Structure of the Kidney

Question 1

What is the role of the urinary system?

Answer 1

About 55-60% of our bodies are made of water (males have more as they have more muscular tissue, females have more adipose tissue, muscular tissue has more water)
1/3 of the body water is extracellular (fluid between cells and fluid within blood vessels)
2/3 of the body water is intracellular
Balance of water and solutes in the body is crucial

Question 2

How does the urinary system maintain balance?

Answer 2

Urinary system filters blood and expels various substances - excess water, excess salts (sodium, potassium), wastes of metabolism (urea) and many toxins and drugs (penicillin). Achieved by 1200ml blood flowing through kidneys per minute, average person excretes 800-2000ml urine a day

Question 3

What is urine?

Answer 3

Urine is produced from the blood, contains waste products that the body wants to eliminate. Contains water, salts, urea, metabolites, hormones and small proteins. pH is around 4.6-8 (not tightly regulated) and is influenced by what is excreted

Question 4

How is urine useful?

Answer 4

Useful as we can see what is going wrong in the body: abnormal urine could show large proteins (too big to be filtered, filtration barrier affected), RBC (too big to be filtered so should not turn up in urine) and glucose (filtered but completely reabsorbed)

Question 5

What does the urinary system need to be effective?

Answer 5

System to remove filtrate from body, protection of organs, kidneys need ability to communicate with relative parts of body, need to be able to adapt to meet the bodies changing needs (nervous and hormonal control)

Question 6

Where are the kidneys located?

Answer 6

Right kidney is below left kidney as liver is above it, right is closer to the vena cava, left is closer to aorta. On top of kidneys is the adrenal glands
Located between T12-L3 (12th thoracic and 3rd lumbar vertebrae), hilum of kidney is at the level of L1
Protected by the 11th and 12th ribs

Question 7

What is the function of the kidneys?

Answer 7

Kidneys allow us to get blood to site of filtration (nephron), allow blood to leave once filtered and allows a pathway for urine to be removed from the kidney, stored and excreted as well as reabsorbing substances needed

Question 8

Structure of the kidney

Answer 8

Kidneys are retroperitoneal - located on posterior abdominal wall, covered on anterior side by peritoneum, surrounded, supported and protected by fat
Over surface of kidney adhered strongly is a fibrous capsule providing support - holds kidney together, prevents rupture and any infection
Outside of the fibrous capsule is the perirenal fat capsule which protects kidneys
Renal fascia fuses with peritoneum anteriorly, posteriorly fuses with fascia of lumbar muscles

Question 9

What is the medulla and the cortex?

Answer 9

Underneath fibrous capsule is the cortex, deeper is the medulla (cortex on outside, medulla on middle)
Medulla is divided into pyramids, each medullary pyramid ends in a papilla
Cortex is a continuous layer, parts of it extend between the renal pyramids, renal columns
Lobe of a kidney is a renal pyramid + associated cortex, 5-11 lobes per kidney

Question 10

What is a kidney lobe?

Answer 10

One medullary pyramid
All cortex that surrounds it including renal columns
Made up of nephrons - tiny tubes that filter from blood and create urine (situated towards cortex or medulla)

Question 11

What is the pathway of urine?

Answer 11

Papilla drain into calyx which collect urine and drain into the renal pelvis which allows urine to leave through hilum via ureter
Papilla -> minor calyx -> major calyx -> renal pelvis -> ureter

Question 12

How is blood supplied to the kidney?

Answer 12

Urine is produced by filtering waste from blood into the nephron
Filtration occurs in the cortex of the kidney
Renal artery arises from the abdominal aorta which branches into arteries that get smaller until they reach cortex
Blood is filtered and veins return the filtered blood from the cortex to the renal vein which drains into the inferior vena cava

Question 13

How is blood transported towards the site of filtration?

Answer 13

Once blood is at the cortex the afferent arteriole carries blood towards site of filtration = glomerulus
Glomerulus is made of glomerular capillaries and is where filtration occurs, some fluid is lost, remaining blood leaves in efferent arteriole

Question 14

How is blood transported away from the site of filtration?

Answer 14

Efferent arteriole carries blood away from the glomerulus to the peritubular capillaries (secondary capillary network which wraps around nephron and supplies it with oxygen) which collects substances that are reabsorbed and carry blood to the veins

Question 15

How are nerves related to kidneys?

Answer 15

Innervation is from a network of autonomic nerves and ganglia called the renal plexus
Sympathetic nerves act to adjust diameter of renal arteriole (if your blood pressure increases need to constrict to limit amount of blood entering glomerulus) and thus regulate blood flow

Question 16

Blood supply into cortex pathway:

Answer 16

Abdominal aorta -> renal artery -> series of arteries -> afferent arteriole -> glomerular capillary

Question 17

Blood supply away from the cortex after being filtered:

Answer 17

Glomerular capillary -> efferent arteriole -> peritubular capillaries -> series of veins -> renal vein -> inferior vena cava