6.1 Introduction to the Urinary System
Fig.6-1 Male Urinary System
Task 1 Fill in the numbered blanks according to the video.
The renal system consists of the kidneys，the connecting arteries and veins，and the 1.________.The kidneys are paired，bean-shaped organs，lying outside the 2.________in the back of the upper abdomen，one on each side of the vertebral column.The kidneys function as the body’s main excretory organs，eliminating the body’s metabolic waste products by filtering the blood.Substances that are unneeded or are present in excess are filtered out of the blood and form into urine，moving via the ureter into the bladder before being expelled through the 3.________.The kidneys also selectively reabsorb those substances that are needed to maintain the normal composition of the blood.By adjusting blood composition，the kidneys are able to maintain blood volume and pressure，ensure the proper balance of sodium，chloride，potassium，calcium，hydrogen，phosphate and pH，and eliminate products of metabolism，such as urea，4.________and creatinine.(https://www.daowen.com)
The medial border of the kidney is indented by a deep fissure called the hilus，where the blood vessels，nerves and ureters connect to the kidney.The kidney is composed of up to 18 lobes.Each lobe is composed of nephrons.Nephrons are the functional units of the kidney，and each kidney contains more than one million nephrons.Each nephron consists of a glomerulus and a system of tubules.The glomerulus is a unique，high-pressure mass of capillaries that filters the blood.The glomerulus is encased in a thin 5.________capsule called Bowman’s capsule.The space inside the capsule and surrounding the glomerulus is called Bowman’s space.6.________fluid is filtered from the capillary blood into Bowman’s space through the glomerular filtration membrane.The glomerular filtration membrane consists of three layers of capillary wall，the 7.________，the basement membrane and epithelium.This membrane allows some 8.________from the blood to pass through，but not all.The fluid that is filtered from capillary blood into the Bowman’s space is called filtrate and forms the 9.________urine.The filtrate then diffuses across Bowman’s space and into the tubule system of the nephron.In the tubules，some substances are added to the filtrate as part of the urine formation，and some substances are reabsorbed out of the filtrate and back into the blood.The nephron tubule is divided into four segments.The filtrate passes through each of these segments before reaching the ureter：a highly coiled segment called 10.________convoluted tubule，which drains the Bowman’s capsule，and where almost complete absorption of nutritionally important substances takes place；a thin loop structure called a Loop of Henle，which reabsorbs water and irons from the urine，and plays a role in controlling the concentration of urine；a distal coiled portion called the distal convoluted tubule，which regulates potassium，sodium and PH，and where further dilution of the urine takes place；and the collecting tubule，which joins with several tubules to collect the filtrate and where final sodium regulation takes place.
