Excretion of Liquid Waste

Chapter 49By: Kayla Nida

This system is needed to allow for removal of impurities and waste from the body.

Helps maintain homeostasis in the body◦ Regulating Body temperature◦ Regulating Blood glucose◦ Oxygen◦ pH concentrations

Why do We need this?

How this system came to be:Earthworms Insects

Contain Nephridia, which are similar to the human kidney.

Obtain fluid from the body through the filtration system called Nephrostomes◦ Removes salt through

active transport◦ Forms urine

Have Malpighian tubules◦ Urine is not formed by

filtration ◦ Waste molecules and

potassium are secreted into the tubules trough active transport

◦ Most of the potassium and water is reabsorbed into the circulatory system through the hind gut

Vertebrate Kidney Kidneys first developed among bony fish

◦ Body fluids are hypotonic to surrounding sea water so water leaves their body by osmosis through the gills and urine

◦ Drink large amounts of sea water to compensate◦ Kidney is needed to get rid of the divalent ions, such as

salt Cartilaginous Fish

◦ Kidney helps to reabsorb urea from the nephron tubule and maintain a blood urea concentration a 100 times higher than mammals

◦ Urea makes the blood isotonic to the sea water, preventing water loss

Kidney in Amphibians: first terrestrial vertebrate ◦ Identical to fresh water fish◦ Makes sense because they stay in moist places◦ Transport sodium across their skin from surrounding

water Reptiles

◦ Fresh water reptiles have similar kidneys to amphibians

◦ Marine reptiles tend to lose water and obtain a lot of salt Process similar to bony fish; eliminate excess salt

through salt glands

Vertebrate Kidney Continued:

Only ones able to produce urine with a higher osmotic concentration than their body fluid

Can excrete waste in small amounts so that more water can be retained in the body

Human kidneys can produce urine that is more than 4.2 times concentrated as blood plasma

Only ones to have loop of Henle that produces the hypertonic urine

Kangaroo rat kidneys are so efficient that it never has to drink water!

Birds and Mammals

Nitrogen containing by-products that must be removed from the body though urine◦ Ammonia- toxic to cells and only safe in very

dilute concentrations◦ Urea- mammals excrete ammonia in this form

water soluble and can be excreted in large amounts through urine

◦ Uric acid- Humans, Apes, and Dalmatians lack enzyme uricase, which converts uric acid into a more soluble derivative and must

excrete the uric acid

Nitrogenous Wastes

Nitrogenous Waste

Fist sized organ located in the lower back ◦ Juxtamedullary nephrons- long loops

that go deeply Receives blood from a renal

artery from which urine is produced

Ureter: where urine drains and carries it to the urinary bladder

Renal pelvis: mouth of the ureter when flared up◦ Has cup-shaped extensions

that receive urine from renal tissue

◦ Tissue is split into an outer renal cortex and inner renal medulla

Mammalian Kidney

Each kidney contains 1 million nephrons into the medulla◦ Cortical nephrons – shorter

loops Each nephron consists

of a long tubule and small blood vessels

Nephron: Structure and Filtration

Glomerulus- a group of capillaries in the renal cortex Capillaries filter the blood

Filtrate enters the first region of the nephron tubule= Bowman’s Capsule

Proximal convoluted Tubule- sends filtrate to the loop of Henle

Fluid is then sent to the Distal Tubule, which drains into the collecting duct

All the collecting ducts merge in the medulla to empty the urine

Filtration Reabsorption

4 functions of the Kidney

Reabsorption and Secretion in Glomerulus

Reabsorption Secretion

Driven by active transport and secondary active transport

Reabsorbs glucose, amino acids, and other molecules needed by the body

Moves out of tubules and into the blood

Moves from the blood and into the tubule to be excreted

Involves the transport of molecules across the capillaries and kidney tubules into the filtrate

Elimination of nitrogenous wastes, potassium, and other ions

Urin’s high hydrogen concentration helps maintain the acid base balance of the blood from 7.35-7.45

Maintains blood volume and pressure because of the excretion of water◦ More water excreted means lower blood volume

and visa-versa Important for homeostasis

Excretion

Include volume of blood, blood pressure, and osmolality of blood plasma

Antidiuretic Hormone (ADH)◦ Produced by hypothalamus and

secreted by pituitary gland◦ Secreted when a person is

dehydrated or eats salty food, making you thirsty

◦ Causes walls of distal tubules and collecting ducts to become more permeable to water= conserving water

Hormones Control Osmoregulatory functions

Aldosterone and Atrial Natriuretic Hormone

Aldosterone- secreted by the adrenal cortex◦ Stimulated by the drop in blood sodium

concentration◦ Stimulates the distal convoluted tubules and

collecting ducts to reabsorb sodium, decreasing the excretion of sodium in the urine

◦ Promotes secretion of potassium to help regulate the potassium concentrations in the blood

Atrial Natriuretic Hormone (ANH)◦ Secreted by the right atrium of the heart in response

to an increase in blood volume◦ Promotes excretion of salt and water into the blood

to lower the blood volume

The Kidneys maintain a constant internal environment

When affected by disease, a rise in the blood concentration of waste products, disturbances of electrolyte balance, and failure of blood pressure regulation occur

This causes other systems to develop problems because the homeostasis is thrown off

Other Systems Depend on the Kidney

Kidney disease- gradual and permanent loss of kidney over time.◦ Five stages of severity ◦ Cured by replacing the kidney, watching your

diet, some antibiotics Gout- build up of uric acid in the body

because the kidneys cannot process it correctly ◦ Causes joint pain and kidney stones◦ Diet change and antibiotics are used to help

clear it Nephritis- inflammation of the nephron

◦ Can suffer permanent damage= chronic◦ Most can be cured but severe cases have ◦ lead to death

Diseases with the Excretion of Liquid Waste