14.1.314-15 · Homeostasis and Control
Kidney Structure — Cambridge AS & A Level Biology 9700 Revision Notes & Topical Questions
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Lesson summary
14.1.3 Kidney Structure — CAMBRIDGE AS & A LEVEL BIOLOGY 9700 — REVISION NOTES notes: Describe the structure of the human kidney and its associated blood vessels and ducts.Number — humans have two kidneys.Osmoregulatory organ — regulates the water content of the blood, which is v…
- Excretory organ
- Fibrous capsule
- Renal pelvis
- Renal artery
- Renal vein
- Reabsorption
Part 1 of 5Functions of the kidneys
Functions of the kidneys
Number
- Number humans have two kidneys.
Osmoregulatory organ
- Osmoregulatory organ regulates the water content of the blood, which is vital for blood pressure.
Excretory organ
- Excretory organ excretes toxic metabolic waste such as urea and substances in excess such as salts.
Part 2 of 5Associated structures
| Structure | Function |
|---|---|
| Renal artery | Carries oxygenated blood containing urea and salts to the kidney |
| Renal vein | Carries deoxygenated blood with urea and excess salts removed away from the kidney |
| Kidney | Filters blood and regulates its water content |
| Ureter | Carries urine from the kidney to the bladder |
| Bladder | Stores urine temporarily |
| Urethra | Releases urine outside the body |
Part 3 of 5Regions of the kidney
Fibrous capsule
- Fibrous capsule a tough outer layer surrounding the kidney.
Cortex
- Cortex contains the glomerulus, Bowman's capsule, proximal convoluted tubule and distal convoluted tubule.
Medulla
- Medulla contains the loop of Henle and collecting duct.
Renal pelvis
- Renal pelvis the cavity where the ureter joins the kidney.
Part 4 of 5Nephrons
Nephrons
Number
- Number each kidney contains thousands of nephrons.
Function
- Function nephrons form urine and are the functional units of the kidney.
Position
- Position they span the cortex and the medulla.
Part 5 of 5More from the specification
More from the specification
Renal excretion of hepatic waste
- Renal excretion of hepatic waste metabolic deamination in the liver yields nitrogenous urea,
- which causes active filtration within outer renal cortex tissues.
Selective Reabsorption of Glucose in Proximal Convoluted Tubule — All glucose filtered into Bowman's capsule is selectively reabsorbed from the tubular filtrate into peritubular capillaries across the apical membranes of proximal tubule epithelial cells via sodium-glucose symport cotransporters.
Active Transport Mechanisms Across Tubule Membranes
- Basolateral sodium-potassium ATPase pumps continuously expel Na+ into interstitial fluid, maintaining a steep concentration gradient that drives secondary active solute uptake and creates a water potential gradient for water reabsorption.
Homeostatic Role of Insulin in Blood Glucose Regulation
- Insulin released from pancreatic beta cells stimulates glucose uptake via GLUT4 transporters and activates glycogen synthase in target cells, preventing renal threshold exceedance and subsequent glucosuria.
Filtration Barrier Ultrastructure
- High hydrostatic capillary blood pressure forces plasma through the fenestrated endothelium, basement membrane,
- and podocyte filtration slits into the renal lumen, retaining large plasma proteins and blood cells.
Luminal membrane
- Cell surface membrane facing the lumen.
Glucose oxidase
- Enzyme oxidising glucose to gluconic acid and hydrogen peroxide.
Basement membrane
- Collagen and glycoprotein filter layer.
Target cells
- Cells that respond to a particular hormone.
Protein
- A long chain of amino acids containing carbon, hydrogen, oxygen and nitrogen.
Cause
- A factor that directly produces an effect through a known mechanism.
Gradient
- A difference in concentration.
Water potential
- A measure of the tendency of water to move; pure water has the highest.
Negative feedback
- A mechanism in which a change from the set point triggers a response that returns the factor to the set point.
Epithelial cell
- A cell forming a covering or lining layer of tissue.
Amino acid
- The unit from which proteins are made; the sequence decides the protein's shape and function.
Selective reabsorption
- Return of useful substances from the filtrate to the blood.
Glucose
- A simple sugar; the unit that starch, glycogen and cellulose are built from.
Filtrate
- The liquid collected in the Bowman's capsule.
Capillary
- Vessel one cell thick where exchange takes place.
Reabsorption
- Return of useful substances from the filtrate to the blood.
Insulin
- A pancreatic hormone that lowers blood glucose.
Control
- A test on distilled water used for comparison.
Homeostasis
- The maintenance of a constant internal environment.
Plasma
- The liquid part of blood.
Key terms
| Term | Meaning |
|---|---|
| Kidney | Organ that filters blood and regulates its water content. |
| Renal artery | Vessel bringing blood to the kidney. |
| Renal vein | Vessel taking blood from the kidney. |
| Cortex | Outer region of the kidney containing glomeruli. |
| Medulla | Inner region containing loops of Henle and collecting ducts. |
| Renal pelvis | Region where the ureter joins the kidney. |
| Ureter | Tube carrying urine to the bladder. |
Avoid these mistakes
1
Saying the renal vein carries oxygenated blood with urea — the blood is deoxygenated and urea has been removed.
2
Putting loops of Henle in the cortex — they are in the medulla.
3
Mixing up ureter and urethra — the ureter joins the kidney to the bladder, the urethra releases urine.
4
Saying the kidney only excretes — it also regulates water content.
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