH release
- LH - theca cells - release androgens into follicle
- FSH - granulosa cells - enzyme to form estradiol from androgens
- increased estrogen - decreased FSH, most follicles die
- then increased estrogen - increased FSH - surge - rupture of oocyte
*
What releases GnRH and FSH/LH
GnRH - hypothalamus
FSH/LH - anterior pituitary
luteal phase
- corpus luteum continues estrogen production
- decreased LH - granulosa cells make more progesterone
- decreases LH/FSH (-ve feedback)
- inhibin also released
menstrual, proliferative, secretory phases
- menstrual - old endometrial lining shed (period)
- proliferative - high oestrogen - thickening of endometrium
- growing endo. glands
- spiral artery formation
- mucus layer
- secretory phase
- more mucus, mucus thickens at day 15
- corpus luteum degenerates - no hormone secretion
- arteries collapse, shedding
Testis
make sperm + testosterone
seminiferous tubules lined by sertoli cells (sperm develop between these and move into lumen)
leydig cells on outside form testosterone
spermatogenesis
spermatogonium divide asymmetrically - 1 primary spermatocyte, 1 more spermatogonium
meiosis 1 - 2 secondary spermatocyte (23X)
Meiosis 2 - 4 spermatids (23I)
spermiogenesis - spermatozoa
accessory glands
seminal vesicles - behind bladder, add 60% volume, alkaline, glucose rich
prostate gland - prostatic fluid, increase sperm motility
bulbourethral gland - thick lubricant
erection
filling with blood
cavernosal arteries + dorsal arteries fill
blood leaks out into lacunae
pushes veins against walls, restricting drainage
penis innervation
- flaccidity - sympathetic - noradrenaline - constriction of vessels
- erection - parasympathetic - nitric oxide - vasodilation
tunica albuginea
surrounds individual chambers of penis - prevents overexpansion
ejaculation
excitement - signal CNS - afferent from CNS
sympathetic stimulation - noradrenaline
contracts epididymis, vas, accessory glands, ejaculatory duct
urethra smooth muscle + bulbospongiosus muscle - external urethral sphincter open
Testosterone functions
- induces mesonephric duct formation
- increased sperm production
- secondary sex characteristics
- increased EPO production (kidney)
PCT absorption
- 65% absorbed in PCT
- glucose
- Na+
- amino acids
- water
loop of henle
descending - passive water reabsorption (ion impermeable)
ascending - active ion reabsorption - Na+, K+, Cl- (water impermeable)
Normal channel proteins in nephron
- Na+/K+ ATPase - 1o AT
- Na+ into lumen
- glucose/Na+ - cotransport/symport
- glucose into cell with Na+ along Na+ gradient
- Na+/Cl-/K+ (NKCC2) contransport
- Na+/Cl- antiporter
- Na+ into cell, Cl- into blood
