excretion

Question 1

define excretion

Answer 1

getting rid of the waste products of metabolism

Question 2

define endotherms and ectotherms

Answer 2

endotherms- generate their own heat from their metabolic reactions
ectotherms- gain or lose heat from external environment

Question 3

excretory organs and their products

Answer 3

lungs - co2 and water
kidney- urine( water salts and urea )
skin- water urea and salts in the form of sweat

Question 4

functions of the skin

Answer 4

1 protection- the epidermis prevents the entry of pathogens
2 excretion- sweat is released from sweat glands travels through the sweat ducts and is removed from the skin and waste is removed
3 sense organ- receptors in the dermis allow it to act as a sense organ. they detect pain pressure temperature
4 food store- fat in the adipose tissue acts as an energy reserve
5 vitamin D production- special cells called melanocytes produce melanin in the malignant layer to protect the skin against harmful UV rays. Melanin also helps to absorb calcium in the gut.

Question 5

vasodilation (too hot)

Answer 5

arterioles in the dermis widen to allow more blood into capillaries near the surface of the skin, lots of blood flows in and heat is lost from the surface of the skin.
sweat is produced in sweat glands travels through sweat ducts and evaporates having a cooling effect.

Question 6

vasoconstriction (too cold)

Answer 6

erector muscles contract forming goosebumps and hairs stand up - piloerection
warm air is trapped close to the skin by the hairs and this helps to reduce heat loss. blood vessels in the skin contract and it reduces heat loss through the skin

Question 7

what do the kidneys consist of

Answer 7

2 kidneys located just below the diaphragm in abdominal cavity
2 ureters
bladder
urethra

Question 8

filtration in kidneys

Answer 8

incoming blood is filtered in the cortex. results in small substances being forced out of the bloodstream and into the kidney

Question 9

reabsorption in kidney

Answer 9

some useful materials are reabsorbed back into the bloodstream occurs in cortex and medulla

Question 10

secretion in kidneys

Answer 10

some substances are secreted into the cortex
eg. hydrogen ions. by controlling hydrogen ions kidneys control pH.

Question 11

what forms urine

Answer 11

water 96%
nitrogenous waste (2.5% mostly urea)
salts (1.5%)
urea is produced in the liver when excess proteins are broken down- deamination

Question 12

functions of kidneys

Answer 12

1 excretion- remove waste from the blood and convert them to urine. urine is sent to the bladder to be excreted through the urethra
2 osmoregulation- kidneys control water content by varying the water content of blood
and control salt by varying the amount released in urine.
kidneys ensure blood plasma is in the same concentration as body cells and that cells don’t have problems with osmosis.
3 pH control- by producing urine that is more or less acidic