Lecture 28 - Urinary system I, An overview and gross structure of the kidney

Question 1

What is the role of the urinary system?

Answer 1

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

Question 2

Cortex

Answer 2

Cortex is the outermost or superficial layer of an organ

Question 3

Medulla

Answer 3

A medulla is the middle of something

Question 4

Hilum

Answer 4

A depression or fissure where structures such as blood vessels and nerves enter an organ

Question 5

How does the urinary system maintain balance?

Answer 5

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 800-2000 ml urine/day

Question 6

What is urine?

Answer 6

Waste product excreted to maintain balance within the body

Normal urine:
Water 
Salts 
Urea
Metabolites, hormones and small proteins 

Urine pH is not tightly regulated (pH approx 4.6-8) and is influenced by what is excreted - everything that goes into the urine influences the pH range, this means that we know what we normally find in the urine and so we can use it as a diagnostic tool

Very noninvasive and easy test for diagnostics

Abnormal urine:
Large proteins (too big to be filtered)
RBC (too big to be filtered)
Glucose (filtered, but not completely reabsorbed)

Question 7

To be effective, the urinary system needs….

Answer 7

Delivery system for blood
Selective filtration system
Filtrate recovery mechanism - a system of bringing it back into the body
System to return recovered, filtered fluid to body
System to remove filtrate from the body
Protection - because it is a waste product and has stuff in it that we do not want in the body, it could damage us so we need protection
Ability to communicate with relevant parts of the body - so that we don’t loose to much of something that we want to keep
Adaptable to meet the body’s changing needs

Question 8

Main components of the urinary system

Answer 8

2 kidneys
2 ureters - thin tube coming out of the kidney and run down carrying urine and enter into the urinary bladder
Urinary bladder
Urethra - single tube that runs out of the urinary bladder and this is how we can excrete the urine

Question 9

The structure of the kidney allows

Answer 9

Blood to be brought into close proximity with the nephron, for filtering - the nephron is what filters selectively and absorbs what we want to keep
Blood that has been filtered to leave the kidney
A pathway for urine to be removed from the kidney, stored and then excreted
Protection

Question 10

The kidneys

Answer 10

Highest point of the kidneys is located at T12, L3 is the lowest point
11th and 12th ribs protect the kidneys, these are the floating ribs
Convex side faces laterally, concave notch faces medially
Medial surface has a concave notch called the hilum - renal blood vessels, lymphatics, nerves and the ureter are at the hilum

Left kidney is a little bit higher than the right and this is because in the right region there liver will be sitting on top of the kidney which will push it down that side a little bit

They sit at the bottom of the ribcage around the 11th and 12th rib

Reteroperitoneal = located on posterior abdominal wall, covered on anterior side of peritoneum
Surrounded, supported and protected by fat - fat is protective, insulting and supports the kidneys whilst also holding them in place

Question 11

Retroperitoneal

Answer 11

Reteroperitoneal = located on posterior abdominal wall, covered on anterior side of peritoneum

Question 12

Kidneys and relationship with major parts of the cardiac system

Answer 12

The left is closer to the aorta

The right is closer to the inferior vena cava

Question 13

Gross structure of the kidneys

Answer 13

Three regions - cortex, medulla and pelvis 
Fibrous capsule (thick adventitia layer to the kidney itself) 

Inner medulla
Divided into pyramids
Each medullary pyramid ends in a papilla

Outer cortex
Continuous layer
Renal columns

Cortex and medulla
Multiple functional lobes
5-11 lobes per kidney

Question 14

Kidney lobe

Answer 14

One medullary pyramid and all of the cortex that surrounds it (including the renal columns)

Made up largely of nephrons - tiny tubes that filter from blood and create urine

Question 15

Urine and the gross structure of the kidney

Answer 15

Urine drains from each papilla and collects in a calyx
Calyces join to form the renal pelxcis
Pelvis narrows as it exits the hilum to become the ureter

Urine travels into papilla => minor calyx => major calyx => renal pelvis => ureter

Question 16

Minor calyx and major calyx

Answer 16

The renal calyces are chambers of the kidney through which urine passes
The minor calyx surround the apex of the renal pyramids
Two or three minor calyx converge to form a major calyx, through which urine passes before continuing through the renal pelvis to the ureter

