Urinary System: Kidneys Flashcards
Urinary System: Kidneys
Name the components of the urinary system and their functions
1) Kidneys- is for Urine forming
2) Ureters- paired tubes that transport urine from the kidneys to be he urinary bladder
3) Urinary Bladder- temporary storage reservoir for urine
4) Urethra- tube that carries urine from th bladder to the body exterior
Description of the gross Anatomy of the Kidney and its coverings
MORE ABOUT THE SIZE
- Bean shaped and a mass of about 150g
- Average dimensions of 11cm long, 6cm wide and 3cm thick
Description of the gross Anatomy of the kidney and it’s coverings
ABOUT LOCATION:
- Lie in a retroperitoneal position in the superior lumbar region (T12-L3)
- Right kidney crowded by the liver
- Slightly lower than the left
- Lateral surface is convex
- Medial surface is concave and has a vertical cleft: renal hilum
- Internal space within the kidney: renal sinus
- Atop each kidney is the adrenal gland (endocrine gland)
What are the 3 layers of supportive tissue surrounding each kidney
From superficial to deep
1) Renal Fascia- outer layer of the dense fibrous connective tissue that anchors the kidney and the adrenal gland to surrounding structure.
2) Peri-renal fat capsule- fatty mass that surrounds the kidney and cushions it against blows
3) Fibrous capsule- transparent capsule that prevents infections in surrounding regions from spreading to the kidney
3 Distinct regions to the internal kidney
1) Renal cortex
2) Renal medulla
3) Renal pelvis
Description of Renal Cortex
- Most superficial region, light colored and has a granular appearance.
- Renal columns inwards extensions of cortical tissue separate the pyramids
Description of the Renal Medulla
- Darker reddish brown, exhibits cone-shaped tissue masses called Renal pyramids.
- The broad base of each pyramid faces towards the cortex and it’s apex (papilla) points internally.
- The pyramids appeared striped because they are formed of parallel bundles of urine-collecting tubules and capillaries.
- Each pyramid and its surrounding cortical tissue constitute one of approximately 8 lobes of a kidney.
Description of the Renal pelvis
- A funnel shaped tube is continuous with the ureter leaving the hilum.
- Branching extensions of the pelvis form several minor calyces (cup shaped areas that enclose the papillae)
- The calyces collect urine, which drains, continuously from the papilla and empty it into the Renal pelvis.
- The urine then flows thru the Renal pelvis into the ureter, which moves it to the bladder to be stored.
- The walls of the calyces, pelvis and ureter contain smooth muscle that contracts rhythmically to propel urine by peristalsis.
Description of histological arrangement of the functional units of the kidney, the NEPHRON
Description of the Renal corpuscle
Each Renal corpuscle consists of a tuft or capillaries called glomerulus and a cup shaped hollow structure called the Glomerular capsule (or Bowman’s capsule).
The glomerular capsule completely surrounds the glomerulus and is continuous with its renal tubules
Description of the Glomerulus
- Endothelium of glomerular capillaries is fenestrated (penetrated by many pores), which makes these capillaries to be POROUS.
- This property allows large amounts of solute-rich but virtually protein-free fluid to pass from the blood into the Glomerulus capsule.
- This plasma-derived fluid or filtrate is the raw material that the Renal tubules process to form urine.
Description of the Glomerular Capsule
- The glomerular capsule has an external parietal layer visceral layer that clings to the Glomerular capillaries.
- The parietal layer is simple squamous epithelium, that contributes to the capsule structure but plays no part in forming filtrate.
- The visceral layer, which clings to the glomerular capillaries, consists of highly modified, branching epithelial cells called PODOCYTES.
- The octopus-like PODOCYTES terminate in foot processes, which interdigitate as they cling to the basement membrane of the glomerulus.
- The clefts or openings between the foot processes are called filtration slits.
- Through these slits, filtrate enters the capsular space inside the glomorular capsule.
- We describe the filtration membrane, the filter that lies between the blood in the glomerulus and the filtrate in the capsular space.
Description of the Renal tubules
- The renal tubule is 3cm long and had 3 major parts.
- It leaves the glomerular capsule as coiled Proximal Convoluted Tubule, drops into a hairpin poop callled the nephron loop (loop of Henle), then winds and twists again as the Distal Convoluted Tubule before emptying into a collecting duct.
- The meandering nature of the Renal Tubule increases its length and enhances its filtrate processing capabilities.
- Throughout their length, the Renal Tubule and collecting duct consist of a single layer of polar epithelial cells on a basement membrane.
In Renal Tubules
Describe the Proximal Convoluted Tubule
- The walls of the PCT are formed by cuboidal epithelial cells with large mitochondria and their apical (luminal) surfaces bear dense microvilli.
- Just as in the intestine, this brush border increases the surface area and capacity for reabsorbing H2O and solutes from the filtrate and secreting substances into it.
In Renal Tubules:
Describe the Nephron Loop
- U-shaped Nephron loop called loop of Henle, has descending and ascending limbs.
- The proximal part of the descending limb is continuous with the proximal Tubule and its cells are similar.
- The rest of the descending limb, called the descending thin limb, consists of a simple squamous epithelium.
- The epithelium becomes cuboidal or even low columnar in the ascending part of the Nephron loop, which is therefore called the thick ascending limb.
In Renal Tubules:
Describe the Distal Convoluted Tubule
-The epithelial cells of the Distal Convoluted Tubule, like those of the Proximal Convoluted Tubule, are cuboidal and confined to the cortex, but they are thinner and almost entirely lack microvilli.
