KIDNEYS AND OSMOREGULATION

Corresponds with chapter 36 665-675

Excretion is the removal from the body of waste products of the metabolic pathways

Excretory organs tend to be tubular in both invertebrates and vertebrates

Excretion

The breakdown of various molecules forms nitrogenous wastes.

amino acids energy OR amino acids fats or carbs

Removes the amino group (NH2) and excretes it in the form of ammonia, urea, or uric acid

the removal of the amino group requires a set amount of energy

however when converting it the energy required changes

Ammonia little energy needed H toxic requires a lot of fluids to keep it

under control N –H nitrogenous excretory product(w/ water)

fish and aquatic animals H

Urea O H2N-C-NH2

Needs energyLess toxic than ammonia Excreted in moderately concentrated solution(allows body water to be conserved)Advantage for terrestrial animals with limited access to

waterMain form of waste for sharks, adult amphibians, and

mammals

Uric acid

Long complex series of enzymatic reactions that requires a lot of ATP

Poorly soluble in water, it forms crystalsWater conservation is needed because it can

be concentrated more readily than urea, excreted in a dehydrated form

Excreted by insects reptiles and birds

Possible to predict metabolic waste based on anatomy and environment

EXTRA CREDIT:

Most animals have tubular organs that regulate the water and salt balance of the body

excrete metabolic wastes into the environment

May utilize other organs Look at three examples, the planarian, the

earthworm, and the arthropods

Excretory organs among invertebrates

Planarians two strands of branching excretory

tubules, open to the outside through the

excretory poresflame cells along the tubules.each has a

cluster of beating ciliacilia allows the fluid to move through the

body and outrids the body of excess water and

excretes waste

Earthworms body has segments and each segment has

its own excretory structure nephridianephridium has an ciliated opening and

excretory poreas fluid moves through the tubule the

composition is modifiedurine has salts, metabolic wastes, and

waterurine produced is equal to about 60% of its

body weight. Excretion of ammonia is consistent

Extra credit give an example of an animal that

doesn’t excrete what it was classified to excrete.

why not?

Insectslong set of thin tubules called Malpighian tubules

attached to the guturic acid is actively transported from surrounding

hemolymph into these tubuleswater follows salt gradient established by active

transport of K+water and other materials are reabsorbed at the

rectum uric acid excreted at the anusinsects-> water =little rebsorbtioninsects -> dry=lot of reabsorbtion-> semisolid

mass of uric acid

Arthropods (others)excretory organs given different name,but the function is similarcrustaceans remove wastes through diffusion across gillspossess excretory organ green gland, in ventral portion of head regionfluid collects in the tubules but is modified by time as it leaves

Shrimp and pill bugs have Maxillary glands in maxillary segments

Spiders, scorpions and other arachnids have coxal glands, located near one or more appendages

Spherical sacs, wastes are collected from the surrounding blood and discharged at the pores at one to several pairs of appendages

Osmoregulation- to maintain particular ion concentrations in blood

Essential to maintain homeostasis b/cIons like Ca2+, Na+, K+ and PO4- affect

systems of the body Necessary b/c few vertebrates have blood

that is isotonic to the sea water

Osmoregulation in Aquatic Vertebrates

Cartilaginous fishconcentration of various ions in blood is less than seawaterblood plasma nearly isotonic with water b/c they pump it full of ureagives their blood same tonicity of water

Do regulate concentration of solutes and have rectal glands that rids the body of excess salt

Marine bony fishBlood plasma is hypertonic to the marine environment (high in salts)

avoid getting dehydrated lose water by osmosis, counteract by drinking sea water constant drinking causes the fish to acquire lots of salt, actively transport out into the sea through the gills

kidneys conserve the waterproduces small amount of isotonic urine

Freshwater Bony Fishosmotic problems opposite to the marine gain water across gills and body surfacnever drink wateractively transport salt into blood across membrane of gills eliminate excess water by producing large quantities of dilute urine, discharge urine =1/3 of their body weight

What glands does a pill bug have? What glands does a spider have?

Extra credit

Biological systems are affected by disruptions to dynamic homeostasis

dehydration Kangaroo rat

form concentrated urine(20x more concentrated than its blood plasma)survives using metabolic water derived using cellular respirationnever drinks wateradaptions allows for it to remain in water-salt balance

Osmoregulation among Terrestrial Vertebrates

Seagulls, Reptiles, and Mammals kidneys are good at conserving water

are able to drink sea water, unlike us seabirds and reptiles have salt glands that pump the salt out

Birdsglands located near eye produces salty solution that is

excreted through nostrils and drips off In Sea Turtles salt gland is modified tear gland sea

snakes located beneath the tongue Commandeered a gland meant for another purpose to pump

salt from the blood plasma and leave behind the water.

Name two ions that affect the body systems.

