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MBBS > 203 UG - Physiology > Flashcards

203 UG - Physiology Flashcards

1
Q

The excretory function of kidney - What does the kidney excrete?

A

Metabolic waste

  • urea
  • creatinine
  • uric acid
  • bilirubin

Foreign chemicals
- drugs

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2
Q

List the functions of kidney (7)

A

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

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3
Q

Pathway of renal blood supply

A

Aorta → renal artery → interlobar artery → arcuate artery → interlobular artery → afferent arteriole → glomerular capillary

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4
Q

Pathway of renal blood drainage

A

Efferent arteriole → peritubular capillaries → interlobular vein → arcuate vein → interlobar vein → renal vein

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5
Q

Nephron pathway

A

Glomerulus → Bowman’s capsule → PCT → Loop of Henle → Macula densa → DCT → Collecting tubule

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6
Q

Cortical nephrons

A 
70-80% of nephrons
Glomeruli in cortex
Short loops of Henle reaching outer medulla
Peritubular capillaries
Excretion function
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7
Q

Juxta-medullary nephrons (5)

A

20-30% of all nephrons
Glomeruli at junction between medulla & cortex
Long loops of Henle reaching inner medulla
Vasa recta
Concentration of urine

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8
Q

Urinary excretion rate of a substance =

A

filtration rate - reabsorption rate + secretion rate

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9
Q

What is the main function of kidney?

A

Excretion

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10
Q

What does excretion of kidney depend on?

A

Filtration, reabsorption & secretion

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11
Q

Which nephron is involved in concentrating urine?

A

Juxta-medullary nephrons

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12
Q

Filtration fraction =

A

Glomerular filtration rate (GFR) / Renal plasma flow (RPF)

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13
Q

Normal glomerular filtration rate (GFR)

A

125 ml/min

180 L/day

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14
Q

Normal renal plasma flow (RPF)

A

625 ml/min

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15
Q

What are the 3 layers of glomerular capillary membrane?

A
  1. Fenestrated endothelium - -ve charged
  2. Basement membrane - contains collagen & -ve charged proteoglycans
  3. Epithelial cells - podocytes w foot process & slit pores in between - -ve charged
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16
Q

What are the properties of substances that are filtered in the kidney?

A

Depends on size & charge

Small & positive

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17
Q

Sodium & glucose are ______ filtered;
Albumin is ______ filtered.
(kidney filtration)

A

freely; poorly

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18
Q

Why are positively charged substances more easily filtered in the kidney?

A

Filtration membrane is negative, positive and negative attract

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19
Q

Minimal change neuropathy

A

Negative charges of filtration membrane lost

  • autoimmune disease
  • proteinuria - albuminuria
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20
Q

GFR =

A

Kf × net filtration pressure

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21
Q

Forces Favoring Filtration

A

Glomerular hydrostatic pressure

Bowman’s capsule colloid osmotic pressure

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22
Q

Forces Opposing Filtration

A

Bowman’s capsule hydrostatic pressure

Glomerular capillary colloid osmotic pressure

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23
Q

Why is Bowman’s capsule colloid osmotic pressure usually 0?

A

Proteins are not filtered

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24
Q

Kf depends on?

