Transcript Lecture 7
Breathing, Circulation & Digestion The importance of pressure, diffusion and anatomy Lung Structure • Spongy – elastic • Very large surface area • Bronchi branch to form smaller bronchioles • Bronchioles end in grapelike bunches of alveoli – formed of alveolar sacs • >300 X 106 alveoli per human lung Surface Area to Volume Ratio 1 cm V = 1 cm* 1cm*1 cm = 1 cm3 SA = 1 cm*1cm/side = 1cm2/side 6 sides: total = 6 cm2. SA:V = 6:1 ½ cm V = ½*½*½*8= 1 cm3 SA = ½ cm*½ cm/side = ¼ cm2/side 6*8 sides: total = 12 cm2. SA:V = 12:1 Common misconception • The force of air coming into the lungs causes lungs to expand or… • Without the incoming air, the lungs won’t expand, and if the lungs don’t expand, neither can the chest. What physical property affects a gas? • Gases within a given volume exert pressure against surfaces. • What is pressure? – Force/Area = N/m2 Snow example • Snow is a weak supporting structure but spreading weight over a larger surface area can allow it to support you…..snow shoes Balloon P=F/A Relationship of Volume to Pressure Volume increases what happens to the pressure exerted by a gas? Inhalation higher low Increased volume lower pressure in the lungs - Atmospheric pressure now greater than lungs Diffusion CO2 Low O2 Low CO2 High Tissue O2 Low CO2 High Capillary O2 High Capillary Lung O2 High CO2 Low Functions of the circulatory system? THE CIRCULATORY SYSTEM Besides transporting oxygen and nutrients that sustain body processes, the circulatory system transports waste materials produced by cells. Function of a Digestive System • Dissasembly process • Large chunks to smaller molecules • Ultimately, these small molecules are taken up by circulatory system and distributed to cells The Four Stages of Food Processing • Ingestion – Is another word for eating • Digestion – Is the breakdown of food to small molecules • Absorption – Is the uptake of the small nutrient molecules by the body’s cells • Elimination – Is the disposal of undigested materials from the food we eat • Mechanical digestion – 1st step in the process of digestion – Involves physical processes like chewing – How is this done? • Teeth • Also adds water for chemical Increases the surface toreactions volume ratio of food particles but it does not break the chemical bonds within a food molecule Role of Saliva • Salivary glands made up of three glands • Amylase is responsible for initiation of starch breakdown • What’s starch? Esophagus- delivers food to stomach Nerve endings in throat/pharnx cause esophagus walls to contract which move the bolus to the Stomach. Epiglotis stops food from entering trachea, acts like a one way flap. Stomach- specialized structure for further chemical digestion Gastric juices and enzymes mix with food. These target and breakdown proteins and lipids. This mixture now leaves stomach thru pyloric sphincter and enter small intestine. Small intestine – Primary site of absorption of digested molecules More enzymes are produced in small intestine as well as…….. Hormone secretion that regulates release of food from stomach and……. The release of secretions from the pancreas and liver. Duodenum-upper portion still receives some digestive enzymes – Is the first part of the small intestine – Receives digestive agents from several organs Liver produces bile that is stored in Liver gallbladder. It is then pumped into doudenum to reduce the size of fat Gallbladder globules in a process called emulsification. Pancreasneutralizes acids from stomach by production of bicarbonate ions. Bile Stomach pH? Bile Acid chyme Doudenum pH? Pancreatic juice Duodenum of small intestine Pancreas • The jejunum and ileum – Are parts of the small intestine – Are specialized for absorption Nutrient absorption Nutrient absorption Blood vessels Microvilli Epithelial cells Interior of intestine Muscle layers Villi Blood capillaries Lymphatic vessel Epithelial cells Nutrient absorption Intestinal wall Villi Colon: Large intestine- absorption of water. Water reabsorption. Bacteria further breakdown undigested food. Bacteria add vitamins. Colon: rectum – specialized region for temporary storage Anus – exit from digestive systemseparate exit from the urogenital system The End