The Excretory System

Learning Objectives OB20 Understand the structure and function of the urinary system: the bladder, renal artery, renal vein, ureter, urethra and kidney OB21 Name the products of excretion: CO2, water and urea OB22 Understand the function of the skin in the excretion of waste products made in the body Above are the learning objectives as outlined in the Junior Cert Syllabus

Excretion “Process by which the body removes toxic waste substances that have been produced by the body’s own cells” If the toxic substances, which have been produced as a by-product of the body are not removed they are poisonous and can harm the body’s cells

Organs of Excretion 1 Lungs Excrete CO2 and H2O o o o o The CO2 and H20 are by-products of cellular respiration and are breathed out by the lungs. To revise the respiration link please clink on the hyperlink. o H o c o H

Organs of Excretion 2 Skin Excretes H2O and salts as sweat section of skin sweat gland blood capillaries pore Sweat is removed from the skin via the sweat ducts, as well as salts and water sweat also contains a small concentration of urea. When temp of body raised sweat acts as a cooling factor on the skin

Organs of Excretion 3 Kidneys Excrete H2O, salts, and urea as urine Kidneys are part of the urinary system. Urea is produced by the breakdown of excess protein in the liver. Urine has the same components of sweat but the urea is at a higher concentration.

Location of kidneys Humans have two kidneys. They are located in the abdominal cavity, towards the back. They are protected by fatty tissue. Humans have two kidneys. They are bean-shaped organs, approximately 11.5 cm long, situated in the abdominal cavity, just below the ribcage, one on either side of the spine. They are embedded in fatty tissue for protection.

Kidney Fatty tissue surrounding a kidney. As the kidney has no bones surrounding them they require the fatty tissue to act as a shock absorber.

Urinary system bladder Renal vein Renal Artery Kidney Ureter Bladder Urethra Clink on “Urinary system” to access hyperlink to site on the urinary system. (Internet connection required). Urea is filtered from the blood in the kidneys, carried to the bladder for storage via ureter, then excreted from body via urethra.

Formation of Urea Excess Protein Liver breaks down excess protein and converts amino groups to urea Amino acids are the simplest form of protein and cannot be stored in the body and therefore need to be removed via excretion Liver

3 2 1 What three things have you learned? What two things were new to you? What one thing do you want to learn? 2 1

Define the term excretion Excretion is the process by which the body removes toxic waste substances that have been produced by the body’s own cells.

How is CO2 formed? Lungs take in O2 so that it can be used by the cells to get energy from food, i.e., in respiration. CO2 is a by-product of the energy production system (respiration). Lungs take in oxygen to be used by the cells to extract energy from food

What are the components of sweat? Salt & water (and a small amount of urea in some sweat glands)

Urea How is urea formed? Breakdown of amino acids in the liver. synthesised by Wöhler in 1828 Urea N H C O How is urea formed? Breakdown of amino acids in the liver. It is a relatively simple nitrogen compound with two amino groups (-NH2) and much less toxic that NH3. It is the body’s way of getting rid of the amino groups from amino acids that are no longer needed.

Where are the kidneys located? In the abdominal cavity

The kidney is usually covered in a layer of fat can you suggest a reason for this? For protection.

Lesson Two OB23 Recall that waste products are removed from the bloodstream by filtration in the kidneys in the form of urine, which contains urea, water and salts, and that urine is stored in the bladder before being released from the body

Urinary system bladder Renal vein Renal Artery Kidney Ureter Bladder Urethra Clink on “Urinary system” to access hyperlink to site on the urinary system. (Internet connection required). Urea is filtered from the blood in the kidneys, carried to the bladder for storage via ureter, then excreted from body via urethra.

The Renal Arteries Renal Arteries Impurities in the blood are removed in the kidneys. Aorta collects O2 from heart, deposits it around the body, goes to kidneys with impurities, blood is filtered in the kidneys.

Renal artery in kidney Blood in renal artery is filtered in the nephrons. Once the blood has been filtered of impurities it returns to the heart via the renal vein.

Renal Veins Renal veins contain little O2. Blood returns to heart via the inferior vena cava, and is pumped to the lungs for O2 via the pulmonary artery Blood returns to the heart from the kidneys via the inferior vena cave, once in the heart the de-oxygenated blood goes to the lungs via the pulmonary artery where it can deposit the CO2 and collect O2.

Circulatory System Link the circulatory system and the excretory system by recapping, link to circulatory and excretory are in above hyperlink

Ureters Ureters conduct urine from the kidneys to the bladder. From the kidneys, urine travels down two thin tubes called ureters to the bladder. The ureters are about 8 to 10 inches long. Muscles in the ureter walls constantly tighten and relax to force urine downward away from the kidneys. If urine is allowed to stand still, or back up, a kidney infection can develop. Small amounts of urine are emptied into the bladder from the ureters about every 10 to 15 seconds.

Bladder Bladder (stores urine) The bladder is a hollow muscular organ shaped like a balloon. It sits in your pelvis and is held in place by ligaments attached to other organs and the pelvic bones. The bladder stores urine until you are ready to go to the bathroom to empty it. It swells into a round shape when it is full and gets smaller when empty. If the urinary system is healthy, the bladder can hold up to 16 ounces (2 cups) of urine comfortably for 2 to 5 hours.

Urethra Expulsion of urine from the body, controlled by the sphincter muscle. Circular muscles called sphincters help keep urine from leaking. The sphincter muscles close tightly like a rubber band around the opening of the bladder into the urethra, the tube that allows urine to pass outside the body Urethra

Kidney failure Kidney failure prevents toxic substances being excreted. Dialysis removes blood, filters it and returns it to the body. A more detailed explanation can be found through the hyperlink

Through which blood vessel of the kidney does the blood return to the heart? Through the renal vein.

Urine is passed from the kidneys to the bladder through tubes called ….? Ureters

The function of the bladder is to store... Urine

Urine passes out of the body through a tube called the ……? The urethra

What is the function of the sphincter muscle? It controls the release of urine from the body. This is usually a voluntary action.