Urinary System

Learning Objectives Recall the origin of CO 2 and O 2 as waste products of metabolism. Recall that the lungs, kidneys and skin are organs of excretion. Understand how the kidney carries out its roles of excretion. Describe the structure of the urinary system. Describe the structure of a nephron.

Excretion Some products of chemical reactions that occur within cells are poisonous and so must be removed. Excretion is the removal from the body of: The ______ products of its chemical reactions. The excess ______ and _____ taken in with the diet. Spent __________. D____. Any other foreign substances taken into the alimentary canal and absorbed by the blood. waste watersalts hormones rugs

Excretory Organs – Kidneys Excess amino acids are broken down in the liver, to form glycogen and ____. The ____ is removed from tissues by the _____, and expelled by the kidneys. Urea and uric acid from the breakdown of protein contain nitrogen – nitrogenous waste products. When hormones have done their job, they are modified in the liver and excreted. _____ is the watery solution excreted by the kidneys which contains the nitrogenous waste products, excess salts and ______, drugs, toxins and spent hormones. blood urea Urine water

Structure of the Kidneys Two kidneys. Fairly solid, oval-shaped structures. Red-brown in colour. Enclosed in a transparent membrane. Attached to the back of the abdominal cavity. Renal artery branches off from the aorta and supplies the kidneys with oxygenated blood. The renal vein takes deoxygenated blood back to the vena cava.

Ureter – a tube that connects each kidney to the bladder. Renal tubules – many capillaries and tiny tubes in the kidney tissue, held together with connective tissue. Cortex – dark outer region of kidney. Medulla – lighter, inner zone. Pelvis – space where the ureter joins the kidney. Glomerulus – a divided and coiled capillary leading from each arteriole. The renal artery divides up into many arterioles and capillaries in the cortex.

Renal capsule (Bowman’s capsule) – a cup-shaped organ almost entirely surrounding the glomerulus. It is a smooth semi-transparent membrane. The renal capsule leads to the renal tubule. Collecting duct – the coiled and looped renal tubule leads to the collecting duct. The collecting duct passes through the medulla and opens into the pelvis. Nephron – a single glomerulus with its renal capsule, renal tubule and capillaries. There are thousands of glomeruli in the cortex, and the surface area of their capillaries is very large.

A NEPHRON Renal capsule (Bowman’s) Glomerulus (capillaries) Renal artery (blood with waste) Renal vein (blood without waste) Loop of Henle Renal tubule Collecting duct