The Excretory System, Homeostasis and Osmoregulation Homeostasis Keeping the balance animal body needs to coordinate many systems all at once temperature blood sugar levels energy production
water balance & intracellular waste disposal nutrients ion balance cell growth maintaining a steady state condition Osmoregulation hypotonic Water balance freshwater hypotonic water flow into cells & salt loss saltwater hypertonic water loss from cells hypertonic land
dry environment need to conserve water may also need to conserve salt Why do all land animals have to conserve water? always lose water (breathing & waste) may lose life while searching for water Intracellular Waste What waste products? what do we digest our food into CO2 + H2O carbohydrates = CHO lots! CO2 + H2O lipids = CHO
CO2 + H2O + N proteins = CHON nucleic acids = CHOPN CO2 + H2O + P + N cellular digestion cellular waste NH2 = ammonia H| O || H NC COH | H R very
little CO2 + H2O Nitrogenous waste disposal Ammonia (NH3) very toxic carcinogenic very soluble easily crosses membranes must dilute it & get rid of it fast! How you get rid of nitrogenous wastes depends on who you are (evolutionary relationship) where you live (habitat) aquatic
terrestrial terrestrial egg layer Nitrogen waste Aquatic organisms can afford to lose water Ammonia: most toxic Terrestrial need to conserve
water Urea: less toxic Terrestrial egg layers need to conserve water need to protect embryo in egg uric acid: least toxic Kidney Structure & Function Excretion: the process of removing metabolic waste from the cells, tissue fluid, and blood of
living organisms The main organ of excretion in mammals is the kidney Osmoregulation: the control of water balance of the blood, tissue or cytoplasm of a living organism Kidney Structure & Function Functions: Produces urine Maintain water balance Maintain blood pH Maintain blood pressure
The functional unit of the kidney is the nephron There are more than 1 million nephrons in a human kidney On average 120mL/min of fluid passes through the kidney Kidney Structure & Function Roles of the nephron: Ultrafiltration Reabsorption Secretion For the kidney you should be able to label: Cortex
& artery epithelial cells Mammalian System Filter solutes out of blood & reabsorb H2O + desirable solutes Key functions blood filtrate Filtration: fluids (water & solutes) filtered out of blood Reabsorption: selectively reabsorb (diffusion) needed water + solutes back to blood Secretion: pump out any other
unwanted solutes to urine Excretion: expel concentrated urine (N waste + solutes + toxins) from body concentrated urine Afferent Efferent Nephron Functional units of kidney 1 million nephrons per kidney Function filter out urea & other solutes (salt, sugar) blood plasma filtered into nephron high pressure flow
selective reabsorption of valuable solutes & H2O back into bloodstream greater flexibility & control Mammalian kidney Interaction of circulatory & excretory systems Circulatory system glomerulus = ball of capillaries Excretory system nephron Bowmans capsule loop of Henle proximal tubule descending limb
H2O H2O H2O Na+ ClH2O Na+ ClH2O H2O Loop of Henle Collecting duct Nephron: Filtration Glomerulus: a ball of capillaries that are fenestrated (have pores) and are surrounded by a basement membrane that filters what passes through into the filtrate
filtered out of blood H2 O glucose salts / ions urea not filtered out cells proteins high blood pressure in kidneys force to push (filter) H22O & solutes out of blood vessel BIG problems when you start out
with high blood pressure in system hypertension = kidney damage Afferent arteriole: brings blood into the glomerulus from the renal artery Efferent arteriole: takes blood out of the glomerulus into the surrounding capillary network and then into the renal vein Nephron: Re-absorption Proximal tubule reabsorbed back into blood NaCl active transport of Na+ Cl follows by diffusion H2 O glucose HCO3 bicarbonate buffer for
blood pH Nephron: Re-absorption Loop of Henle descending limb high permeability to H2O many aquaporins in cell membranes low permeability to salt few Na+ or Cl channels reabsorbed
H2O Nephron: Re-absorption Loop of Henle ascending limb low permeability to H2O Cl- pump Na+ follows by diffusion different membrane proteins reabsorbed salts
excretion concentrated urine passed to bladder impermeable lining Osmotic control in nephron How is all this re-absorption achieved? tight osmotic control to reduce the energy cost of excretion use diffusion instead of active transport
wherever possible Summary Not filtered out Cells, proteins remain in blood (too big) Reabsorbed: active transport Na+ Cl-, amino acids, glucose Reabsorbed: diffusion Na+, Cl, H2O Excreted Urea, excess H2O , excess solutes (glucose, salts), toxins, drugs, unknowns Negative Feedback Loop
hormone or nerve signal lowers body condition gland or nervous system (return to set point) high sensor specific body condition sensor raises body condition low gland or nervous system
(return to set point) hormone or nerve signal Endocrine System Control Blood Osmolarity ADH pituitary increased water reabsorption increase thirst nephron
high blood osmolarity blood pressure low ADH = AntiDiuretic Hormone Maintaining Water Balance High blood osmolarity level too many solutes in blood dehydration, high salt diet stimulates thirst = drink more release ADH from pituitary gland antidiuretic hormone increases permeability of collecting duct & reabsorption of water in kidneys increase water absorption back into blood decrease urination
Alcohol suppresses ADH makes you urinate a lot! H2O H2O H2O Endocrine System Control Blood Osmolarity ADH increased water reabsorption pituitary
nephron high blood osmolarity blood pressure adrenal gland increase thirst increased water & salt reabsorption low JuxtaGlomerular Apparatus
nephron renin aldosterone angiotensin angiotensinogen Comparing Solute Concentrations Molecule Amount in Amount in Amount in blood glomerular urine plasma (mg/ filtrate (mg/ (mg/100mL) 100mL) 100mL)
proteins > 700 0 0 glucose > 90 > 90 0 30 30
> 1800 urea Damon, A., McGonegal, R., Tosto, P., & Ward, W. (2007). Higher Level Biology. England: Pearson Education, Inc. Diabetes & Glucose in Urine People with uncontrolled diabetes can have a large amount of glucose in their blood Glucose enters the glomerular filtrate and is reabsorbed by active transport There is a maximum rate at which reabsorption can occur If there is too much glucose in the blood, reabsorption of all glucose from the glomerular filtrate cannot be achieved Quick Check: Make Sure You Can 1. Define excretion & osmoregulation
2. Draw and label a diagram of the kidney 3. Explain the role of animal excretory systems in osmoregulation. 4. Diagram all important parts of a nephron and explain their functions. 5. Explain the processes of ultrafilatration, reabsorption, and secretion 6. Explain the role of ADH in the maintenance of the water balance of the blood.
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