Describe the gross anatomy of the kidney
- Location: Retroperitoneal space, on
either side of the spine between T12
and L3 vertebrae. - Size: About 11 cm long, 6 cm wide, and 3
cm thick. - External Features: Renal capsule (fibrous
covering), renal cortex (outer layer),
renal medulla (inner region with renal
pyramids). - Internal Features:
- Renal Pelvis: Funnel-shaped structure
collecting urine from the kidney. - Renal Pyramids: Cone-shaped tissues
within the medulla. - Renal Columns: Extensions of cortical
tissue between pyramids. - Calyces (major and minor): Chambers
receiving urine from the pyramids and
passing it to the renal pelvis.
- Renal Pelvis: Funnel-shaped structure
Describe the anatomy and function of a nephron.
- Components:
- Renal Corpuscle: Includes Bowman’s
capsule and glomerulus; site of blood
filtration. - Proximal Convoluted Tubule (PCT):
Reabsorbs nutrients, ions, and water. - Loop of Henle: Descending and
ascending limbs; concentrates urine
by reabsorbing water and salt. - Distal Convoluted Tubule (DCT):
Further modifies filtrate through
reabsorption and secretion. - Collecting Duct: Collects urine from
multiple nephrons, final adjustments
to urine composition.
- Renal Corpuscle: Includes Bowman’s
- Function: Filters blood, reabsorbs necessary substances, secretes waste products, and regulates fluid and electrolyte balance
Explain and distinguish between filtration, absorption, and secretion.
- Filtration: Blood pressure forces water and solutes from the glomerulus into Bowman’s capsule, forming filtrate.
- Absorption: Movement of water and solutes from the filtrate back into the bloodstream, primarily in the PCT, loop of Henle, DCT, and collecting duct.
- Secretion: Transfer of substances from the blood into the filtrate for excretion, occurring mainly in the PCT and DCT.
Discuss how renal function is evaluated.
Blood Tests:
* Serum Creatinine: Indicator of kidney
function; high levels suggest impaired
function.
* Blood Urea Nitrogen (BUN): Measures
urea levels; elevated levels indicate
reduced kidney function.
Urine Tests:
* Urinalysis: Examines the physical and
chemical properties of urine.
* Glomerular Filtration Rate (GFR):
Estimates the rate of blood flow
through the glomeruli; normal GFR is
90-120 mL/min.
- Imaging: Ultrasound, CT scan, or MRI to visualize kidney structure.
- Biopsy: Analysis of kidney tissue for diagnostic purposes.
Describe urinary elimination.
Process:
* Urine Formation: Filtration,
reabsorption, and secretion in
nephrons.
* Urine Transport: Urine moves from
the kidneys through the ureters to the
bladder.
* Urine Storage: Bladder stores urine
until elimination.
* Micturition (Urination): Voluntary and
involuntary control mechanisms expel
urine from the bladder through the
urethra.
- Regulation:
- Nervous System: Parasympathetic
nervous system stimulates bladder
contraction. - Sphincter Control: Internal
(involuntary) and external (voluntary)
sphincters control urine release.
- Nervous System: Parasympathetic
Describe the processes of filtration, absorption, and secretion in the nephron.
- Filtration: Blood pressure forces plasma through the glomerular capillaries into Bowman’s capsule, excluding cells and large proteins.
- Absorption: Essential substances (glucose, amino acids, ions) and water are reabsorbed from the filtrate back into the bloodstream, primarily in the PCT.
- Secretion: Additional waste products (hydrogen ions, potassium, creatinine) are secreted from the blood into the filtrate, mainly in the PCT and DCT.
Describe the process of urinary elimination.
- Kidneys: Produce urine through filtration, reabsorption, and secretion.
- Ureters: Transport urine from the kidneys to the bladder using peristaltic waves.
- Bladder: Stores urine until it is excreted; stretches to accommodate varying volumes.
- Urethra: Conveys urine from the bladder to the outside of the body; sphincters regulate flow.
- Micturition Reflex: Triggered by bladder distension; involves both involuntary (internal sphincter) and voluntary (external sphincter) control.
