Ureters
Paired tubes that convey urine from the kidneys to the bladder (via peristalsis)
Urinary Bladder
Muscular pouch that stores urine
Urethra
Tube that conveys urine out the body
Kidney: Gross Anatomy
- Location: High in the abdominal cavity, retroperitoneal
- Vascular Supply: Renal arteries (from aorta) and renal veins (to inferior vena cava)
- Renal Capsule: Protective layer, made of tough connective tissue
Kidney: Gross Anatomy
- Renal Cortex: “Bark”, outer kidney layer
- Renal columns: Portions of renal cortex that invade the medulla, found between pyramids
- Renal Medulla: “Middle”, inner kidney layer
Renal Pyramids
Pyramidal structures in the medulla that produce urine
Renal Papilla
Tip of the renal pyramid, allow droplets of urine to enter the calyces
Minor & Major Calyces
“Funnels” that capture urine from renal papillae
Renal Pelvis
Collects urine to deliver to the ureters
Renal Corpuscle
Glomerulus and Bowman’s Capsule
Glomerulus
Tufts of fenestrated capillary beds (to filter blood)
Bowmans Capsule
Capsules around glomeruli that capture filtrate
Proximal Convoluted Tubule
- PCT takes filtrate from Bowman’s capsule and performs tubular reabsorption
- Reabsorbs essential nutrients and electrolytes back into the bloodstream via peritubular
capillaries
Nephron Loop/ Loop of Henle
- Important for concentrating urine (vasa recta blood vessels parallel it)
- Descending Limb: Thin segment, reabsorbs water ONLY
- Ascending Limb: Thick segment, reabsorbs salts ONLY
Distal Convoluted Tubule
(DCT)performs tubular secretion in order to mix products in with urine
Collecting Duct
Tube that conveys urine to the renal papilla, and if necessary, can further concentrate
urine
Filtration
- Performed by: Renal Corpuscle
- Blood is filtered through a filtration membrane that excludes by size.
- Filtrate will contain anything small enough to fit through the filtration membrane.
- Filtrate is a combination of waste products, nutrients and electrolytes.
- Entire cells & large molecules stay in the bloodstream.
Countercurrent Multiplier:
Loop of Henle (because osmotic pressure causes it to concentrate
urine)
Countercurrent Exchanger:
Vasa recta (because substances enter and leave these blood
vessels)
Maintaining GFR: Autoregulation
- When systemic BP is low, afferent arteriole dilates to increase GFR
- When systemic BP is high, afferent arterioles constrict to decrease GFR
- Result: GFR is maintained, and kidneys continually filter blood
Blood Pressure Control: The JGA
- What is it? Juxtaglomerular Apparatus – Cluster of cells located near the
glomerulus that are responsible for controlling BP - Granular Cells: Sense pressure. When BP is low, granular cells secrete the enzyme renin.
- Macula Densa Cells: Sense [salt] When urine is dilute, macula densa cells trigger afferent arteriole dilation + granular cell renin secretion
- Mesangial Cells: Allow granular cells & macula densa cells to communicate
The Urinary Bladder
- Bladder mucosa: Transitional epithelium (for distension)
- Bladder muscularis: Detrusor muscle (contracts to squeeze urine out)
The Urethra
Urethral Sphincter Muscles:
* Internal: Smooth muscle (involuntary)
- External: Skeletal muscle (voluntary)
Micturition
- Definition: To urinate/ To void the bladder
- Bladder distension will: Trigger stretch receptors that report to the brain’s micturition
center - The brain’s micturition center will then cause the: Contraction of the detrusor muscle and
relaxation of the external urethral sphincter.
