Honors Biology - Unit 4: Gas & Waste Exchange Through the Urinary and Respiratory Systems (Part 2 of Learning Targets)

Related State of MI learning standards:

• HS-LS1-2 Develop and use a model to illustrate the hierarchical organization of interacting systems that provide specific functions within multicellular organisms.

• HS-LS1-3 Plan and conduct an investigation to provide evidence that feedback mechanisms maintain homeostasis. 

2nd Test material - gas and waste exchange through the urinary and respiratory systems

1. Identify the general functions of the urinary and respiratory systems of the human body.

• Describe the overall functions of the urinary system in the human body. What is being exchanged/balanced?

The urinary system regulates three substances in the human body. Water level is regulated, salt and ion levels in the blood are adjusted accordingly, and urea/other toxic wastes are excreted. The kidneys (nephrons) clean/filter the blood, through filtration, reabsorption, and secretion. Ureters bring the created waste product, urine, to the bladder, where it is stored until disposed of from the body. Water and waste products such as excess salts and carbon dioxide are exchanged, removed, and balanced. The exchange of such materials and waste products are essential to maintaining homeostasis.

• Describe the overall functions of the respiratory system in the human body. What is being exchanged/balanced?

The respiratory system in the human body involves the lungs, which have many parts with specialized functions. Oxygen and carbon dioxide are exchanged and balanced. Carbon dioxide is the waste gas, removed with expiration. Oxygen is taken in with inspiration. The nose & mouth warm and moisten the air with cilia, the pharynx allows air to pass through, the epiglottis covers the airway when eating, the larynx is the voice box, the trachea is the windpipe with cilia, and the two bronchi lead to the lungs (with cilia), the bronchioles are the smaller tubes, and the alveoli allow for gas exchange between respiratory and circulatory systems. The diaphragm’s contractions and relaxations allow for air to rush in and out of the lungs.

2. Explain how human body systems maintain relatively constant internal conditions.

• Explain the role the urinary system plays in maintaining homeostasis.

The urinary system plays an important role in maintaining homeostasis. Water and a variety of waste products, including excess salts and CO2 must be removed from cells and organisms. The exchange of these waste products and materials is essential to maintaining homeostasis or a balance. Humans excrete harmful nitrogenous waste as urea (changed in the liver). The kidneys use filtration, reabsorption, and secretion to remove waste, regulate blood pressure, regulate the salt-water balance, and conserve blood glucose by returning it to the blood. These actions all contribute to the human body maintaining homeostasis.

• A person eats a meal high in sodium. Trace these large amounts of sodium through the urinary system, explaining what happens throughout.

The large amount of sodium first enters the kidneys through the renal artery in unfiltered blood. Specifically, the nephrons filter the blood. The sodium enters Bowman's capsule through the Glomerulus, and it is forced in because of the high pressure. The filtering process removes everything except red blood cells and plasma molecules because they are far too big to pass through the capillary walls. The body does need some sodium as it is an essential nutrient, so a small portion may be reabsorbed. The filtrate with the sodium goes into the Loop of Henle from the Glomerulus next, and the necessary amount of sodium is reabsorbed from the Loop of Henle back into the blood using active transport (w/the use of ATP). Sodium ions are among the substances/nutrients that can be reabsorbed. The rest of the sodium is turned into waste products, which have remained in the Loop of Henle, passed through a tubule, then into collecting ducts. The collecting ducts then form urine by reabsorbing water (w/the excess sodium) and drain into the pelvis. The pelvis goes to the ureter, which takes the urine to the bladder, where excretion will eventually occur, eliminating the sodium waste out of the body.

• Explain the role the respiratory system plays in maintaining homeostasis.

The respiratory system plays an important role in maintaining homeostasis. Its function is gas exchange (primarily involving the lungs), which is a homeostatic process. Oxygen is needed by cells to make energy, while carbon dioxide is produced as the cells make energy and is later released as a waste product. The contractions of the diaphragm allow for breathing, as air moves into the lungs. Exhaled air goes out the same passage as the diaphragm relaxes. An increased breathing rate helps reduce the carbon dioxide level in the blood, and blood pH also increases to a normal level. The gas exchange process helps humans create a balance.

• Trace the movement of oxygen in and CO2 out of an earthworm, a fish, a bird, AND a human.

In an earthworm, there are no special gas exchange organs; gases are exchanged directly through their skin, with oxygen moving in and carbon dioxide out. There is a capillary inside. In a fish, water goes into the mouth, forced over the gills, and passes out of a body cavity. Gills maximize the concentration difference of oxygen between the blood in the capillaries and the water that passes over the gills. Water flows over gill disks front to back, while blood moves in the opposite direction of water. That way, the concentration difference is maximized with countercurrent exchange. The blood flows through the capillary, taking up oxygen. The blood encounters water with a high concentration of oxygen, and a diffusion gradient favoring the transfer of oxygen  from the water into blood is created. Thus, 80% of the oxygen in the water can diffuse into the blood. Carbon dioxide diffuses out of the gills into the water, conversely. In a bird, there are lungs. Two cycles of inhalation and exhalation are required for the air to pass all the way through the respiratory system. Air passes into the posterior air sacs with the first inhalation, the first exhalation moves the air into the lungs, the second inhalation moves air from the lungs to the anterior air sacs, and on the second exhalation, air flows out of the body. Since air passes through the lungs in a single direction, oxygen-rich and poor air do not have to mix, as seen in the human lungs. The air passing through the lung of a bird is always oxygen-rich; countercurrent flow is used. Birds exhale carbon dioxide to get rid of it. In a human, air (oxygen and carbon dioxide) passes through the nose through inhalation, where hairs in the nose moisten and warm it. The bronchi lead to the lungs, where air reaches microscopic cavities known as alveoli. Their thin walls are lined with capillaries; oxygen and carbon dioxide diffuse across the walls. A large volume of gas can be exchanged with the bloodstream in a short amount of time because the many alveoli of the lungs provide a great surface area. Contraction of the diaphragm causes chest volume to increase, while air pressure in the lungs decreases. The pressure difference causes air to rush into the lungs (oxygen). Carbon dioxide is expelled from a human when the diaphragm relaxes, causing the lungs to recoil and the waste gas to be pushed out.

• Know how other living organisms get rid of CO2 and other waste products (know examples from reading, too) Ok.