203 UG - Physiology Flashcards
The excretory function of kidney - What does the kidney excrete?
Metabolic waste
- urea
- creatinine
- uric acid
- bilirubin
Foreign chemicals
- drugs
List the functions of kidney (7)
Regulation of H2O & electrolyte balance
Regulates body fluid osmolarity & electrolyte conc
Regulates bp by excretion of Na2+ & H2O
Regulation of acid base balance
Production of erythropoietin
Formation of 1,25 dihydroxycholecalciferol
Gluconeogenesis
Pathway of renal blood supply
Aorta → renal artery → interlobar artery → arcuate artery → interlobular artery → afferent arteriole → glomerular capillary
Pathway of renal blood drainage
Efferent arteriole → peritubular capillaries → interlobular vein → arcuate vein → interlobar vein → renal vein
Nephron pathway
Glomerulus → Bowman’s capsule → PCT → Loop of Henle → Macula densa → DCT → Collecting tubule
Cortical nephrons
70-80% of nephrons Glomeruli in cortex Short loops of Henle reaching outer medulla Peritubular capillaries Excretion function
Juxta-medullary nephrons (5)
20-30% of all nephrons
Glomeruli at junction between medulla & cortex
Long loops of Henle reaching inner medulla
Vasa recta
Concentration of urine
Urinary excretion rate of a substance =
filtration rate - reabsorption rate + secretion rate
What is the main function of kidney?
Excretion
What does excretion of kidney depend on?
Filtration, reabsorption & secretion
Which nephron is involved in concentrating urine?
Juxta-medullary nephrons
Filtration fraction =
Glomerular filtration rate (GFR) / Renal plasma flow (RPF)
Normal glomerular filtration rate (GFR)
125 ml/min
180 L/day
Normal renal plasma flow (RPF)
625 ml/min
What are the 3 layers of glomerular capillary membrane?
- Fenestrated endothelium - -ve charged
- Basement membrane - contains collagen & -ve charged proteoglycans
- Epithelial cells - podocytes w foot process & slit pores in between - -ve charged
What are the properties of substances that are filtered in the kidney?
Depends on size & charge
Small & positive
Sodium & glucose are ______ filtered;
Albumin is ______ filtered.
(kidney filtration)
freely; poorly
Why are positively charged substances more easily filtered in the kidney?
Filtration membrane is negative, positive and negative attract
Minimal change neuropathy
Negative charges of filtration membrane lost
- autoimmune disease
- proteinuria - albuminuria
GFR =
Kf × net filtration pressure
Forces Favoring Filtration
Glomerular hydrostatic pressure
Bowman’s capsule colloid osmotic pressure
Forces Opposing Filtration
Bowman’s capsule hydrostatic pressure
Glomerular capillary colloid osmotic pressure
Why is Bowman’s capsule colloid osmotic pressure usually 0?
Proteins are not filtered
Kf depends on?
Area & permeability of filtration membrane
Why is high blood flow needed for kidney excretory function?
High O2 consumption related to sodium reabsorption
Renal blood flow = ?
(Renal artery pressure - renal vein pressure) / total renal vascular resistance
Tubulo-glomerular feedback
Mediated by the juxta-glomerular apparatus
Macula densa sense less NaCl → signal JG cells secrete renin → dilate afferent arteriole → more filtration
GFR depends on?
Kf
Starling forces
What is autoregulation in kidney?
Maintains renal blood flow & GFR in spite of changes in BP
What helps in autoregulation?
Tubulo-glomerular feedback
Myogenic mechanism
Smooth muscles are ______;
Skeletal muscles are ______
involuntary; voluntary
Internal sphincter is ______;
External sphincter is ______.
involuntary (smooth muscle); voluntary (skeletal muscle)
2 major parts of bladder
Body
Neck
Mucosa of trigone vs mucosa of other parts of bladder
Mucosa of trigone is smooth
Others are folded - rugae
Detrusor
Smooth muscle of bladder
Main innervation of the bladder
Pelvic nerve - connect spinal cord through sacral plexus: S2, S3, S4
Movement of urine from the kidney to the bladder
Urine formed in collecting duct → enters minor calyx → contraction of smooth muscle in calyx, pelvis, ureter → moves urine to bladder
Peristaltic activity is ______ by parasympathetic stimulation; ______ by sympathetic stimulation.
increased; decreased
What prevents vesicoureteral reflux?
A special one-way valve system in the ureter
Micturition reflex
Caused by stretch of bladder when filled w urine → sensory info carried to sacral segment of spinal cord → pelvic nerve → motor impulses (through parasympathetic nerves) → contraction of detrusor & relaxation of internal sphincter
Self regenerative of micturition reflex
Initial contraction of the bladder activates the stretch receptors to cause a greater increase in sensory impulses from the bladder and posterior urethra → further increase in reflex contraction of the bladder
→ cycle is repeated until the bladder has reached a strong degree of contraction.
Effect of higher centers on micturition reflex
Facilitatory & inhibitory centres in brainstem & cortex
- keep micturition reflex inhibited until it’s needed
What initiates voluntary control of micturition?
Initiated by contracting abdominal muscles
Micturation reflex is a ______ reflex.
spinal
What are the male & female gonads?
