Notes
Urinary system
- Kidneys filter blood; ureters, bladder and urethra carry and store urine. The nephron has a glomerulus, Bowman's capsule, PCT, loop of Henle, DCT and collecting duct.
- Urine formation: filtration, reabsorption, secretion. Nearly all glucose and most water are reabsorbed. ADH, aldosterone, renin and ANP regulate water and sodium balance.
- Blood pH of 7.35 to 7.45 is maintained by buffers, breathing and the kidneys.
Reproductive system
- Male: testes (sperm, testosterone), epididymis, vas deferens, accessory glands. Female: ovaries, uterine tubes, uterus, cervix, vagina.
- Hormones: GnRH, FSH, LH, estrogen, progesterone, testosterone. An LH surge triggers ovulation; the corpus luteum makes progesterone; falling hormones cause menstruation.
- Fertilization occurs in the uterine tube. The blastocyst implants in the endometrium; the placenta makes hCG. Birth is driven by oxytocin through positive feedback.
Topics in this unit
Each topic has its own short notes and practice.
Practice
Normally all glucose is reabsorbed. High blood glucose can exceed the transport maximum.
Dehydration increases ADH, causing more water to be reabsorbed.
Blood pressure pushes filtrate out of the glomerulus into Bowman's capsule.
The two blood supplies stay separate, with exchange across thin membranes.
The LH surge at about day 14 triggers the release of the egg.
Without hCG the corpus luteum degenerates, progesterone falls and menstruation follows.
Free response
Write your answer first, then open the scoring guide.
Free-response question
A woman has a 28-day cycle with ovulation on day 14. A man at the same time has low blood volume after a day of heavy exercise in the heat and drinks very little water.
(a) Describe the roles of FSH and LH in the woman's cycle.
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FSH stimulates a follicle to grow and make estrogen in the first half of the cycle. A surge of LH around day 14 triggers ovulation, and LH also supports the corpus luteum.
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(b) Explain what happens if the egg is not fertilized, in terms of hormones and the uterine lining.
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The corpus luteum degenerates, so progesterone and estrogen levels fall. The endometrium cannot be maintained and is shed in menstruation.
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(c) Explain how the man's kidneys respond to the low blood volume.
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ADH is released, so collecting ducts reabsorb more water. Low blood pressure also activates renin, angiotensin II and aldosterone, which increase sodium and water retention. The result is a small volume of concentrated urine.
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