Chapter 10- Removal Of Waste

Question 1

Excretion

Answer 1

Removal of the wastes of metabolism from the body

Question 2

What organs are involved in excretion for either processing wastes or the excretion of the wastes

Answer 2

Lungs
Liver
Sweat glands
Kidneys
Alimentary canal.

Question 3

Liver

Answer 3

. Located in upper abdominal cavity
. Prepares materials for secretion
. Proteins are primarily body builders that make up the structural materials of cells
. As long as the body has sufficient supply of fats and carbohydrates then little protein is used in energy releasing reactions
. Excess proteins from the diet cannot be stored in the cells so processes are required to remove it from the body
. Most protein is broken down in the body but the breakdown is mostly incomplete
. Liver detoxifies alcohol and many drugs
. Deactivates many hormones and converts them into a dorm that can be excreted by the kidneys
. Haemoglobin from red blood cells is is broken down in the liver to produce bile which are then passed out through the body with the faeces

Question 4

Amino acids breakdown in the liver

Answer 4

. Red blood cells are a source of protein and they are broken down into the constituent amino acid, some of these proteins are then made to make new proteins
. A small amount of amino acid is lost from the body through the urine, skin, hair and fingernails
. Proteins which have been built up from amino acids become the primary constituents of cell structures, enzymes, antibodies, and many glandular secretions
. If other energy sources have been used up, the body is able to metabolise large amounts of proteins.

Question 5

Deamination in liver

Answer 5

. To make use of proteins for an energy source the amino group (NH2) must be removed from amino acids
. Occurs in the liver with the aid of enzymes
. Once the amino group has been removed its is converted by the liver cells to ammonia (NH3) and then finally to urea
. Urea is eliminated in the body through the urine
. The remaining part of the amino acid which is mainly made up of carbon and hydrogen is converted into a carbohydrate this carbohydrate is readily broken down by the cells to release energy, carbon dioxide and water

Question 6

Ammonia in liver

Answer 6

. Extremely soluble in water and highly toxic to cells
. Cells of the liver rapidly convert ammonia to urea
. Moderate amounts of urea are harmful to the body
. Urea is easily excreted by the kidneys and is eliminated through the body as urine
. Small amounts of urea are lost as sweat from sweat glands

Question 7

The skin functions

Answer 7

. Provides a protective layer covering the surface of the body
. Regulates body temperature
. Has an important role in excretion

Question 8

Excretion from the skin

Answer 8

. Sweat glands secrete about 500mL of water each day
. Dissolved in the water is sodium chloride, lactic acid and urea
. Some drugs are also secreted by the skin

Question 9

Where are the sweat glands in the skin located

Answer 9

. Lower layers of the skin
. Sweat gland is a duct that carries the sweat to a hair follicle or to the skin surface where it opens into a pore
. Cells surrounding the sweat gland are able to contract and squeeze the sweat to the skin surface

Question 10

The kidneys

Answer 10

. Reddish brownish
. Located in the abdomen
. Kidney, bladder and their associated ducts are often referred to as the urinary system

Question 11

Microscopic structure of a kidney

Answer 11

. When seen under a microscope the kidney is seen to be composed of a large number of nephrons and collecting ducts

Question 12

What is a nephron

Answer 12

. The functional unit of the kidney where the urine is formed
. Each nephron is surrounded by a network of blood capillaries

Question 13

The way in which substances travel through a nephron

Answer 13

. Each nephron consists of a renal corpuscle and a renal tubule
. Nephron begins with an expanded end called the glomerular capsule and it looks like a double walled cup that surrounds and almost completely encloses a knot of arterial capillaries called the glomerulus
. Leading away from the glomerular capsule is the renal tubule and it begins withs winded section called the proximal convoluted tubule
. After eh proximal convoluted tubule there is a descending limb which then leads to the loop of henle
. After the loop of henle there is an ascending limb and the then tube coils and winds again and that is the distal convoluted tubule

Question 14

What happens after the distal convoluted tubule

Answer 14

The distal convoluted tubule of many nephrons join up into a collecting duct which opens into a chamber in the kidney called the renel pelvis
The renel pelvis is shaped like a funnel and it channels fluid from the collecting ducts and into the ureter

