What happens where? STARCH to MALTOSESALIVARY AMYLASE REACTANT/PRODUCTENZYME PROTEINS to PEPTIDES LIPASE Chymo/trypsin LIPIDS to FAs & GLYCEROL PROTEINS to PEPTIDES PROTEINS to A.ACIDS PEPSIN Carboxypeptidase LIPIDS to FAs & GLYCEROL LIPASE

MALTOSE to GLUCOSE SUCROSE to GLUCOSE + FRUCTOSE LACTOSE to GLUCOSE + GALACTOSE PEPTIDES to AMINO ACIDS MALTASE SUCRASE LACTASE PEPTIDASE

LUMEN MUCOSA – layer closest to the lumen. First layer is epithelial cells with goblet cells that secrete a mucus to protect epithelium from enzymes. Beneath this is connective tissue SUBMUCOSA – made up of Connective tissue. Here Blood vessels and nerves lie & fibrous proteins (elastin) MUSCULARIS EXTERNA – Two bands of muscle lie here (longitudinal & circular).- this aids peristalsis & mixes food. SEROSA – thin layer of Connective tissue 4 LAYERS !

We are going to look at the following areas of the digestive system in more detail: The mouth and the oesophagus The stomach The liver and pancreas The small intestine The colon

MASTICATION – chewing food using molars & premolars. 3 pairs of Salivary glands release saliva. Soluble materials dissolve. Starch to Maltose (S.Amylase) C & L muscles Help to swallow Food. Bolus enters the Stomach.

Cardiac sphincter – opens To let bolus into stomach Pyloric sphincter – opens to let bolus into the duodenum CHYME

A Gastric Pit Creates a very folded surface which secretes gastric juices. Creates a very folded surface which secretes gastric juices. Gastric juices are approx. pH 1.

A Gastric Pit Parietal (oxyntic) cells release HCL. pH 1 kills lots of Bacteria. Chief cells release Pepsinogen. Pepsinogen is an inactive enxyme

HCL + pepsin work together to convert inactive PEPSINOGEN to PEPSIN A Gastric Pit Gastric juice also contains gastric LIPASE Gastric mucus is produced to protect epithelium from low pH Little absorption occurs in the stomach

LIVER GALL BLADDER PANCREAS STOMACH BILE DUCT THE DUODENUM – PANCREAS & LIVER

THE DUODENUM – PANCREAS & LIVER Pyloric sphincter relaxes – chyme leaves the stomach. The liver prdc. bile This is stored in the gall bladder. Bile moves down the bile duct and into the Duodenum.

THE DUODENUM – PANCREAS & LIVER What is bile? Salts: Sodium glycocholate Sodium taurocholate Salts are derived from cholesterol Ions: Hydrogencarbonate ions

These neutralise the acidic Chyme from the stomach Salts These emulsify fats Droplets to single fats pH 1 pH 7

THE DUODENUM – PANCREAS & LIVER PANCREAS Pancreas has a dual function…… ……as an ENDOCRINE & EXOCRINE gland

Pancreas as an ENDOCRINE gland. Pancreatic juice is Made in the pancreas and secreted into the duodenum Enzymes: TRYPSIN CHYMOTRYPSIN ENTEROKINASE LIPASE AMYLASE CARBOXYPEPTIDASE

They are initially release in their inactive forms TRYPSINOGEN CHYMOTRYPSINOGEN TRYPSIN & CHYMOTRYPSIN - are both proteases ENTEROKINASE catalyses the following reactions TRYPSINOGEN to TRYPSIN CHYMOTRYPSINOGEN to CHYMOTRYPSINOGEN Pancreatic juice also contains HYDROGENCARBONATE ions, this keeps the pH at NEUTRAL.

THE SMALL INTESTINE – 5m long THE SMALL INTESTINE – Composed of 3 parts: (1) DUODENUM (25cm (2) JEJUNUM (2m) (3) ILEUM (2.75m)

THE SMALL INTESTINE – 5m long Villi Crypts of Lieberkuhn Goblet cells Paneth cells LUMEN

One villus has lots of MICROVILLI MICROVILLI: 1 µ m long and 0.1 µ m wide

GOBLET CELL secretes mucus Artery, vein & lymphatic Capillary are all important In removing digested food.

Crypt of Lieberkuhn Goblet cells are found here So are ……….. PANETH cells. Phagocytosis?

Two types of digestion in the Small Intestine Occurs in the LUMEN Pancreatic juices continue to work. Occurs on the surface of VILLI. Many epithelial cells have enzymes embedded into their plasma membranes. Some enzymes become adsorbed into the GLYCOCALYX

The final products of digestion are: AMINO ACIDS FATTY ACIDS GLYCEROL MONOSACCHARIDES We have moved from large insoluble polymers to small soluble monomers All of these products then cross the plasma membrane of the villi and then enter blood lymphatic capillaries Diffusion, active transport and facilitated diffusion all have a role