Passive Transport in the Body Includes material from chapters 30 and 32

In the Digestive System… Most nutrient absorption occurs within the small intestine Specifically, most nutrients are absorbed within the jejunum Chemical digestion wraps up in the duodenum

In the Digestive System… The small intestine is lined with villi (which have microvilli) – this increases the surface area to maximize nutrient absorption

In the Digestive System… Water-soluble substances, including vitamin C, are absorbed along with water By osmosis, these substances move from the intestines to the bloodstream Small lipids also diffuse into blood

In the Digestive System… Some substances, including the sugar fructose, need transport proteins to get across the cell membrane These substances still travel down the concentration gradient – so the process is facilitated diffusion

In the Digestive System… Some disorders of the digestive system can interfere with nutrient absorption. Hemochromatosis is a condition, typically hereditary, that leads to increased iron absorption

In the Digestive System… Whipple’s disease is a rare condition caused by a bacterial infection that prevents the small intestine from properly absorbing nutrients – it causes irregular fold patterns in the small intestine and thickened walls

In the Circulatory System… Once nutrients have been absorbed by the intestines, the next step is to get these nutrients to the cells Cells need nutrients for cellular respiration, growth, repair, and other activities

In the Circulatory System… Nutrients are dissolved in the plasma (liquid portion) of the blood Plasma is mostly water, but also contains blood proteins In addition to transporting nutrients, plasma also carries hormones and electrolytes The other components of blood are cellular: red blood cells, white blood cells, and platelets

In the Circulatory System… Most nutrients are sent to the liver first for processing and storage of excess nutrients The hepatic artery takes blood to the liver The hepatic vein returns blood from the liver to the heart

In the Circulatory System… The heart is responsible for pumping blood throughout the body The pumping chambers of the heart are the ventricles

In the Circulatory System… Blood leaving the heart to go to the body – not the lungs! – is pumped out the left ventricle and into the aorta

In the Circulatory System… The blood vessels carry the blood – and the nutrients it holds – throughout the body

In the Circulatory System… There are three major types of blood vessels: 1. Arteries carry blood away from the heart; the largest artery is the aorta; small arteries are called arterioles 2. Veins carry blood toward the heart; the largest artery is the vena cava; small veins are called venules 3. Capillaries link arteries to veins; these blood vessels are so narrow that blood cells have to pass through them single file

In the Circulatory System… At the capillaries, nutrients diffuse from bloodstream to body cells – and wastes diffuse from the body cells into the bloodstream

In the Circulatory System… Many wastes will eventually be carried through the renal artery to the kidney, which will purify the blood Some of these wastes diffuse into the kidney; others are pulled from the bloodstream by active transport

In Gas Exchange… In addition to nutrients and wastes from food, the blood also transports oxygen and carbon dioxide Red blood cells carry oxygen on hemoglobin

In Gas Exchange… Oxygen enters the body through the respiratory system Air travels from the nose  pharynx  trachea  bronchi  bronchioles  alveoli

In Gas Exchange… Each alveolus is an air sac surrounded by a network of capillaries The pulmonary arteriole brings blood from the heart while the pulmonary venule carries blood back to the heart

In Gas Exchange… Oxygen diffuses from the alveolus into the capillary; it will then travel back to the heart to be pumped out to the body Carbon dioxide and water diffuse from the capillary into the alveolus; it will then be exhaled

In Gas Exchange… Certain conditions can impair gas exchange In pneumonia, an infection causes an inflammation of the lungs; the lungs often become filled with fluid

In Gas Exchange… In asthma, the airways of the lungs swell and narrow

In Gas Exchange… In emphysema, the alveoli (air sacs) are damaged -- their walls break down and the sacs become larger. These larger air sacs move less oxygen into the blood. This causes difficulty breathing or shortness of breath that gets worse over time.

In Gas Exchange… In anemia, a person has fewer red blood cells Remember, red blood cells are responsible for transporting oxygen to the body cells There are multiple types and causes of anemia