Excretion Flashcards
1
Q
osmoregulation
A
process by which animals solute concentration and balance water gain and loss
2
Q
Why is maintaining the fluid environment important in the body?
A
It supports the proper function of cells, tissues, and organs.
3
Q
What must be kept within narrow limits during osmoregulation?
A
The relative concentrations of water and solutes.
4
Q
Why must ion concentrations be tightly regulated in the body?
A
To allow normal activity of muscles, neurons, and other body cells.
5
Q
What is osmoregulation based on?
A
The controlled movement of solutes between internal fluids and the external environment.
6
Q
osmosis
A
water enters and leaves cells
7
Q
osmolarity
A
unit of measurement is solute concentration (moles solute/L)
8
Q
Osmoconformer
A
- to be isoosmotic with its surrounding - internal osmolarity is equal to the environment around them
- mostly marine animals
- stable environment
9
Q
osmoregulator
A
- to regulate internal osmolarity independent of external environment
- marine, fresh water and land
- changeable environment
10
Q
energetics of osmoregulation
A
- maintaining osmolarity requires energy
- energy expended to maintain osmotic gradients that cause water to move in or out
- the energy cost depends on - the surroundings, movement of water on the surface, pumping mechanism
- the energy cost is minimized by having body fluids that are adapted to the salinity of the animals habitat
11
Q
waste
A
- metabolic wastes must be dissolved in water to be excreted from the body
- the type and quantity may have a large impact on water balance
- breakdown of nitrogenous compounds release ammonia
- process that rids the body of nitrogenous metabolites
- osmoregulation and excretion are structurally and functionally linked
12
Q
ammonia - nitrogenous waste
A
- animals that excrete nitrogenous wastes as ammonia need access to lots of water
- ammonia is released across the whole body surface
13
Q
urea - nitrogenous waste
A
- ammonia excretion is less suitable for land animals
- no access to sufficient water to excrete ammonia
- produced in the liver, product of the ornithine cycle
- urea has very low toxicity and can be transported in the circulatory system
- energetically expensive
14
Q
uric acid - nitrogenous waste
A
- birds, insects and many reptiles
- relatively non-toxic and not readily dissolvable in water
- more energetically expensive to produce than urea
15
Q
liver
A
- after the skin, the liver and the brain are the largest organs in the body
- average weight of 1.3 kg
- the only human organ that is capable of natural regeneration
- the liver performs many metabolic and homeostatic functions
16
Q
the liver - key functions
A
- important filtering mechanisms for the circulation by removing foreign particulate
- synthesis and secretion of bile
- carbohydrate, protein and fat metabolism
- endocrine function
- iron and copper storage
- vitamin A,B12, D, E, K storage
- detoxification
17
Q
amino acid catabolism
A
- the breakdown of amino acids occur by transamination and deamination
- the by product of this reaction (NH₄+) will be detoxified in a series of reaction known as the urea cycle
18
Q
detoxification - ornithine cycle
A
- ammonia is very toxic to body tissues
- ammonia released during deamination is rapidly removed by the liver and converted to urea
- all urea is synthesised by the liver and excreted by the kidneys
- some diffuses into the intestine - converted to ammonia by enteric bacteria
19
Q
detoxification - drugs and protein
A
- substances that are not normally present in the body are known as xenobiotics
- liver is responsible for neutralizing xenobiotics - modifying chemical constitution (biotransformation)
- the liver also plays an important role in inactivation and excretion of hormones such as steroids
20
Q
metabolism in alcohols
A
- alcohols is readily absorbed from the gastrointestinal tract
- transported to the liver via the hepatic portal vein
- alcohol metabolism proceeds by two major pathways:
- alcohol dehydrogenase (ADH) system
- microsomal ethanol oxidising system (MEOS)
- catalase pathway (minor pathway)
21
Q
The kidney - excretory process
A
- central to homeostasis - dispose metabolic waste and control fluid composition
- diverse excretory systems are variations on a tubular theme
