1. Diffusion and Osmosis in the Human Body
Circulation, excretion, respiration, and hormone production.

2. Homeostasis
Defined as one of the fundamental characteristics of all living systems
It is the tendency of an organism to maintain a stable, constant internal environment
Maintained by various organ systems in the body
An organ system is a group of organs that works together to perform a common function

3. Circulatory System
Made up of heart and various blood vessels filled with different types of blood cells and platelets
Flow of blood goes from right side of heart to left side of hear in the following path…
right atrium receives deoxygenated blood from the superior and inferior vena cava  right ventricle pulmonary artery lungs (capillaries in the lungs allow for diffusion of CO2 out of blood stream and O2 into bloodstream)  pulmonary vein left atrium  left ventricle  oxygenated blood pumped to body from aorta to other arteries

4. Circulatory System
Arteries are blood vessels that flow away from the heart and typically carry oxygenated blood… the only deoxygenated artery is the pulmonary artery
Veins are blood vessels that flow towards the heart and typically carry deoxygenated blood and CO2 waste… the only oxygenated vein is the pulmonary vein
Blood vessels get smaller as they get to areas in the body where gas exchanges must be made (lungs, body tissues, etc.) arteries branch into arterioles and veins branch into venules. Arterioles connect to venules through capillaries, the thinnest of all blood vessels. Through the walls of the capillaries, gasses are exchanged through the process of diffusion. Capillary beds have a total surface area in each human of about 6300 square meters!

5. Flow of blood in heart and body

6. Respiration and Diffusion
As you saw with your dissections, respiration depends heavily on both the circulatory system and the process of diffusion.
The passage of air into your lungs comes in through the nasal cavity  trachea  branching system of bronchial tubes in each lung  alveoli
The alveoli are lined with capillaries so that O2 you breathe in can enter the bloodstream and CO2 waste can leave the blood stream.
Like most animals, your lungs are lined with moist mucus providing a wet environment for gas exchange

7. Diffusion and Osmosis… a review
Why does the CO2 leave the blood stream and O2 enter?... Diffusion
Diffusion is a form of passive transport (no energy required) in which substances flow from an area of high concentration to an area of low concentration. Substances such as O2 and CO2, are small enough to pass through the walls of the capillaries.
A specific type of diffusion is osmosis, or the movement of water from high to low concentration due to a change in conditions (think of the eggs-periment)

8. Diffusion and Osmosis
Three types of environments can exist outside cells to effect the internal environment
Isotonic – concentration of solute is the same both in and out of cell, water movement is equal
Hypertonic – concentration of solute is greater outside the cell, water moves to the outside of cell to balance out (possibly resulting in cell shriveling)
Hypotonic - concentration of solute is lower outside the cell, water moves into the cell to balance out (possibly resulting in cell explosion)

9. Cells in the three environments

10. Diffusion and osmosis in the kidney
The main function of the kidneys is to filter our blood and remove waste as urine. Both kidneys do the same job. Blood is taken to the kidneys by the renal artery and when it is cleaned, it is returned to the heart by the renal vein. The urine is taken to the bladder by the ureters.

11. Diffusion and osmosis in the kidney
The functional unit of the kidney is the nephron. They are long coiled tubes that act as filtering units in the kidney. Each nephron has a capsule (bowman’s capsule) that is in direct contact with a capillary bed known as the glomerulus. The glomerulus is the site of filtration. The capillaries in the glomerulus drain into more arterioles that continue to help blood get filtered along the nephron before returning to the renal vein. Reabsorption takes place between the nephron tubule and the second capillary bed.

12. Diffusion and Osmosis in the kidney
Maintaining water balance in the kidney can be inhibited by a diuretic, a substance that causes the kidneys to allow excess water loss. A very common diuretic is caffeine.
Diuretics block the production of the hormone vasopressin, an anti-diuretic hormone (ADH). When the blood has a high concentration of sodium ions, the hypothalamus and pituitary gland (both in the brain) triggers the release of ADH which would tell the kidneys to reabsorb more water to help rehydrate the body. This is an example of maintaining homeostasis with the endocrine system. The endocrine system is made up of glands and cells that release chemical messengers called hormones, directly into the blood stream.

13. Hormones and Homeostasis
The endocrine system helps maintain homeostasis with positive and negative feedback.(p235)
Negative feedback involves constantly adjusting to correct and abnormal situation.
Example – production of ADH returns water balance to normal, ADH production stops
Positive feedback involves processes that must be completed quickly and the production of some hormone triggers the production of more
Example – production of chemical clotting agents at the site of a cut will trigger the production of more clotting agents to rapidly clot and minimize blood loss