2. The Urinary System
3. Main Functions of Urinary System
- Kidneys filter blood to keep it pure
- Dispose of nitrogenous wastes from blood
- Regulate the balance of water and electrolytes, acids and
bases
4.
- Kidneys are retroperitoneal organs (see next slide)
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- Superior lumbar region of posterior abdominal wall
- Lateral surface is convex
- Medial surface is concave
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- Hilus *is cleft: vessels, ureters and nerves enter and
leave
- Adrenal glands *lie superior to each kidney
* * 5. 6. 7. Transverse sections showretroperitonealposition of
kidneys Note also: liver, aorta muscles on CT Note layers of
adipose (fat), capsule, fascia 8. 9.
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- Columns of cortex divide medulla into pyramids
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- Darker, cone-shaped medullary or renal pyramids
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- Parallel bundles of urine-collecting tubules
10.
- The human kidney has lobes
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- Pyramid and cortical tissue surrounding it
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- Expanded, funnel shaped, superior part of ureter
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- Branches to form two or three major calices (seen best on right
pic below)
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- Each of these divides again, minor calices: collect urine from
papillae of pyramids
11. The Arteries
- Aortagives off right and left renal arteries
- Renalarteries divides into 5 segmental arteries as enters hilus
of kidney
Segmentalsbranch into lobar arteries Lobarsdivide into
interlobars Interlobarsinto arcuate in junction of medulla and
cortex Arcuatessend interlobular arteries into cortex Cortical
radiatearteries give rise toglomerular arterioles 12. Vasculature
of the kidney
- The glomerular capillary bed is unusual in having arterioles
going both to it and away from it (afferent and efferent), instead
of a vein going away as most
- It is also unusualin having two capillary beds in series (one
following the other)
13.
- Uriniferous tubuleis the main structural and functional
unit
- To left is a single, generalized uriniferous tubule
- More than a million of these tubules act together to form the
urine
- A collecting duct which concentrates urine by removing water
from it
14. Outline
- Uriniferous tubule (anatomical unit for forming urine)
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- Renal corpuscle (in cortex)
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- Glomerulus (tuft of capillaries)
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- Glomerular (Bowmans) capsule
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- Proximal convoluted tubule
15. Outline
- Uriniferous tubule (anatomical unit for forming urine)
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- Renal corpuscle (in cortex)
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- Glomerulus (tuft of capillaries)
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- Glomerular (Bowmans) capsule
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- Proximal convoluted tubule
16. Understand at least this much:
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- a.Fluid is squeezed out of the glomerular capillary bed
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- b.Most nutrients, water ad essential ions are returned to the
blood of the peritubular capillaries
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- c.Moves additional undesirable molecules into tubule from blood
of peritubular capillaries
17. Nephron
- Renal corpuscle: only in cortex
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- Tuft of capillaries calledglomerulus
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- Surrounded by cup-shaped, hollowglomerular (Bowmans)
capsule
- Uriniferous tubule (anatomical unit for forming urine)
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- Renal corpuscle (in cortex)
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- Glomerulus (tuft of capillaries)
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- Glomerular (Bowmans) capsule
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- Proximal convoluted tubule
18. (refer to thispic as we go)
- Visceral layer of capsule haspodocytes
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- Unusual branching epithelial cells
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- Foot processes with slit processes between them
------------------- 19.
- Scanning EM of podocytes clinging to capillaries (left) and
filtration membrane diagram (right)
The capillary pores (fenestrations) restrict the passage of the
largest elements such as blood cells The basement membrane and slit
diaphragm hold back all but the smallest proteins while letting
through small molecules such as water, ions, glucose, amino acids,
and urea 20. Nephron
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- Proximal convoluted tubule
- Uriniferous tubule(anatomical unit for forming urine)
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- Renal corpuscle (in cortex)
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- Glomerulus (tuft of capillaries)
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- Glomerular (Bowmans) capsule
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- Proximal convoluted tubule
21. Proximal convoluted tubule
- Cuboidal epithelial cells with long microvilli (fuzzy
appearance in pics)
- Resorption of water, ions and solutes
- Uriniferous tubule(anatomical unit for forming urine)
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- Renal corpuscle (in cortex)
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- Glomerulus (tuft of capillaries)
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- Glomerular (Bowmans) capsule
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- Proximal convoluted tubule
* 22. Loop of Henle
- Uriniferous tubule(anatomical unit for forming urine)
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- Renal corpuscle (in cortex)
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- Glomerulus (tuft of capillaries)
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- Glomerular (Bowmans) capsule
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- Proximal convoluted tubule
23. Distal convoluted tubule
- Confined to the renal cortex
- Simple cuboidal epithelium
- Selective secretion and resorption of ions
- Uriniferous tubule(anatomical unit for forming urine)
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- Renal corpuscle (in cortex)
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- Glomerulus (tuft of capillaries)
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- Glomerular (Bowmans) capsule
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- Proximal convoluted tubule
24. Classes of nephrons
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- Almost entirely within cortex
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- Renal corpuscles near cortex-medulla junction
25. Collecting Ducts
- Each receives urine from several nephrons
- Run straight through cortex into the deep medulla
- Uriniferous tubule (anatomical unit for forming urine)
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- Renal corpuscle (in cortex)
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- Glomerulus (tuft of capillaries)
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- Glomerular (Bowmans) capsule
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- Proximal convoluted tubule
Collecting Duct 26. Collecting Ducts
- At papilla of pyramid* ducts join to form larger papillary
ducts
- Role: conserve body fluids
Uriniferous tubules 1. Nephron2. Collecting ducts * 27. The
collecting ducts
- The most important role is to conserve body fluids
- When the body must conserve water, the posterior pituitary
gland secretes ADH ( a nti d iuretich ormone)
- ADH increases the permeability of the collecting tubules and
distal tubules to water so more is reabsorbed
- This decreases the total volume of urine
- Alcoholinhibits the release of ADH, so less water is reabsorbed
producing copious amounts of dilute urine (can cause
dehydration)
28. Vessels
- Afferent and efferent arterioles associated with glomerular
capillaries
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- Allows high pressure for forcing filtrate out of blood
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- About 20% of renal plasma flow is filtered each minute
(125ml/min): this is theglomerular filtration rate (GFR), an
important clinical measure of renal function
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- This is about one liter every 8 minutes (only 1% ends up as
urine)
- Peritubular capillaries arise from efferent arterioles
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- Absorb solutes and water from tubule cells
29.
