chapter 11: excretion in humans Flashcards
What are catabolic reactions?
and example
- chemical reaction in which complex substances are broken down into simpler ones
- eg. Glucose ( complex) is oxidases or broken down into carbon dioxide and water (simple) with the release of energy during cellular respiration
What are anabolic reactions?
- chemical reactions in which simple substances are built into more complex substances
- eg. The formation of proteins from amino acids
What is excretion ?
The process by which metabolic waste products and toxic substances are removed from the body of an organism
Metabolic waste produc s and toxic substances
> excretory products
- most unicellular organisms such as amoeba are able to excrete their waste products by diffusion into the surrounding env
- larger organisms, especially animals with impermeable skin, need special excretory organs
What is the structure and the function of the urethra?
(urinary system)
- it’s is the duct through which urine passes from the bladder to the outside of the body
What is the function of the sphincter muscle?
(urinary system)
- it is located at the bottom of the bladder
> used to control urination - when the bladder is full, sensory neurones send nerve impulses to the brain
-to urinate, brain sends nerve impulses to the sphincter muscle to cause it to relax - urine is then able to flow into the urethra and out of the body
What is the structure and the function of the urinary bladder?
(urinary system)
- the urinary bladder is an elastic muscular bag located in front of the rectum
> stores urine
What is the structure and function of the ureter?
(urinary system)
- a narrow tube that connects the kidney to the urinary bladder
- urine from each kidney passes through the ureter to the urinary bladder
What is the hilus?
(urinary system)
- the surface of the kidney that faces the vertebral column is concave
- at the centre of this concave surface is a depression called the hilus
- the renal artery and the renal vein and the nerves are connected to the kidney at the hilus
( structure of kidney)
What is the cortex?
- the outer red region
- it is covered and protected by a fibrous capsule
( structure of kidney)
What is the medulla?
- the medulla is the inner pale red region
- the renal pyramids are located in this region
( structure of kidney)
What is the structure and function of renal pyramid?
- renal pyramids are conical structures located in the medulla
- the human kidney contains 12-16 pyramids
- the radial stripes on the medulla pyramids indicate numerous kidney tubules
> nephrons - urine is formed in the nephrons
( structure of kidney)
What is the renal pelvis?
- the renal pyramids project into a funnel like space called the renal pelvis
- the renal pelvis is the enlarged portion of the ureter inside the kidney
( structure of a nephron)
what is the bowmans capsule?
- nephron begins in the cortex
> as a cup-like structure called the bowman’s capsule
( structure of a nephron)
what is the proximal convoluted tubule?
- capsule leads into a short, convoluted tubule
> ( straightens out as it passes into the medulla)\ - the convoluted part is the PCT
( structure of a nephron)
what is the loop of Henle?
- in the medulla, the tubule extends into the renal pyramid and makes a uturn back into the cortex
- u-shaped portion
( structure of a nephron)
what is the distal convoluted tubule?
- when the tubule enters the cortex again
( structure of a nephron)
what is the collecting duct?
- the tubule opens into the collecting duct
> runs straight through the medulla and eventually opens into the renal pelvis
describe blood entering the kidney
-blood enters the kidney by the renal artery which branches out into arterioles
-arterioles further branches into a mass of blood capillaries in the bowman’s capsule (glomerulus)
- the bowman’s capsule with the glomerulus is called the renal corpuscle
- blood leaving the glomerulus enters blood capillaries surrounding the nephron
- blood capillaries unite to form venules which in turn join to form a branch of renal vein
describe the process of ultrafiltration
- blood flows from the branches of renal artery into the glomeruli in the renal corpuscles
> most blood plasma is force out of the glomerular blood capillaries into the bowman’s capsule - caused by the high hydrostatic blood pressure
> the AFFERENT arteriole that brings blood into the glomerulus is wider (diameter) than the EFFERENT arteriole which carries blood away - this creates a high blood pressure in the glomerulus which provides the main force required for the filtration process
- the PPM that wraps the glomerular blood capillaries is a very fine filter
> BASEMENT MEMBRANE
> has very small pores that allow only water and very small molecules to pass through
describe selective reabsorption.
- at the PROXIMAL CONVOLUTED TUBULE
> most mineral salts and all glucose and amino acids (in a healthy person) are adsorbed through the walls of the tubule into the surrounding the blood capillaries
- solutes absorbed via diffusion and active transport
> reabsorption is highly selective
> only absorb substances required by the body
- most of the water is also absorbed by osmosis here - LOOP OF HENLE
> some water is reabsorbed - DISTAL CONVOLUTED TUBULE
> some water and mineral salts are absorbed - THE COLLECTING DUCT
> some water is reabsorbed
> excess water, excess salts and metabolic waster products: ( urea, uric acid and creatine) pass out of the collecting duct into the renal pelvis as a mixture called urine
( composition of urine)
what will a protein rich diet affect the urine produced?