Question 15

What are nephrons of the kidney responsible for

Answer 15

. Removing wastes from the blood

. Regulating blood composition

Question 16

How are the kidneys able to carry out their function

Answer 16

. Well supplied with blood vessels

Question 17

How does blood flow through the kidneys

Answer 17

. The nephrons are well supplied with blood vessels
. Blood enters the kidneys through the renal arteries ams these arteries a quite large so the kidneys receive a lot of blood
. The renal artery divides into small arteries and arterioles
. Each renal corpuscle is supplied by an arteriole which is the afferent arteriole which then forms a knot of capillaries called the glomerulus which is located within the glomerular capsule
. The capillaries then unite to form another arteriole called the efferent arteriole which then passes out the renal corpuscle
. Efferent arteriole breaks up into a second capillary network that surround the proximal and distal convoluted tubules, the ascending snd descending limbs and the loop of henle which is called the peritubular capillaries
. Venous blood eventually drains away from this newtwork and leaves through the renal vein

Question 18

What three major processes does urine formation involve

Answer 18

. Glomerular filtration
. Selective reabsorption
. Secretion by the tubules

Question 19

Glomerular filtation

Answer 19

. Takes place in the renal corpuscle where fluid is forced out of the blood and is collected by the glomerular capsule
. Achieved by high blood pressure in the capillaries
. The afferent arterioles leading into the glomerulus has a wider diameter than the efferent arteriole leaving it and this narrowing increases resistance of flow of blood and produces a higher pressure in the glomerulus
. The pressure outside the capillaries in the glomerular capsule is negligible and the blood in the capillaries is separated from the capsule by only two layers of thin flat cells—— one which makes up the capillary wall and one that makes up the wall of the capsule
. When blood enters the glomerulus, the high pressure forces water and dissolved blood components through the membrane and into the capsule, the resultant fluid is called the filtrate

Question 20

Filtrate from glomerular filtration

Answer 20

. The resultant material from water and dissolved blood components from the blood in the capillary moving to the glomerulus capsule

Question 21

What does the filtrate consist of from glomerular filtration

Answer 21

. In a healthy person it consists of materials in the blood except for red and white blood cells and plasma proteins these are not in the filtrate because they are too large to pass through the differentially permeable membrane
. Water, salts, amino acids, fatty acids, glucose, urea, uric acid, creatinine, hormones, toxins and various ions

Question 22

Selective reabsorption

Answer 22

. Many of the things filtered from the capillaries to the glomerular capsule can be of use to the body so excretion of these things would be undesirable
. Therefore some selective reabsorption of filtrate must take place
. Process is carried put by cells that line the renal tube
. Materials that are reabsorbed include water, glucose, amino acids, ions (such as sodium, potassium, calcium, chloride and bicarbonate) some wastes like urea are partially absorbed as well and they are all returned to the blood

Question 23

What is needed for appropriate selective reabsorption

Answer 23

. Large surface area that is achieved by the long length of the renal tubule, two sets of convolutions and the loop of henle, and a huge number of nephrons in each kidney

Question 24

Reabsorption of water in selective reabsorption (facultative reabsorption)

Answer 24

. Absorption of water can be regulated depending on the body’s water requirements,
. The regulation of water can be controlled by the permeability of the plasma membranes of the cells making up parts of the tubules can be changed
. This is an active process under hormone control and is referred to as facultative reabsorption

Question 25

Tubular secretion

Answer 25

. Adds materials to the filtrate from the blood
. Materials secreted in this way are potassium, hydrogen ions, creatinine and drugs such as penicillin
. Can be either active or passive and has two main effects

Question 26

Main effects of tubular secretion

Answer 26

. Removes certain unwanted materials from the body

. Controls PH of the blood

Question 27

Tubular secretion in controlling the PH of the blood

Answer 27

. Body has to maintain bloods PH level between 7.4-7.5
. Our diet consist of many food that lower the PH , so to raise the PH of the blood the tubules secrete hydrogen and ammonium ions into the filtrate and these two substances make the urine slightly acidic with a normal PH of 6

Question 28

What happens to the substances that don’t get reabsorbed

Answer 28

. Drain from the collecting duct and into the renal pelvis
. From the pelvis the now called urine drains into the ureters and is pushed by waves of muscle contraction into the bladder where it is stored
. The two ureters, one from each kidney, are extensions of the pelvis of the kidneys and they extend 20-30cm to the urinary bladder
. The bladder is a hollow muscular organ from which the urethra exists and the urethra carries urine from the bladder to the exterior of the body

