Chapter 17 Lecture Outline See separate PowerPoint slides for all figures and tables pre-inserted into PowerPoint without notes.

Chapter 17 Urinary System 3

17.1 Introduction 4

The urinary system consists of two kidneys that filter the blood, two ureters, a urinary bladder, and a urethra to convey nitrogenous waste substances to the outside. Helps maintain normal concentration of electrolytes and water. Regulates pH and fluid volume. Helps control red blood cell production and blood pressure. 5

Fig 17.1 6

17.2 Kidneys 7

Location of the Kidneys The kidney is a reddish brown, bean-shaped organ 12 centimeters long; it is enclosed in a tough, fibrous capsule. Location of the Kidneys The kidneys are positioned retroperitoneally on either side of the vertebral column between the twelfth thoracic and third lumbar vertebrae, with the left kidney slightly higher than the right. Connective tissue and adipose tissue hold the kidneys in place. 8

Location of the Kidneys The kidney is a reddish brown, bean-shaped organ 12 centimeters long; it is enclosed in a tough, fibrous capsule. Location of the Kidneys The kidneys are positioned retroperitoneally on either side of the vertebral column between the twelfth thoracic and third lumbar vertebrae, with the left kidney slightly higher than the right. Connective tissue and adipose tissue hold the kidneys in place. 9

Fig 17.1 10

Kidney Structure A medial depression in the kidney (hilum) leads to a hollow renal sinus into which blood vessels, nerves, lymphatic vessels, and the ureter enter. Inside the renal sinus lies a renal pelvis that is subdivided into major and minor calyces; small renal papillae project into each minor calyx. 11

Kidney structure, cont. Two distinct regions are found within the kidney: a renal medulla and a renal cortex. The renal medulla houses renal pyramids leading to the papillae. The renal cortex surrounds the medulla and dips down in-between the renal pyramids (renal columns). The functional unit of the kidney is the nephron. 12

Fig 17.2 13

Kidney Functions The kidneys function to regulate the volume, composition, and pH of body fluids and remove metabolic wastes from the blood in the process. The kidneys also help control the rate of red blood cell formation by secreting erythropoietin, and regulate blood pressure and volume by secreting renin. Plays a role in activation of vitamin D. 14

Renal Blood Vessels The abdominal aorta gives rise to renal arteries that enter the kidneys. As renal arteries pass into the kidneys, they branch into successively smaller arteries: interlobar arteries, arcuate arteries, cortical radiate arteries (interlobular arteries), and afferent arterioles leading to the nephrons. Venous blood is returned through a series of vessels that generally correspond to the arterial pathways. The renal vein then joins the inferior vena cava in the abdominal cavity. 15

Fig 17.3 16

Nephrons Nephron Structure A kidney contains one million nephrons, each of which consists of a renal corpuscle and a renal tubule. The renal corpuscle is the filtering portion of the nephron; it is made up of a ball of capillaries called the glomerulus and a glomerular capsule that receives the filtrate. 17

Nephron Structure, cont. The renal tubule leads away from the glomerular capsule and first becomes a highly coiled proximal convoluted tubule, then leads to the nephron loop (ascending and descending limbs), and finally to the distal convoluted tubule. Several distal convoluted tubules join to become a collecting duct which passes into the medulla, emptying into a minor calyx at the papilla. 18

Fig 17.6a 19

Fig 17.7 20

Blood Supply of a Nephron The glomerulus receives blood from a fairly large afferent arteriole and passes it to a smaller efferent arteriole. The efferent arteriole gives rise to the peritubular capillary system, which surrounds the renal tubule. The blood then enters the venous system of the kidney. 21

Fig 17.6b 22

Juxtaglomerular Apparatus At the point of contact between the afferent and efferent arterioles and the distal convoluted tubule, the epithelial cells of the distal tubule form the macula densa. Near the macula densa on the afferent arteriole are smooth muscle cells called juxtaglomerular cells. The macula densa together with the juxtaglomerular cells make up the juxtaglomerular apparatus. 23

Fig 17.8 24