An overview and gross structure of the kidney Flashcards
What is the role of the Urinary system?
- our bodies are 60% (male) and 55% (female) water
- total body water = extracellular fluid (1/3) and intracellular fluid (2/3)
- balance of water (and solutes) in the body is crucial
How does the urinary system maintain balance?
By filtering the blood and expelling:
- excess water
- excess salts
- wastes of metabolism
- many toxins and drugs
In order to achieve this, 1200ml of blood flows through the kidneys per minute. A typical person produces 800-2000ml urine/day
What is urine?
Waste product excreted to maintain balance within the body
Normal urine:
- water
- salts
- urea
- metabolites, hormones, small proteins
Urine pH is not tightly regulates (pH ~4.6 - 8) and is influenced by what is excreted
Useful diagnostic tool for disease states
Abnormal urine:
- large proteins (too big to be filtered)
- RBC (too big to be filtered)
- Glucose (filters byt completely reabsorbed)
What does the unrinary system need to be effective?
- delivery system for blood
- selective filtration system
- filtrate recovery mechanism
- system to return recovered, filtered fluid to body
- system to remove filtrate from body
- protection
- ability to communicate with relevant parts of the body
- adaptable to meet the body’s changing needs
What are the main components of the urinary system?
- 2 kidneys
- 2 ureters (one per kidney)
- urinary bladder
- urethra
What does the structure of the kidneys allow for?
- blood to be brought into close proximity with the nephron, for filtering
- blood that has been filtered to leave the kidney
- a pathway for urine to be removed form the kidney, stored and then excreted
- protection
describe the location of they kidneys
- T12-L3
- 11th and 12th ribs protect the kidneys
- convex side of the kidney faces laterally
- medial surface of the kidney has a concave notch called the hilum: for renal blood vessels, lymphatics, nerves and the ureter
- left kidney is higher than right because on right side we have the liver that slightly pushes the right one down more
- retroperitoneal: located on posterior abdominal wall, covered on anterior side by peritoneum
- surrounded, supported and protected by fat (renal fat pad/capsule)
describe the gross structure of the kidneys
- three regions: cortex, medulla, and pelvis
- fibrous capsule around outside for protection
- inner medulla:
- divided into pyramids
- each medullary pyramid ends in a papilla - outer cortex:
- continuous layer
- forms renal columns - cortex and medulla:
- multiple functional lobes
- 5-11 lobes per kidney
Urine pathway: - urine drains from each papilla and collects in a calyx
- calyces join to form the renal pelvis
- pelvis narrows as it exits the hilum to become the ureter
papilla -> minor calyx -> major calyx -> renal pelvis -> ureter
describe the structure of a kidney lobe
A kidney lobe has one medullary pyramid, a cortex that surrounds it, and is made up largely of nephrons - tiny tubes that filter blood from urine. the wiggly part of the nephron is in the cortex, and the straight bit is in the medulla.
describe the blood supply to the kidney
- urine is produced by filtering waste from the blood into the nephron
- filtration occurs in the cortex of the kidney
- renal artery arises from the abdominal aorta (comes through the hilum)
- branching arteries get smaller and smaller until they reach the cortex
- blood is filtered
- veins turn filtered blood from the cortex to the renal vein, then to the inferior vena cava
what happens to blood in the cortex?
- the afferent arteriole delivers blood from the arteries to the glomerulus (which sits inside a renal corpuscle)
- the glomerulus is made of glomerular capillaries and is where filtration occurs
- the efferent arteriole carries blood from the glomerulus to the peritubular capillaries (which surround the nephron loop)
- the peritubular capillaries carry blood to the veins
describe the path of the flow of blood through the kidneys
Blood supply into the cortex to be filtered:
Abdominal aorta
1. renal artery
2. series of arteries
3. afferent arteriole
4. glomerular capillary
Blood supply away from the cortex after being filtered:
Glomerular capillary
1. efferent arteriole
2. peritubular capillaries
3. series of veins
4. renal vein
5. inferior vena cava
describe the nerve supply of the kidneys
- innervation is from a network of autonomic nerves and ganglia called the renal plexus
- sympathetic nerves act to adjust diameter of renal arterioles and thus regulate blood flow (into the glomerulus)
describe some basic features of the nephron
- microscopic functional unit of the kidney
- bulk of kidney made up of nephrons
- filters blood
- selectively reabsorbs or secretes (anything we didn’t filter that we don’t want)
- produces urine
- renal corpuscle (where the glomerulus and the glomerulus capsule meet) - where filtration occurs
- Proximal convoluted tube - toes back anything that we filtered that we don’t want to lose
- Nephron loop - has a thick part and a thin part. useful for salt and water reabsorption
- Distal convoluted tube (DCT)
- Collecting duct (shared by multiple DCTs, both are about fine tuning and regulated reabsorption should we need it)
By this stage the waste product is urine, and the collecting ducts go into the papilla of the pyramids
