Find study materials for any course. Check these out:
Browse by school
Make your own
To login with Google, please enable popups
To login with Google, please enable popups
Don’t have an account?
To signup with Google, please enable popups
To signup with Google, please enable popups
Sign up withor
By contrast, excretion via the digestive tract is the end result of ingestion of either indigestable material or nutritional matter which remains unabsorbed.
Gut provides nutrients to the blood., filtered by kidney.
Sugars, electrolytes, and amino acids are reclaimed from the filtrate at an efficiency of 95% or better. Given the large daily volume of digestive tract secretions, there is very efficient (~99%) water absorption in the gut...
Finally, the kidney is a major factor in the maintenance of skeletal integrity through its ability to vary calcium and phosphate loss into the urine in response to vitamin D, and is the production site of its most biologically active form.
renal hilus (hilum)
The hilus leads into a cavity, the renal sinus, within the kidney which contains fat, blood vessels, nerves, calyces, and renal pelvis.
The medulla is adjacent to the renal sinus. The cortex is redder in appearance and has fine striations known as medullary rays. These striations are due to medullary structures (collecting tubules) extending into the cortex.
the renal pyramids
There are about 6 to 18 lobes.
uriniferous tubule; nephron; collecting tubule
There are 1 to 3 million per kidney. The individual nephron is considered by many as the functional unit and the collecting tubule as sep. entity being part of internal excretory pathway for urine.
proximal convoluted tubule
loop of Henle (descending and ascending)
distal convoluted tubule
Urine exits distal convoluted tubule enters collecting tubule, joins collecting duct system, empties into renal pelvis.
...glomerular capillary endothelium via the glomerular basal lamina.
Podocytes are characterized by numerous cellular extensions that wrap around and enclose the glomerular capillaries.
pedicels or foot processes
The pedicels of adjacent podocytes interdigitate with one another. This arrangement results in slit-like spaces, referred to as filtration slits, between adjacent podocytes.
...the renal pyramids and terminate at the papillae.
The collecting ducts are referred to as the papillary ducts of Bellini.
major calyces; renal pelvis
1) Fluid passes from the bloodstream into the wall of Bowman's capsule during the process of filtration.
2) The efferent arteriole becomes the peritubular capillary, and materials pass back into the capillary during reabsorption.
3) The fluid passes through Henle's loop, then receives more materials from the peritubular capillary by tubular excretion.
4) The blood then passes out a vein, while the fluid (urine) moves to the collecting duct.
Passive diffusion of water, Na+ and Cl- out into medulla; water remains in medulla, while Na+ and Cl- diffuse back into loop.
Smaller volume, hypertonic with respect to plasma.
Impermeable to water, Cl- actively pumped to interstitium; Na+ follows passively
Little change in volume, becomes hypotonic.
Reasborption of Na+, secretion of K+ and H+; regulated by aldosterone; excretion of fixed acids, net H excretion
Decreased pH, lower Na+, and very little bicarbonate, volume can change
Variability permeable to water; regulated by antidiuretic hormone (ADH)
Both volume and osmolarity vary, depending upon ADH secretion by neurohypophysis.
It passes inferiorly on the posterior abdominal wall, enters the pelvis by crossing the pelvic inlet, and then pierces the wall of the urinary bladder at its posterior-lateral aspect. Smooth muscles that are part of bladder act as sphincter.
The bladder stores urine as well as expels it. The excretory pathways and the bladder are lined by the urinary type of epithelium known as transitional epithelium.
It traverses the prostate gland and then exits the pelvic cavity by passing through the pelvic floor (urogenital diaphragm) and terminates at the external urethral orifice of the penis or in the vestibule of the female.
20 cm in length
2 to 6 cm
prostatic, membranous, and penile.
The penile region of the urethra is located with the corpus spongiosum of the penis.
The kidney, during production of urine:
3) excretes foreign...