Question 29

how is the structure of the kidney related to its function of excretion of waste and regulation of water content of the body

Answer 29

. The glomerular capsule surrounds the glomerulus to collect fluid filtered out of the blood capillaries
. The arteriole leading out of the glomerulus has a smaller diameter than the arteriole leading in which raises the blood pressure so that more fluid is filtered out of the blood
. The tubule has two sets of convolutions and a long loop so that each tubule has a large surface area for reabsorption and secretion
. Each kidney has over a million nephrons so the total surface area available for reabsorption and secretion is extremely large

Question 30

Urine composition

Answer 30

. Body must excrete its wastes products on a regular basis (urea, sulphates and phosphates)
. These substances have to be in solution, and so the elimination of these wastes require a certain amount of water loss
. Regardless of the amount of water the body has, half a litre of water a day must be lost to remove wastes
. When water content is low the urine is very concentrated

Question 31

Urine composition under normal circumstances

Answer 31

. 99% of the water the enters the nephrons is reabsorbed
. The urine does not normally contain significant amount of proteins
. Urine does not normally contain any glucose
. The main materials making up the urine besides water are urea, ions, uric acid and creatinine

Question 32

Uric acid

Answer 32

. Produced by the metabolism is purines
. Purines may come from the breakdown of nucleic acids when cells die
. Purines occur naturally in many foods

Question 33

Creatinine

Answer 33

. Produces in muscle from the breakdown of creatinine phosphate which is an energy rich molecule

Question 34

How much urine should a healthy adult pass each day

Answer 34

1.5 litres
. Varies on diet and other factors
. Amber colour of urine is due to bile pigments

Question 35

Kidney stones

Answer 35

. Formed from solid crystals that build up inside the kidneys
. Form when urine becomes to concentrated
. Caused by insufficient fluids in the diet
. If crystals are small enough they can pass out of the body without harm and without being noticed
. Crystals may combine to form stones and larger stones may get stuck in the ureter, bladder or urethra which causes intense pain

Question 36

Kidney failure

Answer 36

. Kidney failure is where kidneys lose their ability to excrete waste and control the level of fluid in the body
. Most kidney diseases affect the glomerulus which reduces their ability to filter blood
. Proteins and sometimes red blood cells may filter through the glomerulus and be present in the urine
. If excessive proteins are lost in the urine, blood protein levels fall and fluid will accumulate in the tissues which causes swelling in the hands, feet face or other areas

Question 37

What lifestyle measures can you take to maintain a healthy kidney

Answer 37

. Regulate your diet to maintain a healthy weight
. Do not smoke
. Drink water instead if drinks that contain sugar
.drink alcohol in moderation
. Do not use performance enhancing drugs

Question 38

Dialysis

Answer 38

. This is method of removing waste from the blood when kidney failure occurs
. There are two types of dialysis peritoneal dialysis and haemodialysis

Question 39

What is the peritoneum

Answer 39

It’s a membrane that lines inside of the abdominal cavity and covers the abdominal organs such as the stomach liver and intestine
. It also has a very rich blood supply

Question 40

Peritoneal dialysis

Answer 40

. Occurs inside the body using the peritoneum as a membrane across which wastes can be removed
. A tube called the catheter is placed through the wall of the abdomen
. For an adult 2-3 L of fluid is passed through the catheter into the abdominal cavity
. The fluid contains glucose and other substances at concentrations similar to those found in the blood however there are no wastes in the fluid
. This means that because of the concentration difference wastes will diffuse out of the blood into the fluid in the abdominal cavity
. Useful substances stay in the blood because there is no concentration difference between the blood and the fluid
. After a time the fluid that was placed in the abdominal cavity is drained out through the catheter along with any wastes wastes and extra water that have diffused from the blood
. Peritoneal dialysis is usually completed each day

Question 41

haemodialysis

Answer 41

. Involves passing the blood through an artificial kidney or dialysis machine
. The blood passes through thousands of fine tubes made of a deferentially permeable membrane and immersed in a bath of fluid
. The concentration of substances in the fluid are similar to those in the blood except the fluid has no waste
. Because of the concentration differences wastes can diffuse from the blood and into the fluid
. Patience spend about 4-5 hours attached to the machine and dialysis is normally done three times per week