Biology 12 Ms. Kim

Lesson 3: Excretory System

Excretory System To maintain _________________, cells must regulate their __________ and ______ balance, as well as their ______________ concentration. Some of the most important factors that affect the water concentrations are the waste products of metabolism and cell functions, which are continuously eliminated from the body to maintain homeostasis. The body’s aqueous internal environment acts as a solvent for these wastes, and their elimination helps maintain osmotic pressure and concentration – the reason why excretion is so closely tied to the process of osmoregulation. The average adult consumes more protein than is required to maintain tissues and promote cell growth. Excess protein is often converted to carbohydrates, but proteins, unlike sugars, contain ______________. The amino group must be discarded by the body in the liver, through a removal process called ______________, the removal of an amino group from an organic compound. However, the byproduct of deamination is an extremely toxic water-soluble gas, ______________. A buildup of as little as 0.005 mg can kill humans. Fish are able to avoid this buildup by releasing small quantities through their gills, but land animals do not have this ability – wastes must be ______________. In the liver, two molecules of ammonia combine with a waste product of cellular respiration, ______________________, to form __________. Urea is 100,000 times less toxic than ammonia, and can be eliminated by the _____________. In fact, the kidney plays a crucial role in removing ___________, as well as balancing ____________________, and maintaining ________________________. As humans deplete their water reserves faster than their food reserve, for the body to maintain water balance, humans are recommended to consume 2 L of fluid daily. The average adult loses about _____ of water every day through urine, perspiration, and exhaled air, and greater volumes of water is lost when physical activity increases. Through a series of processes, we will see how the kidney plays an important role in maintaining water balance.

The Urinary System Animals maintain their ionic and pH balance and osmotic equilibrium through the ____________ of waste products and foreign matter from the body via the ______________ system, of which the its main organs are the ______________and ______________. The kidney can filter out ______________ and eliminate them from the body, while maintaining the ______________and _______ balance of the internal environment. The bladder then ______________ the urine until it is excreted out of the body. The urinary system of all vertebrates, including humans, uses specialized tubules, called ______________. These tubules are located in the major organs of the urinary system – the kidneys. The kidneys, ______________, bladder, and _____________ together make up the human urinary system.

Learning Goals:

1. How does the urinary system help maintain homeostasis? 2. Describe the anatomy of the kidneys 3. List the components of a nephron and their basic roles 4. Know the 3 parts of urine formation

Biology 12 Ms. Kim The Kidney As mentioned above, the kidneys play a crucial role in removing wastes, balancing blood pH, and maintaining the body’s water balance. Mammals have two kidneys, and blood is supplied to the kidney through the _________________ (“renal” = kidney). The kidney _____________ the wastes from the blood, and the clean blood exits the kidney through the _______________. The outer layer is the _______________, the inner layer is the ____________, and a hollow cavity called the _______________ connects the kidney to the ___________, through which urine passes to the _____________. Urine exits the body through the ____________to the bladder to be stored until excreted. In addition to urine formation, the kidney has many important functions which may include regulating:

• Blood ___________ and _____________ by regulating the amount of water to be excreted and reabsorbed • _________________ in the blood by controlling the secretion and reabsorption of _____ and _____ ions • ________ of the blood by controlling the secretion and reabsorption of _______ ions • __________________________ by secreting ______________________ (↑ production of RBCs)

The Nephron: Overview The basic structural and functional unit of the kidney is the ______________, which has three major parts: The Bowman’s capsule, the glomerulus, and the tubule. Differentiated regions help nephrons to ____________ nutrients and water, balance ________, and concentrate _____________ for excretion via the arrangement of the loop of Henle, the differences in permeability of successive parts of the nephron, and the concentration gradient of molecules and ions in the ___________________ of the kidney, which gradually increases from the cortex to the medulla. Urine formation is a result of three interrelated processes:

(1) ________________ – occurs as body fluid move _________ the blood, ______ the bowman’s capsule, where the glomerulus performs the first steps in the filtration of ________to form _________

(2) ________________ – transfers essential solutes and water ________ the nephron, back ________the blood

(3) _________________ – removal of waste products _________ the blood and interstitial fluid, back ________ the nephron

Biology 12 Ms. Kim Filtration Small branches from the renal artery, the _____________________, supply the blood to the kidney, which moves into a capillary bed called the ______________, where the first steps of filtration occur. The glomerulus is enclosed by a small folded structure, the ____________________, which allows small molecules and water to pass, and filters out larger molecules. The fluid that is filtered is known as the filtrate. Reabsorption and Secretion

From the capsule, the concentrated filtrate moves into the _______________________________ that lies in the renal cortex. Here, water and nutrients are _________________ into the blood by entering the _________________________, a network of capillaries that wrap around the kidney tubule. The filtrate flows from the proximal tubule, descends into the _____________ and forms a U-shaped structure called the ______________. The Loop of Henle concentrates the filtrate by removing more __________ from it. The loop of Henle rises again into the __________, during which ________ are removed. The ascending portion of the loop of Henle forms the _______________________ , where the salt concentrations of filtrate and the _________________________ are balanced via the additional reabsorption of water and salts. The distal tubule drains the resulting urine into a branching system of ______________________ that lead to the __________________, where additional ____________ may be reabsorbed. Urine is then collected in the renal pelvis, emptied through the ____________ to the ____________ to be stored until excreted Questions

1. How does the urinary system help maintain homeostasis?

Biology 12 Ms. Kim 1. What are the different parts of the urinary system? Draw a sketch below.

1. Describe the flow of fluid through a nephron and to the external environment. Include a simple labelled sketch with your description.

2. Fill in the chart below by describing what happens at the following structures: Structure Description Afferent arteriole

Bowman’s capsule and glomerulus

Efferent arteriole

Peritubular capillaries

Proximal convoluted tubule

Descending portion of the loop of Henle

Ascending portion of the loop of Henle

Distal convoluted tubule

Collecting ducts

Additional Reading (Nelson 2003) Read: Pg. 346-348 Next Class Lesson 4: Excretory System Pt. 2 (pg.349-352)