Urinary System Flashcards
Function of the urinary system
To control the volume and composition of blood by removing excess fluid and waste products from the body.
Where are sites in which kidney stones appear ?
Uretropelvic junction
Crossing external iliac vessels
Structure of Urinary System
2 kidneys
2 ureters
Urinary bladder
Urethra
Location of Kidney
Located towards the upper back of the abdominal cavity. They are protected by the bottom of the rib cage and a layer of fat.
Functions of the kidneys
The kidneys filter the blood to produce urine.
Homeostasis
Hormone secretion - renin, erythropoietin
What happens in homeostasis ?
Removal of waste products
Regulation of water balance
Regulation of electrolyte balance, K+, Na+ and Ca+
What is homeostasis ?
In a state of homeostasis, body levels are constantly adjusting in response to changes outside and inside the body.
What hormones are secreted by the kidneys ?
Erythropoetin
Renin
Active form of vitamin D
Prostaglandins
Internal structure of kidney
Kidneys are covered by a fibrous capsule.
3 inner layers - renal cortex, renal medulla, renal pelvis
Renal medulla has a conical structure called medullary pyramids, which end in renal papilla.
The medullary pyramids are connected to minor calyces.
The minor calyces lead to major calyces.
The major calyces open into the renal pelvis.
The renal pelvis leads to the ureter.
How much cardiac output do the kidneys receive ?
20-25% of total Cardiac output
What happens after the kidneys filter the blood to produce urine ?
Once produced, urine will flow through the ureters into the bladder for storage, until its ready to be excreted through the urethra.
What is a nephron ?
The nephron is the basic functioning unit of the kidney.
Structure of nephron
Each nephron consists of a glomerulus and a series of complicated twisted tubules.
What is the glomerulus ?
A network of capillaries located within a structure called Bowman’s capsule.
What do kidneys need in order to filter the blood ?
A good blood supply
Function of the loop of Henle
The principal function of the loop of Henle is in the recovery of water and sodium chloride from urine.
This concentrates the urine.
Where are Bowman’s capsules located ?
Bowman’s capsule is located in the renal cortex, part of your kidney.
What 2 arteries supply blood to the kidneys ?
The left and right renal arteries, that branch directly off the aorta (the largest artery in the body)
Once inside the kidneys what do the left and right renal arteries branch into ?
Smaller and Smaller arteries and eventually give rise to the capillary within the glomerulus.
Feature of capillaries inside the Bowman’s capsule
They have tiny openings in them that let small molecules filter out of the blood.
Through this process, waste products are removed from the blood, whilst nutrients remain within the blood.
At the end of filtration, what are the 2 distinct liquids formed ?
Filtered blood (which remains in the capillaries)
Filtrate in the Bowman’s capsule, which forms the basis of urine
What happens as the filtrate leaves the Bowman’s capsule ?
It flows through the tubules that make up the rest of the nephron.
These tubules will reabsorb from of the substances that the body wants to keep, e.g. water, nutrients and minerals from the filtrate.
By the time the filtrate reaches the end of tubes, only excess fluid and waste products remain, called URINE.
What is the renal pelvis ?
The urine produced in each kidney is emptied into an area in the kidney called the renal pelvis.
After the urine collects in the renal pelvis, What happens ?
The urine flows through the ureters into the bladder.
Features of the ureters
Muscular tubes
Have smooth muscle in their walls
The muscle contracts the move urine form the kidney into the bladder.
What prevents the back flow of urine from the bladder ?
There is a small triangular fold which keeps the urine from flowing back into the ureters.
What is the function of the bladder ?
A reservoir for holding urine.
Kidneys never take a break, so urine is constantly produced and transported through the ureters into the bladder and stored, until urination occurs
What are the bladder and ureters lined with ?
A mucous membrane to protect it from infections.
When does urination occur ?
When the walls of the bladder contract.
What structure continues after the bladder ?
The urethra
What is the point where the bladder and urethra join called ?
The internal sphincter
Function of the internal sphincter
An involuntary muscle that keeps the bladder closed whilst the bladder fills with urine.
Function of the urethra
Carries urine from the bladder to the outside of the body
Where does the urethra start and end ?
Start - Below the internal sphincter
End - External urethral opening
External Sphincter
Ring of voluntary muscle that relaxes voluntarily to allow urine to pass during urination.
Difference in size of urethra in male and female
Male : 6-8 inches
Female : around 2 inches
High levels of sodium
More water will be retained
Loss of Sodium through vomiting/ diarrhoea
Can lead to dehydration
Importance of Potassium and Calcium
Maintains skeletal muscle function as well as cardiac muscle.
What happens if there is too much potassium in the body ?
This can affect the heart and lead to serious issues, even death.
Micturition
The action of urinating (voluntary)
Renal sinus
A compartment inside your kidney that uses fat to cushion important parts like the renal pelvis, lymphatic channels, calyces and renal artery
How is bladder emptying controlled ?
Emptying is prevented via the CNS until the outer sphincter is relaxed voluntarily.