Extra credit

Pg 670-673Urinary system

The Urinary System (pg 670-673) The urinary system includes the Kidneys – the major organ that regulates excretion; regulator of

blood compostion Urine – the modified filtrate made by the kidneys which is

conducted from the body by the other organs in the urinary system

Ureter – each kidney is connected to a ureter; a duct that takes urine from the kidney to the urinary bladder

Urinary bladder – where the kidney is stored until it is voided from the body

Urethra – through which the urine is voided from the body; in males the urethra passes through the penis while in females the opening of the urethra is ventral to that of the vagina

There is no connection between the reproductive and urinary system for females, but in males the urethra carries the sperm during ejaculation

Kidneys Bean shaped, reddish brown organs About the size of a fist Each adult kidney weighs between 115 and 170 grams Approximately 11 cm in length, 6 cm in width, and 3 cm thick Located on either side of the vertebral column just below the diaphragm, in the lower back, where they are partially

protected by the lower rib cage; right is lower 3 major parts of the kidney (actually 4) The 3 parts are the renal cortex, the renal medulla and the renal pelvis there is also the hilum – located medially and serves as the point of entrance and exit for the renal artery, renal vein and

ureter Renal cortex – outer region of the kidney with a somewhat granular appearance Renal medulla – consists of 6-10 (8-18) cone shaped renal pyramids that lie on the inner side of the renal cortex, the apex

of each pyramid terminates into what is called the papilla, which directs the urinary stream into what is called the minor calyx (numerous minor calyces expand into two or three open ended pouches called the major calyces, which feed into the pelvis)

Renal pelvis – the inner most part of the kidney, like a hollow chamber, also known as the expanded upper portion of the ureter (divides into 2 or 3 major calyces which divide into 8 minor calyces) ; urine collects in the renal pelvis and then is carried to the bladder by a ureter

Renal Vein – oxygen poor blood; drains the kidney and returns the blood to the superior vena cava

Renal artery – oxygen rich blood; brings blood to the kidney from the aorta

Ureter – the muscular tubes which propel urine from the kidneys to the urinary bladder

Extra credit: what is an example of an organism that uses

another gland meant for another purpose to excrete salt

Kidney diagram

Nephrons Each kidney is composed of over 1 million tiny tubules called nephrons;

approximately 1.2 million These are the functional units of the kidney Hollow tubes composed of a single cell layer The nephrons of a kidney produce urine Some are located in the renal cortex, but others dip down into the renal medulla The blind end of a nephron is pushed in on itself to form a cuplike structure known

as the glomerular capsule (bowman’s capsule) – the outer layer of the bowman’s capsule is composed of squamous epithelial cells; the inner layer is composed of specialized cells that allow the easy passage of molecules; there is a visceral layer composed of podocytes which help the kidneys filter out substances and then the parietal layer which is composed of the squamous epithelial; blood enters the nephrons at the bowman’s capsule

Then the renal artery leads to the kidney and branches into arterioles, then tiny capillaries

The glomerulus is the ball of capillaries which stays in the bowman’s capsule Blood is filtered as it passes through the glomerulus and the plasma is forced out

of the capillaries into the bowman’s capsule This plasma is now called a filtrate

continued the filtrate travels along the entire nephron, from the bowman’s capsule the filtrate

passes through the proximal convoluted tubule – lined by cells with many mitochondria and tightly packed microvilli; the longest and most convoluted segement of the nephron; its cell provides a much greater surface area for reabsorption and secretion; initially the proximal tube forms several coils followed by a straight segment which descends toward the medulla

Then simple squamous epithelium appears in the loop of Henle (loop of nephron) which has a descending and ascending limb, near the end of the thick ascending limb, the nephron passes between its afferent and efferent arterioles

This short segment of the ascending limb is called macula densa This is followed by the distal convoluted tube (lined by cuboidal cells that reabsorb

sodium and chloride from the tubular filtrate) Then several distal convoluted tubules enter one collecting duct (the distal convoluted

tubules begin a short distance beyond the macula densa and extends to the point in the cortex where two or more nephrons join to form the cortical collecting duct

The collecting duct transports urine down through the renal medulla and delivers it to the renal pelvis

The filtrate is modified to form urine as it travels along the tube, the urine moves from the collecting ducts into the ureters, then into the bladder, and finally out through the urethra

Each nephron has its own blood supply The renal artery branches into numerous small arteries, which

branch into arterioles, one for each nephron Each arteriole, named an afferent arteriole divides to form a

capillary bed, the glomerulus, which is surrounded by glomerular capsule

The glomerulus drains into an efferent arteriole which branches into a second capillary bed around the tubular parts of the nephron, these are called peritubular capillaries, which lead to venules that join to form veins leading to the renal vein, a vessel that enters the inferior vena cava

Urine formation An average human produces between 1 and 2 liters of urine There are three steps in the process of how urine is made:

filtration, reabsorption, and secretion Glomerular filtration – the movement of small molecules across

the glomerular wall into the glomerular capsule as a result of blood pressure

When blood enters the glomerulus,blood pressure is sufficient to cause small molecules such as water, nutrients, salts, and wastes to move from the glomerulus to the inside of the glomerular capusle (note that the glomerular walls are very permeable)

The molecules that leave the blood and enter the glomerular capsule are called the glomerular filtrate

Plasma proteins and blood cells are too big to enter the filtrate, so they remain in the blood as it flows into the efferent arteriole

Glomerular filtrate is protein free, but similar to blood plasma

Urine process continued Tubular reabsorption takes place when substances move across

the walls of the tubules into the associated peritubular capillary network

Osmosis of the water from the filtrate cannot occur yet because the osmolarity of the blood is essentially the same as that of the filtrate in the glomerular capsule

Sodium ions are actively pumped into the peritubular capillary and then chloride ions follow so now the osmolarity of the blood is such that water moves passively form the tubule into the blood, 60-70% of salt and water are reabsorbed at the proximal covoluted tubule

Urea is passively reabsorbed from the filtrate Tubular secretion is the second way substances are removed form

the blood and added to tubular fluid; this process is like the body removing harmful compounds not filtered in the glomerulus