Chapter 10 - Removal Of Wastes Flashcards
(36 cards)
What is excretion?
Excretion is the is removal from the body of the wastes of metabolism
What is the excretory system?
The excretory system is a system of the body that remove wastes of metabolism and passes them to the exterior.
What are the four main organs in the body which are involved either in processing or excretion of wastes
- Lungs; are in the excretion of the carbon dioxide that is produced by all body cells during cellular respiration.
- Liver; has an important role in processing many substances so that they can be excreted.
- Skin; Sweat Glands; skin secretes sweat which is largely water for cooling. Sweat contains the by products of metabolism Eg salts, urea, lactic acid
- Kidneys; (principle organ) they are responsible for constant concentration of materials in the body fluids.
- Alimentary canal; passes out bike pigments from the breakdown of haemoglobin - small intestine - faeces
Explain what the liver does in terms of excretion.
Located in upper abdominal cavity and has different functions including the preparation of materials for excretion.
Liver is a main by product of breaking down PROTEINS in diet and in body (RBCs) through the Process of DEAMINATION.
Proteins are primarily ‘body builders’, so they make of the structural materials of cells.
But if there is enough carbs and fats in diet or fast is stored well enough in body then protein needs to be metabolised and gotten rid of.
Eg Small amounts of amino acids from broken down protein of worn down RBCs are lost from body via urine, skin , hair and fingernails.
What is deamination?
DEAMINATION is the removal of the amino group from the amino acid molecule.
What is urine?
Urine is the fluid produced by the kidneys that contains wastes and excess materials.
Explain the process of DEAMINATION
If other energy sources have been used up, the body is able to metabolise large amounts of protein.
To make use of this protein in this way, the amino group (NH2) must first be removed from the amino acids.
DEAMINATION occurs in the liver with aid of enzymes
Once the amino group has been removed it is converted by the liver cells to ammonia (NH3) and then finally to urea.
The urea is eliminated from the body through urine.
The remaining part of the amino acid is primarily made up of carbon and hydrogen, which is converted into a carbohydrate.
This carbohydrate can easily be broken down by the cells to realse energy, carbon dioxide and water.
What is the DEAMINATION equation?
Amino acid + oxygen —————> carbohydrate + ammonia
(Enzymes)
How does the liver get rid of ammonia
Ammonia is extremely soluble in water and is highly toxic to cells.
1/1000th of a milligram of aminos in a litre of blood is sufficient to kill a person.
*The liver rapidly converts ammonia to a less toxic molecule called UREA. Moderate amounts of urea is harmless to the body. Urea can be easily excreted by the kidneys and is eliminated from the body in urine. (Small amounts gets excreted from sweat glands).
THE PROCESS CAN BE EXPRESSED IN THIS WAY
energy + CO2 + ammonia (NH3) —> Urea + water
Other than DEAMINATION what does the liver do?
- detoxifies alcohol and many other drugs such as antibiotics
- deactivates hormones and converts them into a form that can be excreted by the kidneys
- haemoglobin from dead RBCs is broken down in the liver to produce bile pigments which are passed out with faeces.
What are the main functions of the skin?
- provide protective covering over the surface of the body
- regulate body temperature
- thermoregulation via vasodilation and vasoconstriction
- excrete of metabolic wastes
How is the skin an excretory organ?
- sweat glands are located in the lower layers of skin known as the dermis
- ducts carry the sweat to a hair follicle or the skin surface where it opens at a pore
- cells surrounding the glands are able to contract and squeeze the sweat to the skin surface.
- even when there is no visible perspiration on the skin, the sweat glands secrete 500ml of water per day.
- dissolved in the water are sodium chloride, lactic acid and urea which are excreted from the body
- some drugs are also excreted this way
What are the kidneys?
They kidneys are a pair of reddish brown organs located in the abdomen - approx 11cm
What is the urinary system?
The kidneys, the bladder and ass ousted ducts are often referred to as the URINARY SYSTEM.
