EXCRETION

DEFINITION Excretion is the release of metabolic waste substances from the body. Metabolic waste are ingested substances that have been altered by the body before its accumulation and subsequent release e.g. proteins to amino acids.

EXCRETORY PRODUCTS OF PLANTS Oxygen: from photosynthesis (day) Carbon dioxide: from respiration (night) Water: from respiration (night) Nitrogenous compounds: tannins, alkaloids Calcium oxalate: solid waste products

EXCRETORY MECHANISMS IN PLANTS Stomata and lenticels for the diffusion of waste gases out of the plant Nitrogenous compounds and calcium oxalate are stored in dead permanent tissue e.g. leaves bark, flowers, fruits, seeds and will fall off the tree to be excreted.

EXCRETORY PRODUCTS IN HUMANS CO2, water, heat: from resp. N2 compounds from deamination of amino acids Bile pigments from haemoglobin break-down in the liver Ions from nutrient metabolism Heat from metabolism

ORGANS OF EXCRETION The human excretory organs are: Lungs – carbon dioxide Liver – bile, urea Skin – sweat, heat Kidney – urine, salts, excess water, urea

LUNGS After respiration, the lungs excrete the carbon dioxide and water that are the by-products. This therefore utilizes breathing and gaseous exchange. Why are nitrogen and inert gases not said to be excreted?

LIVER Deamination of excess amino acids to form carbohydrates (stored) and urea (excreted). Detoxification of poisons such as drugs, alcohol. Breakdown of red blood cells; haemoglobin is broken down to form bile pigments bilirubin and biliverdin.

LIVER The liver excretes excess proteins from the body by removing the amino (NH) groups and then storing the carbohydrate portion. The amino region is converted to urea and is released in the sweat and urine. This is called deamination. The carbohydrate is stored as glycogen for later use.

Homework List the ten functions of the liver into your notebooks. Pages 78-79 green text. Read through the details of each point for your own knowledge base.

DEAMINATION

SKIN The skin excretes salts, urea and water from the pores as sweat. Sweat glands are located in the dermis and then emerge at the surface of the epidermis as pores.

URINARY SYSTEM

THE KIDNEYS AND URINARY SYSTEM

The urinary system is composed of the kidneys which make urine the ureters which are tubes (one from each kidney) that carries urine to the bladder which temporarily stores urine until ready to leave the body through the urethra in the penis or vagina.

the kidneys which make urine the ureters which are tubes (one from each kidney) that carries urine to the bladder which temporarily stores urine until ready to leave the body through the urethra in the penis or vagina.

The renal artery carries oxygen and nutrient rich blood to the kidneys The renal vein carry deoxygenated, filtered blood to the heart.

Urinary Show Follow this link to the kidney show. LINK HOW THE KIDNEY WORKS http://www.youtube.com/watch?v=r7m5IyzQzAM&feature=fvw

The kidney itself is composed of the outer cortex the inner medulla that pinches off into structures called the pyramids that all point towards the pelvis which is the upper region of the ureter which carries urine from the kidney then to the bladder.

the outer cortex the inner medulla that pinches off into structures called the pyramids that all point towards the pelvis which is the upper region of the ureter which carries urine from the kidney then to the bladder.

THE NEPHRON Although they seem solid, the kidneys are made up of thousands of tiny tubules called nephrons.

THE NEPHRON Other names for the nephron include: kidney tubules or uriniferous tubules. 28

THE NEPHRON

THE NEPHRON Each nephron begins in the cortex, loops down into the medulla, back into the cortex and then goes down through the medulla to the pelvis where the nephrons join up with the ureter.

URINE IS MADE FROM BLOOD Urine contains the waste our kidneys filter from our blood. The nephrons filter blood under high pressure (ultrafiltration). The waste is removed as the filtrate (urine) and useful substances are left behind or reabsorbed.

COMPARE BLOOD TO URINE COMPONENTS OF BLOOD COMPONENTS OF URINE Urea Salts Water Red Blood cells White Blood cells Proteins Glucose Hormones Amino acids All Urea Some salts Some water None None (may be diabetic if present) Small amounts possible

The nephron has five regions: The Bowman’s capsule The proximal convoluted tubule The Loop of Henlé The distal convoluted tubule The collecting duct The five regions of the nephron help cleanse the blood in the following way:

BOWMAN’S CAPSULE the Bowman’s capsule in which ultrafiltration of blood occurs under high pressure.

PROXIMAL CONVOLUTED TUBULE the proximal convoluted tubule where 80% selective reabsorption occurs

LOOP OF HENLE the Loop of Henlé where mainly water is reabsorbed from the collecting ducts in order to concentrate urine.

DISTAL CONVOLUTED TUBULE the distal convoluted tubule where the remaining substances are reabsorbed.

