1. Mackenzie Saltmarsh, Avani Ganatra, and Alina Em
Excretory System
Mackenzie Saltmarsh, Avani Ganatra, and Alina Em

2. Structure and function of excretory mechanisms.
Kidneys are bean shaped organs located on the lower back which filters blood, removes waste, and produces urine.
Ureter transports urine from the renal pelvis to the bladder.
Bladder temporarily stores urine prior to urination
Urethra is a tube that allows the urine to leave the body.

3. Structure and function of the parts of the kidney.

4. Renal Capsule: outer membrane that surrounds the kidney; it is thin but tough and fibrous
Renal Artery: branches off of the aorta bringing oxygenated, waste-filled blood into the kidney for filtering in the nephrons; the renal artery is further subdivided into several branches inside the kidney.
Renal Cortex: the outer region of the kidney; extensions of the cortical tissue, contains about one million blood filtering nephrons
Renal Medulla: is the inner region of the kidney contains 8-12 renal pyramids. The pyramids empty into the calyx.
Medullary pyramids: formed by the collecting ducts, inner part of the kidney

5. Renal Pelvis: is the basin-like area that collects urine from the nephrons. It narrows into the upper end of the ureter
Calyx: extension of the renal pelvis; they channel urine from the pyramids to the renal pelvis
Renal Vein: removes the deoxygenated blood from the kidneys to the inferior vena cava and back to the heart.
Nephron: filtration units in the kidneys

6. Structure and function of parts of a nephron.

8. Glomerulus: Bundle of capillaries that performs the first step of filtering blood in the kidneys. Filters small solutes from the blood.
Bowman’s Capsule: a capsule shaped membranous structure surrounding the glomerulus of each nephron.
Afferent Arteriole: connects the renal artery to the glomerular capillary network, starting the filtering process. It also takes action that controls blood pressure.
Efferent Arteriole: Blood exits out of the capillaries (glomerulus)
Peritubular capillaries: tiny blood vessels, supplied by the efferent arteriole, that travel alongside nephrons allowing reabsorption and secretion between blood and the inner lumen of the nephron.

9. Proximal Convoluted Tubule: Reabsorbs ⅔ of filtered Na (65-80% of Na) and water and all of the glucose and amino acids. It also reabsorbs a fraction of the bicarbonate, potassium, phosphate and calcium. It secretes ammonia, which functions as a buffer for secreted H+; adjusts filtrate pH. It also secretes creatine which is used to access the function of the kidney.
Loop of Henle: the part of a kidney tubule that forms a long loop in the medulla of the kidney, from which water and salts are reabsorbed into the blood.

10. Ascending Limb: Water and salts are reabsorbed into the blood.
Descending Limb: Aquaporins allow water to pass from the filtrate into the interstitial fluid.
Distal Convoluted Loop: Actively reabsorbs sodium and chloride. Relatively impermeable to water, but in the presence of antidiuretic hormone its permeability to water increases making urine concentrated. It secretes ammonium ions and hydrogen ions. Forms part of the juxtaglomerular apparatus.
Collecting Duct: reabsorbs solutes and water from the filtrate.

11. What is Urea?
The human body can’t store excess amino acids so they get stored as carbs or fats.
Amino Acids have the amine group which isn’t used in the process of turning amino acid to carbs or fat.
The Amine group become NH3 which is very toxic so the liver makes it safe by turning ammonia into urea.
Urea also has a high concentration of sodium.

12. Filtration
Filtration is the process of removing the waste from the blood. Blood pressure forces the plasma into the glomerulus from the afferent arteriole. Because the glomerulus is very porous, water, glucose, ions, and waste products (urea) get dumped into the capsule. The water, ions, glucose, and urea are now called filtrate.

13. Reabsorption
Starts at the proximal convoluted tubule which have walls that are made up of cuboidal epithelial cells. These cells reabsorb the sodium by using active transport. The epithelial cells have microvilli which increase surface area.
Water is then absorbed through osmosis
Then the filtrate goes into the ascending limb where it actively pumps out salt into the medulla. This causes a sodium gradient in the Medulla which helps the body reabsorb water when passing through the loop of henle. This is passive transport.

14. Secretion
Through the peritubular capillary network, extra wastes like hydrogen ions or drugs will be removed from the blood and into the filtrate using active transport.
At the end of secretion, the filtrate is now officially urine, and will be sent to the collecting ducts.

16. Aldosterone and Antidiuretic Hormone
Aldosterone: Aldosterone regulates the balance of water and electrolytes in the body, encouraging the kidney to excrete potassium into the urine and retain sodium, thereby retaining water.
Antidiuretic Hormone (ADH): causes increased water reabsorption at the collecting duct by increasing the water permeability of the collecting ducts. Water then moves back into the blood by osmosis. More ADH is secreted when the body needs to retain more water and this will lead to a concentrated urine.

17. Definition: The maintenance of water potential in order to keep fluid and electrolyte balance in both marine and freshwater fish.
Marine Fish: The sodium concentration of the environment (seawater) is higher than in the body, so the water in the fish will diffuse out. To gain water the fish will continually be taking in sea water and the salt will be excreted through the gills. These fish have relatively smaller kidneys.
Freshwater Fish: The sodium concentration is higher in the body than it is in the water, so the fish will swell without active transport of water out. These fish will have larger kidneys due to the need to produce more urine.
Osmoregulation

18. Contractile Vacuoles Flame Cells
Protozoans: a single-celled microscopic animal of a group of phyla of the kingdom Protista. Ex amoeba
Helps the process of osmoregulation and helps prevent rupture in cells due to water influxes in protozoans.
A specialized excretory cell found in the simplest freshwater organisms.
Flame cells function like a kidney; filtering out waste. And, they tend to be part of a system that functions as the excretory system.

19. Nephridia
The parts of the Nephridia: Metanephridia, Nephrostome and Excretory pore
Metanephridia: An excretory gland found in invertebrates. The glands consisting of tubuals pumps water with excess waste to the nephrostomes.
Nephrostome: A funnel-shaped opening of a typical nephridia. The opening is covered on the inside with cilia which helps push out water waste.
Excretory Pore: Secretes materials from large membrane-bound vesicles.

20. Malpighian
Found in insects, the malpighian tubules branch off the digestive tract. These tubules catch nitrogenous waste and water. The waste is then crystallized and removed through the rectum.

21. Mechanisms for Removing NH3
In Aquatic Animals: The research for the removal of ammonia in aquatic animals is still controversial. The ammonia is removed through gills, but the protein that breaks it down is unknown.
In Mammals: Mammals convert NH3 into urea. Urea is a very soluble liquid that is neither acidic or alkaline; and it is removed through urine. Urea is made through the urea cycle. This cycle starts in the mitochondria and then finishes in the cytosol of the cells.
In Birds, Insects, and Reptiles: These organisms use uric acid to remove ammonia rather than urea. The uric acid breaks down the compounds of ammonia and then excretes it.

22. Resources
y_System_Nephron_Diagram.php
y_System_Kidneys_Actions.php
biology/chapter/nitrogenous-wastes/