A

Area & permeability of filtration membrane

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25
Why is high blood flow needed for kidney excretory function?
High O2 consumption related to sodium reabsorption
26
Renal blood flow = ?
(Renal artery pressure - renal vein pressure) / total renal vascular resistance
27
Tubulo-glomerular feedback
Mediated by the juxta-glomerular apparatus Macula densa sense less NaCl → signal JG cells secrete renin → dilate afferent arteriole → more filtration
28
GFR depends on?
Kf | Starling forces
29
What is autoregulation in kidney?
Maintains renal blood flow & GFR in spite of changes in BP
30
What helps in autoregulation?
Tubulo-glomerular feedback | Myogenic mechanism
31
Smooth muscles are ______; | Skeletal muscles are ______
involuntary; voluntary
32
Internal sphincter is ______; | External sphincter is ______.
involuntary (smooth muscle); voluntary (skeletal muscle)
33
2 major parts of bladder
Body | Neck
34
Mucosa of trigone vs mucosa of other parts of bladder
Mucosa of trigone is smooth | Others are folded - rugae
35
Detrusor
Smooth muscle of bladder
36
Main innervation of the bladder
Pelvic nerve - connect spinal cord through sacral plexus: S2, S3, S4
37
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
38
Peristaltic activity is ______ by parasympathetic stimulation; ______ by sympathetic stimulation.
increased; decreased
39
What prevents vesicoureteral reflux?
A special one-way valve system in the ureter
40
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
41
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.
42
Effect of higher centers on micturition reflex
Facilitatory & inhibitory centres in brainstem & cortex | - keep micturition reflex inhibited until it's needed
43
What initiates voluntary control of micturition?
Initiated by contracting abdominal muscles
44
Micturation reflex is a ______ reflex.
spinal
45
What are the male & female gonads?
Male - testis | Female - ovary
46
SRY
Sex determining region of Y Present → testes → produce TDF (Testis-determining factor) Absent → ovaries
47
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
48
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
49
Differentiation of outer genitalia - male
Testosterone converted to DHT by 5α-reductase → development of penis, scrotum, prostate
50
Differentiation of outer genitalia - female
Absence of testosterone → development of outer vagina, female external genitalia
51
Androgen insensitivity syndrome
Genotype: XY - w testes Phenotype: Female - w external genitalia & vagina
52
5α-reductase deficiency
Testosterone ↛ DHT Male internal genitalia Female external genitalia
53
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
54
Turner syndrome
XO Nondisjunction of chromosomes during meiosis Female internal & external genitalia
55
Klinefelter syndrome
47 XXY | Male external genitalia & 2° sexual characteristics
56
Down syndrome
Trisomy 21 | Nondisjunction of autosome
57
True hermaphroditism
Have both testes & ovary 雌雄同體
58
How is puberty activated?
Release of gonadotropins during adolescence
59
First sign of puberty - males
Gonadarche - enlargement of testes
60
First sign of puberty - females
Thelarche - development of breast
61
Oogenesis
Primordial germ cell → oogonium (w primordial follicle) → primary oocyte (w primary follicle) → Meiosis I → secondary oocyte (w mature follicle) → ovulated secondary oocyte
62
When does meiosis II occur during oogenesis?
During fertilisation
63
When does meiosis I occur during oogenesis?
During puberty
64
Ovarian cycle (10)
1. GnRH acts on anterior pituitary → release FSH & LH 2. Primordial follicles become primary follicles 3. Develop many layers of granulosa cells 4. Increase FSH → growth of 6-12 primary follicles - granulosa cell layers increase 5. Theca cell layer (internal & external) develops outside granulosa 6. Granulosa cells secrete fluid rich in estrogen - forms antrum 7. Estrogen increases FSH receptor 8. 1 follicle w many FSH receptors will mature to ovulate (14th day) 9. Increase in estrogen decreases FSH 10. Other follicles - atresia
65
LH surge
Just before ovulation LH levels increase → the release of ovum from the ovary
66
Corpus luteum
Remaining follicle w/o ovum after ovum released
67
Hormones of Menstrual cycle
FSH → stimulates estrogen → inhibits FSH → stimulate LH → inhibits estrogen → stimulate progesterone → inhibits LH
68
Corpus luteum is maintained during?
first 3 months of pregnancy, by hCG
69
3 phases of the uterine cycle
Proliferative - endometrium becomes thicker Secretory - secretes hormones for pregnancy/menstruation Menstruation - shedding of endometrium
70
Which phase of the uterine cycle is fixed?
Secretory phase - 12 days | Corpus luteum regresses 12 days after formation
71
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
72
Indication of ovulation
Pregnanediol level in urine - indicates progesterone secretion Body temp increase by 0.5°C
73
Liver dysfunction increases ______ levels in the blood
oestrogen
74
Function of female sex hormone - oestrogen
Female secondary sexual characteristics
75
Function of female sex hormone - progesterone
Prepares uterus for implantation | Prepares breast for milk secretion - increase alveoli & lobules in breast
76
Oestrogen causes the ______ phase in menstrual cycle.
proliferative
77
Milk secretion is stimulated by?
Prolactin
78
Milk ejection requires?
Oxytocin | Contraction of myoepithelial cells
79
Why does menopause occur?
Primordial follicles degenerate after 45 years | Decreased secretion of oestrogen → menstrual cycles stop
80
Ovulation is caused by?
LH surge
81
What causes LH surge?
Positive feedback by oestrogen
82
______ causes proliferative changes in uterus; | ______ causes secretory changes in uterus
Ostrogen; Progesterone
83
Where is egg fertilized?
Amupulla of fallopian tube
84
What cells facilitate implantation?
Trophoblast cells
85
Arterial supply & venous drainage of placenta
Arterial supply: uterine artery | Venous drainage: uterine veins
86
What increases foetal oxygenation?
High affinity of HbF High RBC Double Bohr effect
87
What secrete hCG?
Syncytial trophoblast cells of blastocyst
88
Function of hCG
Maintains corpus luteum for 3 months
89
Corpus luteum secretes?
Progesterone & estrogen
90
High levels of hormones during pregnancy for?
Preventing ovulation & menstruation
91
What happens after 3 months in pregnancy, after corpus luteum degenerates?
Placenta takes over - placental synctial trophoblast cells secrete estrogen & progesterone
92
Maternal changes during pregnancy
``` ↑ requirement for hormones & nutrients ↑ salt & water retention ↑ BMR ↑ blood volume ↑ CO ```
93
Positive feedback of parturition
Helped by oxytocin 1. Baby's head stretches cervix 2. Cervical stretch excites fundic contraction 3. Fundic contraction pushes baby down & stretches cervix more 4. Cycle repeats
94
What hormone helps in the development of ducts in the breast?
Oestrogen
95
What hormone helps in the development of alveoli & lobules in the breast?
Progesterone
96
What causes amenorrhea in pregnancy?
High levels of estrogen and progesterone

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