It is a system of the body which produces, stores and eliminates urine, the fluid waste excreted by the kidneys. -
Is a osmoregulation system - where it maintains right amounts of H2O and dissolved substances in our body
What are the three layers of skin?
Outer = Epidermis - closely packed epithelial cells/ tissues
Inner = Dermis (connective tissue)
Subcutaneous layer
What does the liver do?
- Deamination
- Detoxification - alcohol, drugs, antibiotics
- Hormone removal - deactivates and converts to a form to Excrete
- Dead RBCs breakdown into bile
- Carbohydrate metabolism - excess glucose turned to Glycogen to storage or the way
- Lips metabolism; excess carbs turned into fats
- Heat production - produced most heat
- Production of bile
- Storage of Vitamins and minerals
- Synthesis of proteins
What is the renal cortex?
The renal cortex is the outer dark red portion of the kidney which contains bowman’s capsules (many b vessel)
What is the renal medulla?
Renal medulla is the inner most region, which holds renal pyramids (8-18), the loop of Henle (which is where the nephron dips down into medulla) and is pale pink in colour.
What is a renal pelvis?
The renal pelvis is the inner layer which is cream in colour and collected urine from the collecting ducts (CD). There are three major calyces before it goes to the bladder.
It acts like a funnel for urine to flow into ureter.
What is a nephron
A nephron is a microscopic structure and the functional unit of a kidney.
A nephron = glomerular capsule + renal tubule (5cm) + associated blood supply
1 million nephrons in kidney
What are the three main stages for urine formation
- Glomerular filtration
- selective reabsorption
- tubular secretion
Explain the process of Glomerular Filtration (passive)
- first step of making urine and takes place in the renal corpuscle when fluid is forced out of the blood and is collected by the glomerular capsule
- one layer of glomerulus makes up the capillary wall and the other is the wall of the capsule.
- there is high blood pressure in G.C because the afferent arteriole leading into the glomerulus is wider in diameter than the efferent arteriole leaving it (resistant to blood flow )
- there is high BP is small ions (Na, Cl), Glucose, AA’s, water can be forced through differentially permeable capillary wall and to Bowman’s capsule space.
- result = Filtrate
- large molecules (RBC’s, large proteins) remain in capillaries because they cannot pass through the membrane
Filtrate consists of H2O, salts, AAs, fatty acids, glucose, urea, uric acid, creatinine, hormones, toxins and ions.
20% of plasma present is filtered through capillary wall into G capsule.
1% of 180L of filtration from kidneys is left as urine, the rest is reabsobed into blood.
Explain the process of selective reabsorption (passive osmosis and active transport occurs)
It is the second step in making urine as many components that are filtered from the capillaries of the glomerulus are of use to the body and their excretion would be undesirable.
- cells line in the renal tubule which reabsorb needed materials such as
- water, glucose, AA’s, Na, K, Ca, Cl, CO3-
- some wastes such as urea are partially absorbed.
- this process is taken place in a large surface area for effective reabsorption of materials.
- through long length of kidney tubule - 2 sets of convolutions tubules and loop of Henle.
- the active process of called Facultative Reabsorption occurs here under hormone control, for the regulation of amount of water that needs to be absorbed for body needs.
Explain the process of tubular secretion
Tubular secretion is the third process of urine formation where it adds materials to filtrate from the blood. Eg K, H, Creatinine and drugs such as penicillin.
- can be active or passive and has two main effects.
- removes certain unwanted materials from the body, and so controls the blood pH of 7.4.7.5.
To raise blood ph the tubules secret H+ and NH4 into filtrate.
These two substances make urine slightly acidic with normal ph of 6
Water and other substances not reabsorbed by drain from the collecting ducts to renal pelvis.
Once content is at pelvis and from pelvis it is called URINE.
It drains out into ureters and is pushed away in waves of muscle contraction to urinary bladder where it is stored.
Ureters = 25-30cm and the bladder is a hollow muscular organ from which urethra exists. Urethra carries urine from the bladder to the exterior of the body.