COLLECTING DUCT the collecting duct in which more than one nephron may empty its urine into to be carried to the ureters

NEPHRON FUNCTION REGION OF NEPHRON FUNCTION Bowman’s capsule Ultrafiltration (glomerular filtrate contains water, glucose, amino acids, vitamins, hormones, salts and UREA) Proximal convoluted tubule Selective reabsorption (80% of water, glucose, salts and amino acids; most hormones and vitamins.) Loop of Henle Selective reabsorption (6% of mainly water) Distal convoluted tubule Selective reabsorption (13% of water, glucose, amino acids and salts) Collecting duct Collection of urine (1% remaining filtrate) Capillaries around nephron Selective reabsorption

ULTRAFILTRATION Thin-walled, porous glomeruli rest inside each Bowman’s capsule. Blood passing through the narrow glomerulus from the wider afferent arteriole is under such high pressure that the blood is squeezed against the glomerular walls and tiny molecules can squeeze out through their pores forming a glomerular filtrate. Glomerular filtrate contains water, salts, glucose,amino acids and urea.

USEFUL SUBSTANCES ARE REABSORBED Some of the water, salts and amino acids and all of the glucose are needed by the body so cannot be left as filtrate to make urine. They must be reabsorbed and do so as they travel along the length of the nephron. Blood capillaries leading back to the renal vein wrap around each nephron for reabsorption of substances.

These capillaries reabsorb the useful substances from the nephron and empty them into the efferent arteriole that joins up with the vein. This takes the useful substances back to the bloodstream.

Urine: The Movie THE KIDNEYS AND THE NEPHRON

Recap

Suppose the kidney stop working

HOMEOSTASIS

Keeping the internal environment of the body constant. This is done by Kidney- osmoregulation (water) Pancreas and liver- glucose concentration Lungs- carbon dioxide concentration Skin- body temperature

OSMOREGULATION

How do we gain water Drinking Eating Osmosis (plants)

How do we lose water? Sweating Urinating Breathing out

Too much water in the blood (dilute) water enters cells by osmosis which may swell and burst. Too little water in the blood (concentrated) water leaves cells by osmosis and may shrink leaving the body dehydrated.

KIDNEYS Too little water Hypothalamus detects and signals pituitary gland to secrete more ADH ADH goes to kidneys and make the capillaries around the nephron more permeable More water is therefore reabsorbed to bring balance. Urine produced is in small amount and very concentrated (yellow).

TOO MUCH WATER? WHAT HAPPENS? Hypothalamus detects and signals pituitary gland to secrete less ADH Less ADH goes to kidneys and so the capillaries around the nephron are less permeable Less water is therefore reabsorbed to bring balance. Urine produced is in larger amount and very dilute (clear and colourless).

DIALYSIS Kidneys damaged by injury or infection. Can survive with one. Can be donated to a “matched” person. If both kidneys fail, dialysis is done for up to 10 hours every few days. Dialysis fluid is same conc. as healthy blood so anything in excess will diffuse from the blood into the fluid before re-entering the body.

HOMEOSTASIS

What is Homeostasis? Homeostasis is the maintaining of a constant environment inside the body regardless of external changes.

Feedback mechanisms keep many aspects of the internal environment constant. BLOOD passing through the HYPOTHALAMUS of the brain containing too much or too little of a particular SUBSTANCE causes the HYPOTHALAMUS to send impulses to appropriate ORGANS causing them to return the level to NORMAL. This is known as NEGATIVE FEEDBACK.

If the corrective mechanism FAILS and the level cannot be returned to normal, the increase or decrease will continue. This is known as POSITIVE FEEDBACK and is rare in living organisms since it often causes DEATH.

WATER CONCENTRATION IN BLOOD One example of homeostasis is osmoregulation where the pituitary gland secretes more or less Anti-diuretic hormone (ADH) to control the amount of water in the blood/body by causing more or less urine to be made and released.

WATER CONCENTRATION IN BLOOD

WATER CONCENTRATION IN BLOOD

BODY TEMPERATURE Another example of homeostasis brings body temperature back to normal if our surroundings get too hot or cold.

BODY TEMPERATURE

BODY TEMPERATURE

BODY TEMPERATURE

GLUCOSE LEVELS Another example of homeostasis keeps blood sugar (glucose) levels normal if we eat too much or too little.

GLUCOSE LEVELS

GLUCOSE LEVELS

CO2 LEVELS IN BLOOD Another example of homeostasis keeps the level of carbon dioxide in our blood normal.

CO2 LEVELS IN BLOOD

CO2 LEVELS IN BLOOD

Too much water in the blood causes cells to absorb it by osmosis, swell and burst. Too little water in the blood causes cells to lose water and shrivel.

Being too cold is HYPOTHERMIA and this causes the heart and breathing rate to slow until death. Being too hot is HYPERTHERMIA and this causes the body to overheat and can cause stroke.

Too much sugar in the blood is a sign of diabetes and can lead to excessive thirst, nerve damage and blindness. Too little sugar in the blood can stare the brain and lead to blackouts, coma and death.

Too little CO2 in the blood will not trigger the breathing system to take breaths. Too much CO2 in the blood can lead to a build up of carbonic acid that can become toxic.

NEGATIVE FEEDBACK The way in which these organs respond to changes in the environment by brining the body back to the norm is called a negative feedback mechanism.

SKIN When a person gets too hot they start to Sweat Vasodilation occurs The hairs lie flat

When a person gets too cold: They shiver Vasoconstriction occurs The hairs stand upright

USE THIS DIAGRAM TO PRACTICE DIFFERENT FEEDBACKS

OSMOREGULATION

TEMPERATURE REGULATION

TEMPERATURE REGULATION

GLUCOSE CONCENTRATION

CO2 CONCENTRATION