- TheVasa rectais a portion of the peritubular capillary system
which enters the medulla where the solute concentration in the
interstitium is high. It acts with the loop of Henle to concentrate
the urine by a complex mechanism of counter current exchange using
urea. If the vasa recta did not exist, the high concentration of
solutes in the medullary interstitium would be washed out.
____ vasa recta (vessels, continued) The Vasa recta 30.
Histology 31. 32. Juxtaglomerular apparatus
- Regulation of blood pressure
- Granule (jg cells) modified muscle cells secreting renin in
response to falling blood pressure in afferent arteriole
- Macula densa chemoreceptors which secrete renin if solute
concentration falls
Renin-angiotensin mechanism: Sequence of reactions resulting in
aldosterone secretion from adrenal cortex: increases sodium
resorption from distal convoluted tubules: water follows, blood
volume increases and blood pressure increases 33. 34. For studying
Parts of the kidney: 1.Renal pyramid 2.Efferent vessel 3.Renal
artery 4.Renal vein 5.Renalhilum 6.Renal pelvis 7.Ureter 8.Minor
calyx 9.Renal capsule 10.Inferior renal capsule 11.Superior renal
capsule 12.Afferent vessel 13.Nephron 14.Minor calyx 15.Major calyx
16.Renal papilla 17.Renal column 35. The Ureters
- Slender tubes about 25 cm (10 ) long leaving each renal
pelvis
- One for each kidney carrying urine to the bladder
- Descend retroperitonealy and cross pelvic brim
- Enter posterolateral corners of bladder
- Run medially within posterior bladder wall before opening into
interior
- This oblique entry helps prevent backflow of urine
36. Ureters play an active role in transporting urine (its not
just by gravity)
- Transitional epithelium of mucosa stretches when ureters
fill
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- Inner longitudinal, outer circular layers
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- Inferior 3 rdwith extra longitudinal layer)
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- Stimulated to contract when urine in ureter: peristaltic waves
to propel urine to bladder
37. Urinary Bladder
- Lies on pelvic floor posterior to pubic symphysis
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- Males: anterior to rectum
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- Females: just anterior to the vagina and uterus
See also brief atlas 38. 39. 40. 41.
- If full: bladder is spherical and extends into abdominal cavity
(holds about 500 ml or 1 pt)
- If empty: bladder lies entirely within pelvis with shape like
upside-down pyramid
- Urine exits via theurethra
- Trigoneis inside area between ureters and urethra: prone to
infection (see slide 38)
42.
- Bladder wall has three layers (same as ureters)
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- Mucosa with distensible transitional epithelium and lamnia
propria (can stretch)
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- Thick muscularis called thedetrusor muscle
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- 3 layers of highly intermingled smooth muscle
43. The Urethra
- Smooth muscle with inner mucosa
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- Changes from transitional through stages to stratified squamous
near end
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- Drains urine out of the bladder and body
- Male: about 20 cm (8) long
- Female: 3-4 cm (1.5) long
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- Short length is why females have more urinary tract infections
than males -ascending bacteria from stool contamination
Urethra____ urethra 44.
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- Internal: involuntary sphincter of smooth muscle
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- External: skeletal muscle inhibits urination voluntarily until
proper time (levator anni muscle also helps voluntary
constriction)
Males: urethra has three regions (see right) 1. Prostatic
urethra__________ 2. Membranous urethra____ 3. Spongy or penile
urethra_____ _________trigone female 45. With all the labels
46.
- Micturition center of brain: pons
- (but heavily influenced by higher centers)
- Sympathetic: inhibits micturition