- the involves four key processes - filtration, reabsorption, secretion and excretion
- animals produce fluid waste called urine
- functions in both osmoregulation and excretion
22
Q
Nephron
A
- functional unit of the vertebrate kidney
- each nephron is made up of several components
- glomerulus
- Bowmans capsule
- proximal tube
- loop of Henle
- distal tube
- collecting duct
23
Q
Bowman’s capsule
A
- porous capillaries and specialised cells of bowman’s capsule are permeable to water and small solutes, but not blood cells or larger molecules
- high hydrostatic pressure forces small molecules from the blood across the Bowmans capsule and into the renal tubules
24
Q
Adaptations of the glomerulus
A
- larger diameter of the afferent arteriole than the efferent arteriole causes an increase in blood pressure
- gaps between epithelial cells allow molecules to leave the blood
- basement membrane acts as a filter only allowing small molecules through and retains protein and blood cells
- filtrate produced contains water, salts, glucose, amino acids, vitamins, nitrogenous waste and other smaller molecules
25
the proximal tube
reabsorption - Na+, Cl-, HCO₃- , K+, H₂O, glucose, amino acids
- secretion - H+, ammonia, organic acids and bases
- reabsorption is critical for the recapture of ions, water and valuable nutrients
- maintaining pH balance
- some toxic materials are actively secreted into the filtrate
26
loop of Henle - descending limb
- Reabsorbs water (H₂O) through aquaporin proteins.
- Permeable to water, but not to ions.
- Water moves out because the interstitial fluid is hyperosmotic (osmolarity increases from cortex to medulla).
- Osmolarity of filtrate increases as it descends (300 → 1200 mOsm).
27
Loop of Henle - ascending limb
- Impermeable to water (no aquaporins).
- Reabsorbs ions like Na⁺, Cl⁻, K⁺, Ca²⁺, HCO₃⁻, Mg²⁺.
- Ions are actively transported out, decreasing the filtrate's osmolarity (100 mOsm as it exits).
- H⁺ is secreted into the filtrate.
- Two segments:
- Thin segment: passive ion movement.
- Thick segment: active ion transport.
28
The distal tube
- regulating K+ and NaCI concentration of body fluids
- maintaining pH balance
- late distal tube - secretion - K+, H+
- early distal tube - reabsorption - Na⁺, Cl⁻, K⁺, Ca++, HCO₃⁻, Mg++.
29
the collecting duct
- carries filtrate through medulla to the renal pelvis
- formation of urine
- reabsorption of water and nearly all sugars, amino acids and vitamins
- REABSORPTION
Na+, Cl-, K+, HCO₃-, H₂O
- SECRETION
K+, H+
30
Solute gradients
- the mammalian kidney's ability to conserve water is key to terrestrial adaptation
- a considerable energy is expanded for the active transport of solutes against concentration gradients to produce hyperosmotic urine
- primary solutes affecting osmolarity:
- Sodium chloride (NaCl) is deposited into the medulla by the loop of Henle, while urea is deposited into the medulla by the collecting duct
31
counter current multiplier system
- Process of using energy to generate an osmotic gradient to enable the
reabsorption of water from the filtrate (or tubular fluid) and produce concentrated urine
- The transport of NaCl from the ascending limb (passive/active) will result in the passive movement of water out of the filtrate (or tubular fluid) in the descending limb and into the interstitial space
▪ Expand energy to create concentration gradient
▪ For its size, the kidney has one of the highest metabolic rates of any organ
32
adaptations of the kidney
- Variations in nephron structure and function equip kidneys for osmoregulation in their various habitats
- The length of the loop of Henle is positively correlated with the need for water conservation in animals
33
Homeostatic regulation
- Volume and osmolarity of urine are adjusted according to an animal’s water and salt balance and its rate of urea production
- A combination of nervous and hormonal control manage the osmoregulatory function of the kidney
34
Antidiuretic hormone (ADH)
- also called vasopressin
- produced by the hypothalamus and stored in the pituitary gland
- osmoreceptor cells monitors the osmolarity of blood, regulate the release of ADH
- influences water uptake by initiating a temporary increase in the number of aquaporins in the membranes of collecting duct cells
