MMED1005 Lecture Notes - Lecture 17: Taschen, Renal Pelvis, Kidney Failure
7 Jun 2018
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Hormones in urine formation
Revision:
(Remember: Red lood ells are NOT foud i filtrate of the Bowa’s apsule. Also, no
reasorptio ours i the Bowa’s apsule)
Juxtaglomerular apparatus: intersection between the distal tubule, glomerulus, and
arterioles
Sodium ion reabsorption involves a Na+-K+ io ATPase arrier i the tuular ell’s
basolateral membrane.
- This pump keeps sodium concentration low in the tubular cells and high in the lateral
spaces outside the tubule.
- Other substances are linked to Na+ movement by cotransport.
- In the tubules, the reabsorption of filtered sodium is variable and subject to
hormonal control. More or less is reabsorbed, depending on the needs of the body.
- Water follows reabsorbed sodium by osmosis. Thus, sodium reabsorption has a main
effect on blood volume and blood pressure.
Vertical osmotic gradient in the renal medulla:
- Long loops of Henle project into the concentration gradient
- There is a concentration gradient between the renal cortex and the renal medulla
- It allows the water to be reabsorbed through the gradient
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Summary:
- Afferent arteriole provides oxygenated blood into the glomerulus
- Bowman’s apsule forig the filtrate
- Sodium is reabsorbed actively
- Water follows sodium passively
- Urea is important in helping the concentration gradient, therefore
some is reabsorbed
Tubular secretion:
- H+ and K+ ions, along with organic ions, are tubularly secreted
- H+ ions are secreted and removed from the blood to oppose acidosis
- Potassium secretion is control by aldosterone in the distal
tubule and collecting duct. It is variable and subject to
regulation
- As the basolateral pump transports Na+ from the lateral
spaces, it pumps K+ into the tubular cells (tubular secretion).
Entering the lumen surrounded by these cells, it remains in
the urinary tract for elimination. (K+ has to follow Na+ except
in the opposite direction)
How can glomerular filtration rate (GFR) be controlled?
- You cannot consciously control it
- Effects of constriction of the afferent arteriole: less blood flow → reduce GFR
o
o increase in sympathetic drive → decrease in GFR by constricting the afferent
arterioles
o E.g. car accident → lose blood → blood pressure decreases → look pale
(blood supply to skin reduced)
o Parasympathetic nervous system has NO EFFECT on GFR or the kidneys
- Effects of dilation of the afferent arteriole
o
o decrease in sympathetic drive → dilate afferent arteriole → more blood flow
into capillaries → increase filtration pressure → increase filtration rate (but
not necessarily more urine because there may be more reabsorption)
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Revision: (remember: red (cid:271)lood (cid:272)ells are not fou(cid:374)d i(cid:374) filtrate of the bow(cid:373)a(cid:374)"s (cid:272)apsule. Also, no rea(cid:271)sorptio(cid:374) o(cid:272)(cid:272)urs i(cid:374) the bow(cid:373)a(cid:374)"s (cid:272)apsule) Juxtaglomerular apparatus: intersection between the distal tubule, glomerulus, and arterioles. Sodium ion reabsorption involves a na+-k+ io(cid:374) atpase (cid:272)arrier i(cid:374) the tu(cid:271)ular (cid:272)ell"s basolateral membrane. This pump keeps sodium concentration low in the tubular cells and high in the lateral spaces outside the tubule. Other substances are linked to na+ movement by cotransport. In the tubules, the reabsorption of filtered sodium is variable and subject to hormonal control. More or less is reabsorbed, depending on the needs of the body. Thus, sodium reabsorption has a main effect on blood volume and blood pressure. Long loops of henle project into the concentration gradient. There is a concentration gradient between the renal cortex and the renal medulla. It allows the water to be reabsorbed through the gradient. Afferent arteriole provides oxygenated blood into the glomerulus.
