Chapter 35 The Urinary System Lecture Outlines by Gregory Ahearn University of North Florida Copyright 2011 Pearson Education Inc Chapter 35 At a Glance 35 1 What Are the Basic Functions of Urinary 35 3 What Are the Functions of the Human Urinary 35 4 What Are the Structures of the Human Urinary Systems System System 35 5 How Is Urine Formed and Concentrated 35 6 How Do Vertebrate Kidneys Help Maintain Homeostasis Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 35 1 What Are the Basic Functions of Urinary Systems Urinary systems help maintain homeostasis the relatively constant internal environment required to preserve health and life Urinary systems regulate the composition of the blood and extracellular fluid the watery substance that bathes all cells They also help control the concentration or osmolarity of dissolved substances in cells and in their extracellular environment Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 35 1 What Are the Basic Functions of Urinary Systems Urinary systems help maintain homeostasis the relatively constant internal environment required to preserve health and life continued A second function of urinary systems is excretion or the removal of unwanted substances from the body Urinary systems produce urine which contains the waste products of cellular metabolism Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 35 1 What Are the Basic Functions of Urinary Systems Urinary system functions are performed through three basic processes Blood or extracellular fluid is filtered removing water and small dissolved substances Nutrients are selectively reabsorbed back into the filtered fluid Excess water excess nutrients and dissolved wastes are excreted from the body in urine Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 35 3 What Are the Functions of Vertebrate Urinary Systems Kidneys are the organs of the vertebrate urinary system where the blood is filtered and urine is produced Because vertebrates live in such a wide variety of habitats vertebrate kidneys face radically different challenges in maintaining constant conditions within their bodies Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 35 3 What Are the Functions of Vertebrate Urinary Systems The kidneys of humans and other mammals perform many homeostatic functions The mammalian urinary system consists of the kidneys ureters bladder and urethra These organs filter the blood collecting and then excreting the dissolved waste products in urine During filtration water and dissolved molecules are forced out of the blood The kidneys then return to the blood nearly all of the water and nutrients required by the body The urine retains wastes which are expelled from the body Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 35 3 What Are the Functions of Vertebrate Urinary Systems The mammalian urinary system helps maintain homeostasis in several ways by Regulating blood levels of ions such as sodium potassium chloride and calcium Maintaining proper pH of the blood by regulating hydrogen and bicarbonate ion concentrations Regulating the water content of the blood Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 35 3 What Are the Functions of Vertebrate Urinary Systems The mammalian urinary system helps maintain homeostasis in several ways by continued Retaining important nutrients such as glucose and amino acids in the blood Eliminating cellular waste products such as urea Secreting substances that help regulate blood pressure and blood oxygen levels Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 35 3 What Are the Functions of Vertebrate Urinary Systems Urea is a waste product of protein digestion An important function of most urinary systems is to eliminate nitrogenous nitrogen containing wastes that are formed when cells break down amino acids Nitrogenous wastes from cells enter the blood as ammonia NH3 which is toxic The livers of humans and other mammals convert ammonia into urea which is less toxic Urea is filtered from the blood by the kidneys and then excreted in the urine Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 35 4 What Are the Structures of the Human Urinary System The urinary system consists of the kidneys ureters bladder and urethra Kidneys are paired organs located on either side of the spinal column just above the waist Blood enters each kidney through the renal artery and after the blood has been filtered it exits through the renal vein Urine leaves each kidney through a narrow muscular tube called the ureter Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 35 4 What Are the Structures of the Human Urinary System The urinary system consists of the kidneys ureters bladder and urethra continued Rhythmic contractions of the ureter transports urine to the bladder a hollow muscular chamber that collects and stores blood The bladder wall is lined with smooth muscle and is capable of considerable expansion accommodating up to a pint of urine Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 35 4 What Are the Structures of the Human Urinary System The urinary system consists of the kidneys ureters bladder and urethra continued Urine is contained within the bladder by two sphincter muscles The internal sphincter located where the bladder joins the urethra opens automatically during the reflexive contractions of the smooth muscle The external sphincter located slightly below the internal sphincter is under voluntary control allowing the brain to suppress urination unless the bladder becomes overly full urethra a single narrow tube that conducts urine outside the body When open the sphincters allow urine to flow into the Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 35 4 What Are the Structures of the Human Urinary System The structure of the kidney supports its function of producing urine Each kidney contains a solid outer layer consisting of the renal cortex which overlies an inner layer called the renal medulla The renal medulla surrounds a branched funnel like chamber called the renal pelvis which collects urine and funnels it into the ureter Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 35 4 What Are the Structures of the Human Urinary System The renal cortex of each kidney is made up of more than 1 million microscopic filters called nephrons Each nephron has two major parts The glomerulus which is a dense
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