Welcome to Topic 6: Basic Human Physiology!

Plan for this week! Complete 6.1 – digestion – Monday – Thursday Wednesday – help lab on DCP and CE (on demand) Friday – LAB – dissetion and food pathology/ identification tests Friday – FINAL DESIGN SUBMISSION IS DUE MONDAY - DCP and CE due

Topic 6.1: The Digestive System (3 h) Explain why digestion of large food molecules is essential Explain the need for enzymes in digestion State the source, substrate, products and optimum pH conditions for one amylase, one protease and one lipase Draw and label a diagram of the digestive system Outline the function of the stomach, small intestine and large intestine Distinguish between absorption and assimilation Explain how the structure of the villus is related to its role in absorption and transport of the products of digestion.

So….draw a digestive system! Draw and label a diagram of the human digestive system. You have 2 minutes….

Figure 24.1 The Components of the Digestive System

Simple digestion: Intracellular food processing Paramecium Food is ingested through endocytosis and forms food vacuole Food vacuole fuses with lysosome,which contains digestive juices Nutrients absorbed through membrane Vacuole refuses with membrane and waste is eliminated through exocytosis

Simple digestive systems: Extracellular food processing Food breakdown and absorption occur in compartments that are continuous with outside of organism Gastrovascular cavity : food enters + waste exits through a single opening Cnidarians (ex. Hydra) have this

ingestion mechanical digestion (processing) (e.g.chewing) chemical digestion (enzymatic hydrolysis) Secretion absorption excretion/ elimination of waste products Functions of the digestive system

The Structure of the Digestive Tract Figure 24.3

Smooth muscle shows rhythmic cycles of activity Peristalsis : waves that move a bolus (ball of food) Segmentation Churn (mixing) and fragment a bolus Let’s watch! Peristalsis in action... How does food move along the digestive tract?

Peristalsis Figure 24.4

Digestion is achieved through both chemical and mechanical breakdown Explain why digestion of large food molecules is essential Explain the need for enzymes in digestion State the source, substrate, products and optimum pH conditions for one amylase, one protease and one lipase.

Why do we need enzymes for digestion? Stephen Taylor intro to digestion/enzymes zoom into amylase...

Why do we need enzymes for digestion?

Step by step through the digestive tract explore the digestive tract UPenn animation animation of organs of digestion animation of organs of digestion

Its functions include: analysis of material before swallowing (touch, temperature, and taste receptors in tongue) mechanical processing by the teeth and tongue lubrication limited digestion (salivary amylase) Production of a food bolus for transportation to the stomach (via oesophagus) by peristalsis The pharynx provides a common pathway for air, food and liquids Oral (buccal) cavity/pharynx

The pharynx

yum!....digestion from the inside Storage of undigested food Hydrochloric acid lowers pH to 2, killing bacteria and denaturing proteins Mechanical breakdown of food through muscular action Chemical breakdown of food with acids and enzymes (pepsin begins protein digestion) Produces chyme Outline the function of the stomach

Structure of the stomach Rugae: rough ridges which allow grinding of food (mechanical digestion)

very little absorption of nutrients Control of enzyme (pepsin), acid (HCl) and hormone (gastrin) secretion is controlled by: 1.Cephalic 2.Gastric 3.Intestinal factors Control of gastric function Digestion and absorption in the stomach

The Stomach Figure 24.12b

The Stomach Lining Figure 24.13c, d

Important digestive and absorptive functions pancreas, liver & gall bladder secrete enzymes and juices into small intestine Small intestine divided into three sections: Duodenum Jejunum Ileum Outline the function of the small intestine.

Figure 24.16a Regions of the Small Intestine

Adaptations to increase surface area for absorption… Plicae (folds) Villi (fingerlike projections) Microvilli Zooming in on the small intestine Small intestine

Figure 24.17b, c The Intestinal Wall

Figure 24.17d, e The Intestinal Wall

Microvillae Microvilli (MV) are minute finger like projections of the luminal (L) plasma membrane and serve the purpose of significantly increasing surface area (as much as 30-fold) in regions specialized for absorption, such as here in the small intestine.

Duodenal glands produce mucus Ileum lymph glands (Peyer’s patches) Small Intestine

Reabsorbs water and compact material into feces Absorb vitamins produced by bacteria Store faecal matter prior to defecation Functions of the large intestine

The Large Intestine

Figure 24.18a-c The Pancreas The pancreas and gland cells of the small intestine secrete digestive enzymes that chemically break down complex food molecules into simpler ones. These enzymes include trypsin (for protein digestion), amylase (for carbohydrate digestion), and lipase (for lipid digestion).

Pancreatic duct penetrates duodenal wall Endocrine functions (hormones) Insulin and glucagons Exocrine functions (digestive enzymes) Pancreatic juice containing many enzymes are secreted into small intestine The pancreas

Performs regulation of metabolism and blood and produces bile The liver has many different functions The liver

The Gallbladder Bile liquid is created in the liver and stored in the gallbladder. Bile emulsifies (breaks into small particles) lipids (fats), which aids in the mechanical digestion of fats.

Hollow, pear-shaped organ Stores bile Helps in digestion of fats The gallbladder Animation: Accessory Organ PLAY