- more urea present in the urine
> urea is formed when excess amino acids are deaminated
just read :)
a patient with diabetes excretes large amount of glucose in their urine
- they are unable to store up excess glucose as glycogen
> high concentration of glucose in the blood
> glucose is filtered of the glomerulus to form part of the glomerular filtrate
> nephrons are unable to reabsorb all the glucose fast enough
> large amount of glucose in urine
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what is the definition of osmoregulation?
the control of water and solute concentrations in the blood to maintain a constant water potential in the body
what is osmoregulation and what is it controlled by?
- water potential of the blood in the body has to be kept constant
> drastic changes in the water potential of the blood can result in serious problems
eg. when the blood plasma is too diluted
> water enters blood cells by osmosis
> blood cell will swell and burst
- tissue cells will also swell
eg. when the blood plasma is too concentrated,
> water moves out the cells by osmosis
> blood cells and tissue cells will become dehydrated and shrink
> make them unable to carry out their metabolic functions properly > may be fatal
- water potential of the blood depends on the amount of water and mineral salts in the blood plasma
- the amount of water is controlled by antidiuretic hormones (ADH)
>produced by the HYPOTHALAMUS (region of the brain)
> released by the PITUITARY GLANDS
> increases the water reabsorption at the nephrons
(osmoregulation)
what happens when there is a loss of water from the body?
- the water potential in blood decreases
> stimulates the hypothalamus in the brain
> the pituitary gland releases more ADH into the bloodstream - cells in the walls of the collecting ducts become more permeable to water
> more water reabsorbed from the collecting duct into the blood capillaries - smaller amount od urine is produced
> urine is more concentrated
> water potential of blood returns to normal
(osmoregulation)
what happens when there is a large intake of water?
- the water potential in blood increases
> stimulates the hypothalamus in the brain to release less ADH into bloodstream - cells in the walls of collecting duct become less permeable to water
> less water reabsorbed from collecting duct into capillaries - larger volume of urine produced
> urine produced more diluted
> water potential of blood returns to normal
how does water potential of blood relate to blood pressure?
- the amount of water reabsorbed affects the blood volume
>which affects the blood pressure - the higher the blood volume, the higher the blood pressure
how do doctors prevent people from having a stroke because of high blood pressure?
- prescribe drugs called diuretics
> reduce the production of ADH - a large amount of dilute urine is produced and the volume of water in the blood is decreased
> lowering the blood pressure
what are the common causes of kidney failure?
- high blood pressure
-diabetes - alcohol abuse
- severe accidents that physically damage the kidney
- complications from undergoing major surgery
what happens when the kidneys fail?
- if one fails > still can lead normal life
- if both fails, person will die unless prompt medical treatment is given
- a person with kidney failure can get a kidney transplant
-if donor kidney not available, they can be treated with dialysis using a dialysis machine
> dialysis machine mimics the function of a kidney
> cleans the patients blood from metabolic waste and toxins - for effective treatment,
patient needs to undergo dialysis 2-3 times a wweek - each session is about 3-5 hours
how does a dialysis machine work?
- blood is drawn from the vein in patient’s arm
> and is pumped through the tubing in the dialysis machine - tubing is bathed in a specially controlled dialysis fluid
- walls of the tubing in the machine is partially permeable - small molecules like urea and other metabolic waste products, diffuse out of the tubing into the dialysis fluid
> blood cells, platelets and large molecules remain in the tubing - the filtered blood is then returned to a vein in the patient’s arm
(features of a dialysis machine)
why does the dialysis fluid have the same concentration of essential substances as healthy blood?
- ensures that essential substances (glucose, amino acids and mineral salts)
> do not diffuse out of the blood into the dialysis fluid
> + is patients blood lacks these essential substances
> they will diffuse from the fluid into the blood
(features of a dialysis machine)
why does the fluid not contain metabolic waste products?
- this sets up a concentration gradient that allows waste products
>(urea, uric acid, creatine, and excess water and mineral salts)
> to diffuse out of the tubing into the dialysis fluid
>waste products removed from the blood
> maintains the correct solute composition and water potential of the blood
(features of a dialysis machine)
why does the tubing have to be narrow long and coiled?
- increases SA/V ratio which helps speed up the rate of exchange of substances between the patient’s blood and the dialysis fluid
(features of a dialysis machine)
why is the direction of the blood flow opposite to the flow of the dialysis fluid?
- maintains a concentration gradient for the removal of waste products