Male - testis
Female - ovary
SRY
Sex determining region of Y
Present → testes → produce TDF (Testis-determining factor)
Absent → ovaries
Differentiation of internal genitalia - male
SRY present → Leydig cells produce testosterone → proliferation of Wolffian duct → epididymis, vas deferens, seminal vesicles, ejaculatory duct
SRY present → Sertoli cells produce AMH → regression of Mullerian duct
Differentiation of internal genitalia - female
SRY absent → absence of testosterone → regression of Wolffian duct
SRY absent → absence of AMH → progression of Mullerian duct → uterus, fallopian tubes, inner vagina
Differentiation of outer genitalia - male
Testosterone converted to DHT by 5α-reductase → development of penis, scrotum, prostate
Differentiation of outer genitalia - female
Absence of testosterone → development of outer vagina, female external genitalia
Androgen insensitivity syndrome
Genotype: XY - w testes
Phenotype: Female - w external genitalia & vagina
5α-reductase deficiency
Testosterone ↛ DHT
Male internal genitalia
Female external genitalia
Abnormalities in SRY
During crossing over SRY may go to X chromosome → female w male external genitalia
Male chromosome lack SRY → male w female external genitalia
Turner syndrome
XO
Nondisjunction of chromosomes during meiosis
Female internal & external genitalia
Klinefelter syndrome
47 XXY
Male external genitalia & 2° sexual characteristics
Down syndrome
Trisomy 21
Nondisjunction of autosome
True hermaphroditism
Have both testes & ovary
雌雄同體
How is puberty activated?
Release of gonadotropins during adolescence
First sign of puberty - males
Gonadarche - enlargement of testes
First sign of puberty - females
Thelarche - development of breast
Oogenesis
Primordial germ cell → oogonium (w primordial follicle) → primary oocyte (w primary follicle) →
Meiosis I
→ secondary oocyte (w mature follicle) → ovulated secondary oocyte
When does meiosis II occur during oogenesis?
During fertilisation
When does meiosis I occur during oogenesis?
During puberty
Ovarian cycle (10)
- GnRH acts on anterior pituitary → release FSH & LH
- Primordial follicles become primary follicles
- Develop many layers of granulosa cells
- Increase FSH → growth of 6-12 primary follicles - granulosa cell layers increase
- Theca cell layer (internal & external) develops outside granulosa
- Granulosa cells secrete fluid rich in estrogen - forms antrum
- Estrogen increases FSH receptor
- 1 follicle w many FSH receptors will mature to ovulate (14th day)
- Increase in estrogen decreases FSH
- Other follicles - atresia
LH surge
Just before ovulation LH levels increase → the release of ovum from the ovary
Corpus luteum
Remaining follicle w/o ovum after ovum released
Hormones of Menstrual cycle
FSH → stimulates estrogen → inhibits FSH
→ stimulate LH → inhibits estrogen
→ stimulate progesterone → inhibits LH
Corpus luteum is maintained during?
first 3 months of pregnancy, by hCG
3 phases of the uterine cycle
Proliferative - endometrium becomes thicker
Secretory - secretes hormones for pregnancy/menstruation
Menstruation - shedding of endometrium
Which phase of the uterine cycle is fixed?
Secretory phase - 12 days
Corpus luteum regresses 12 days after formation
Regulation of hormones in menstrual cycle
Mostly - negative feedback - estrogen & progesterone provide negative feedback to the hypothalamus and pituitary gland
In days 12 - 14 - positive feedback - estrogen provides positive feedback to the hypothalamus and pituitary gland → LH surge → ovulation
Indication of ovulation
Pregnanediol level in urine - indicates progesterone secretion
Body temp increase by 0.5°C
Liver dysfunction increases ______ levels in the blood
oestrogen
Function of female sex hormone - oestrogen
Female secondary sexual characteristics
Function of female sex hormone - progesterone
Prepares uterus for implantation
Prepares breast for milk secretion - increase alveoli & lobules in breast
Oestrogen causes the ______ phase in menstrual cycle.
proliferative
Milk secretion is stimulated by?
Prolactin
Milk ejection requires?
Oxytocin
Contraction of myoepithelial cells
Why does menopause occur?
Primordial follicles degenerate after 45 years
Decreased secretion of oestrogen → menstrual cycles stop
Ovulation is caused by?
LH surge
What causes LH surge?
Positive feedback by oestrogen
______ causes proliferative changes in uterus;
______ causes secretory changes in uterus
Ostrogen; Progesterone
Where is egg fertilized?
Amupulla of fallopian tube
What cells facilitate implantation?
Trophoblast cells
Arterial supply & venous drainage of placenta
Arterial supply: uterine artery
Venous drainage: uterine veins
What increases foetal oxygenation?
High affinity of HbF
High RBC
Double Bohr effect
What secrete hCG?
Syncytial trophoblast cells of blastocyst
Function of hCG
Maintains corpus luteum for 3 months
Corpus luteum secretes?
Progesterone & estrogen
High levels of hormones during pregnancy for?
Preventing ovulation & menstruation
What happens after 3 months in pregnancy, after corpus luteum degenerates?
Placenta takes over - placental synctial trophoblast cells secrete estrogen & progesterone
Maternal changes during pregnancy
↑ requirement for hormones & nutrients ↑ salt & water retention ↑ BMR ↑ blood volume ↑ CO
Positive feedback of parturition
Helped by oxytocin
- Baby’s head stretches cervix
- Cervical stretch excites fundic contraction
- Fundic contraction pushes baby down & stretches cervix more
- Cycle repeats
What hormone helps in the development of ducts in the breast?
Oestrogen
What hormone helps in the development of alveoli & lobules in the breast?
Progesterone
What causes amenorrhea in pregnancy?
High levels of estrogen and progesterone