Question 17

Pyleogram

Answer 17

form of imaging of the renal pelvis and ureter

Ingest a contrast dye and have an X-ray done which will light up anywhere where there is urine present

Question 18

Name three structures that provide external protection for the kidneys

Answer 18

11th and 12th ribs
Renal fat pad
Fibrous capsule

Question 19

Blood supply to the kidney

Answer 19

Urine is produced by filtering waste from the blood into the nephron - need lots of blood vessels to do this and these blood vessels need to be very small because nephrons are tiny
Filtration occurs in the cortex of the kidney - there are not really any blood vessels going into the medulla because filtration occurs in the cortex
Renal artery arises from the abdominal aorta
Branching arteries get smaller and smaller until they reach the cortex
Blood is filtered
Veins return filtered blood from the cortex to the renal vein then to the inferior vena cava

The abdominal aorta carries oxygen rich blood from the heart and it is then going to branch and go to the abdominal organs and the renal system is one of those, so the renal artery branches away from the abdominal aorta and it is going to head in via the hilum and once it enters through the hilum it is going to branch again and it will branch into lots of littler arteries that head out to different regions in the kidney and these vessels will branch again and again and again and gets smaller and smaller as they do until we get out to the cortex which are the tiniest of the arteries and will then go into capillaries and then from the capillaries we will filter the blood and then once the blood is filtered it will be returned back so from these tiny little vessels coming together to form bigger vessels draining away from this region and getting bigger and bigger until we get to the renal vein which is going to empty out into the inferior vena cava which will carry the blood back to the heart

Question 20

What happens to blood in the cortex?

Answer 20

The afferent arteriole delivers blood from the arteries to the glomerulus
The glomerulus is made of glomerular capillaries and is where filtration occurs

The efferent arteriole carries blood from the glomerulus to the peritubular capillaries
The peritubular capillaries carry blood to the veins - these are for reabsorbing anything that we actually want to keep and put back into blood

We have arterioles on either side and because they can be constricted and dilated to change the flow of blood which means that we can control how much filtration is occurring

Question 21

Afferent arterioles

Answer 21

The afferent arteriole delivers blood from the arteries to the glomerulus
The glomerulus is made of glomerular capillaries and is where filtration occurs

Question 22

Efferent arterioles

Answer 22

The efferent arteriole carries blood from the glomerulus to the peritubular capillaries
The peritubular capillaries carry blood to the veins - these are for reabsorbing anything that we actually want to keep and put back into blood

Question 23

Flow of blood through the kidneys

Answer 23

Blood supply into the cortex to be filtered:
Abdominal aorta => renal artery (through hilum) => series of arteries => afferent arteriole =>glomerular capillary

Blood supply away from the cortex after being filtered:
Glomerular capillary => efferent arteriole =>peritubular capillaries => series of veins =>renal vein (through the hilum) => inferior vena cava

Question 24

Blood supply into the cortex to be filtered

Answer 24

Blood supply into the cortex to be filtered:

Abdominal aorta => renal artery (through hilum) => series of arteries => afferent arteriole =>glomerular capillary

Question 25

Blood supply away from the cortex after being filtered

Answer 25

Blood supply away from the cortex after being filtered:
Glomerular capillary => efferent arteriole =>peritubular capillaries => series of veins =>renal vein (through the hilum) => inferior vena cava

Question 26

Nerve supply

Answer 26

Innervation is from a network of autonomic nerves and ganglia called the renal plexus
Sympathetic nerves act to adjust the diameter of renal arterioles and thus regulate blood flow

Question 27

Introduction to the nephron

Answer 27

Microscopic functional unit of the kidney
Bulk of the kidney is made up of nephrons, apart from blood vessels
Filters blood
Selectively reabsorbs or secretes
Produces urine

1st part - renal corpuscle (contains efferent arteriole, afferent arteriole, glomerulus)
2nd part - PCT (proximal convoluted tube)
3rd part - Nephron loop
4th part - DCT (distal convoluted tube)
5th part - collecting duct

Question 28

Which kidney is the most inferior and why?

Answer 28

Right is lower due to the liver

Question 29

What structures comprise a kidney lobe?

Answer 29

Single medullary pyramid and cortex that surrounds it = lobe