1) waste products of metabolism
2) fluid volume of the extracellular regions of the body
3) materials from the body
4) type and concentration of salts retained in the body (maintain electrolyte balance)
5) total body water
6) acid-base balance
Water and dissolved solutes from the ultrafiltrate (in the remainder of the nephron) are then selectively reabsorbed. The fluid remaining after completion of this process is urine.
waters, ions, monosaccharides, amino acids, fatty acids, urea, uric acid, and plasma proteins
Some of these blood plasma components (water, ions, and so on) then pass through the glomerular basal lamina, then?
glomerular basal lamina
most material smaller than 70,000 daltons passes through
while material larger than 70,000 daltons will be retained
This gives a true sense of the tremendous efficiency of the kidney, which normally clears 25% of the total cardiac output of blood per minute, forming approx. 120-130 ml of filtrate per minute.
filtration pressure (P); (~25 mm Hg) is net P differential btwn driving force within glomerular arterioles and total back P exerted by osmotic P of blood...
pore size; prevents passage of protein w molecular wts > 70k, red, white blood cells
The cell surface (luminal) facing the tubular opening has many microvilli, called the brush border, precisely like the columnar epithelium of the proximal small intestine (jejenum).
...which subserve active transport.
This efficient system results in reabsorption of
a) >95% of filtered amino acids
b) >98% of filtered glucose
c) 85% of the sodium, chloride, bicarbonate
d) calcium, magnesium, phosphate
...active transport of solutes listed above. Any trace amounts of albumin that escape filtration barrier and enter proximal tubule are taken up by pinocytosis, or are hydrolyzed by membrane-bound enzymes into smaller peptide units.
These materials include creatinine, uric acid, antibiotics, drug metabolites, and radiopaque dyes. It should be recognized that the majority of these materials derive not from the renal parenchyma, but from the blood, so that secretion...
fluid reabsorption in proportion.
Thus, urine that enters the descending loop of Henle remains isosmotic with plasma, although very much diminished in volume.
urine; hypertonic to plasma
The basis for this process is the difference in water permeability btwn the descending (permeable) and ascending (impermeable) limbs of the loop.
passive diffusion down a concentration gradient
Toward end of the descending loop, water which has left the tubular lumen continues to diffuse outward into relatively hypertonic interstitium of the renal medulla, leaving Na+, Cl- to diffuse back.
Sodium ions follow chloride ions passively, thereby diminishing the tonicity of the urine and increasing the tonicity of the interstitium, since water cannot also passively diffuse.
...system of the osmolarity of plasma which is under neuroendocrine regulatory control.
The largest portion of fixed acid is generally phosphate, followed by lactate and betahydroxybutyrate. In contrast to the major body buffer system of carbonic acid, which can be converted to CO2 and excreted easily via the lungs, these...
The pituitary gland, or _________________, regulates plasma osmolarity by exerting control over water reabsorption at the distal and collecting ducts.
It does so by secretion of the antidiuretic hormone (ADH); since "diuresis" implies urinary fluid excretion, ADH diminished urinary volume by increasing the permeability of the distal tubule and collecting ducts to water.
...inhibiting further ADH secretion.
A frequent result of head trauma or severe cerebral hypoxia is the "syndrome of inappropriate ADH secretion," - urine flow becomes very slow and plasma osmolarity decreases to dangerous levels.
The distal convoluted tubules also participate in maintaining the acid-base balance of the blood by adding hydrogen and ammonium ions into the filtrate.
antidiuretic hormone (ADH) secreted by the posterior lobe of the pituitary gland (heurohypophysis).
The presence of this hormone makes these tubules more permeable to water. Water exits the collecting tubules and passes into the interstitium.
Increase in ADH leads to resorption of water resulting in more ____________ urine. A decrease in ADH decreases resorption, ergo ___________ urine.
...into and out of the vessel lumen.
This establishes a countercurrent exchange system between the arterioles and venulae rectae.
Sign up for free and study better.
Get started today!