PROCESSES and PHYSIOLOGY DIGESTIVE SYSTEM PROCESSES and PHYSIOLOGY Swallowing Peristalsis Absorption Key Organs Gut Feedback

Fig. 12.1

SWALLOWING

PERISTALSIS

Duodenum  Jejenum  Ileum SMALL INTESTINE Duodenum  Jejenum  Ileum

Fig. 12.6 Small Intestine

It’s all about surface area 1.Plicae 2. Villi 3. Microvilli

VILLI Microvilli

Its All About Active Transport Products of Carbohydrate and Protein Digestion are actively transported from small intestine into the villus. These simple sugars and amino acids are taken into the capillary bed in the villus and transported to the Liver. Products of Fat digestion are absorbed into the central lymphatic vessel called a LACTEAL

DUODENUM Functions The Duodenum is only about 30 40 cm (15 inches long) but it plays a couple of very important roles: 1. Receives incoming Stomach Chyme, Pancreatic Juices and Bile from Liver and Gall bladder. 2. Secretes digestive juces/enzymes from duodenal glands

Large Intestine Functions 1. Receives undigested waste and helps absorb fluid (water) from those wastes back into the bloodstream, to help keep us from dehydrating. 2. Helps compact and form feces. 3. Harbours helpful bacteria which can further break down wastes to free up minerals and some bacteria will help produce and free up some vitamins, such as Vitamin K

Accessory Organs and Feeback Control GASTRIC GLANDS PANCREAS LIVER GALL BLADDER

GASTRIC GLANDS Some gastric glands are classified as being EXOCRINE. ???? They are responsible for producing gastric juice which consists of mucous, HCl, Pepsinogen and water. In the presence of HCl the Pepsinogen converts to active Pepsin. This Pepsin is a PROTEASE enzyme, breaking proteins into smaller peptide chains

When the stomach receives a meal, it gets turned on! Stomach control When the stomach receives a meal, it gets turned on! The stomach’s exocrine glands are turned on by a Hormone called GASTRIN. Gastrin is produced and released from the stomach’s ENDOCRINE glands????

PANCREAS Function The pancreas is a glandular organ that acts both as an Exocrine Gland and also as an Endocrine Gland. We mostly focus on its exocrine role. It produces a variety of hydrolytic digestive enzymes that help chemically finish off the digestion of Carbohydrates, Fats and Proteins.

Pancreatic Exocrine Function When acidic chyme from the stomach enters the duodenum, the pancreas is stimulated to secrete pancreatic juice

Pancreatic Juice INGREDIENTS: Sodium Bicarbonate – NaHCO3? LIPASES? PANCREATIC AMYLASE? TRYPSIN – same function as PEPSIN NUCLEASES (work on Nucleic Acids)?

Pancreatic Endocrine Function When blood sugar is getting too high. The pancreas produces and secretes INSULIN into the bloodstream

Pancreatic Endocrine Function When blood glucose levels start getting too low, the Pancreas will produce and secrete the hormone GLUCAGON. Glucagon will travel through the bloodstream to tell muscle and liver cells to break down their stored Glycogen back into glucose and send it back into the blood, to raise blood sugar levels

Liver Functions

Gall Bladder Function The gall bladder is a sac-like oran that sits inferior (below) the liver. It stores bile that was produced in the liver. When activated it will secrete this bile into the Duodenum. This bile will help emulsify fats to create more surface area so that hydrolytic lipases (fat enzymes) can break the fat down chemically.

You Can’t Live without your LIVER! Produces Bile? Converts Carbohydrates to control blood sugar levels. Detoxifies the blood? Makes lots of vital Plasma Proteins? Stores Iron and Fat Soluble Vitamins – ADEK. Helps break down nitrogenous metabolic wastes. Example : Ammonia  Urea Produces Cholesterol and regulates blood cholesterol levels.

DUODENUM GLANDS Exocrine glands of the DUODENUM put out: PeptiDase NucleosiDases Maltase – AKA -MalDASE Endocrine Glands - Secrete hormones: GIP - Gastric Inhibitory Peptide SECRETIN  Pancreas CCK – Cholecystokinin  Liver/Gallbladder

Fig. 12.11

Fig. 12.7 Controlling The Gut GIP – Gastric Inhibitory Peptide

Fig. 12.12

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