Lect 17Digestive

Gastrointestinal TractAccessory Organs

Intro to Anatomy , Physiology

and Nutrition

Digestive Tract = ___________

• Mouth

• Pharynx

• Esophagus

• Stomach

• Small Intestine

• Large Intestine

• Anus

Accessory Organs

• Teeth and salivary glands

• Liver/gall bladder

• Pancreas

• Mesenteries

Alimentary Canal - Characteristic Cross Section– __________ = Passage down the middle– Mucosa– Submucosa

• What kind of tissue?• What is found in this layer?

– Muscle layer– Serosa = ? Type of membrane

____________

Functions of the Digestive System• The process of taking foods and liquid into the

mouth: • Ingestion• The release of water, acid, buffers, and enzymes

by cells and accessory organs into the lumen.• Secretion• Alternating contraction and relaxation of smooth

muscle.• Peristalsis Mixing and propulsion• Mechanical and chemical break down of organic

material into small molecules.• Digestion

Mouth

• Cheeks: lateral walls– buccinator muscles, bucal fat pads

– Non-keratinized stratified squamous epithelium

– Lips attach to gum: labial frenulum (a midline fold)

• Vestibule: space between lips and gums (gingiva)/teeth

• Oral cavity proper – from gums and teeth to Fauces

Oral Cavity• Floor:

– Mylohyoid muscle– Tongue

• frenulum

• Palate:– Hard Palate: palantine bones + part of maxilla– Soft Palate: + Uvula – close oral cavity

nasopharynx

• Tonsils:– Palatine: either side of tongue– Lingual : near base of tongue at hyoid bone– Pharyngeal: = adenoids – posterior wall of

pharynx

Teeth• Fours types:

– Incisors– Canines– Premolars– Molars

• Primary teeth: deciduous – ‘baby teeth’• Adult teeth

– dental formula: number of teeth of each type in one half of each jaw reading from the front (incisors) to back (molars)

• Humans Adults: 2123/2123

Tortora & Grabowski 9/e 2000 JWS

Salivary Glands

• Parotid below your ear and over the masseter• Submandibular is under lower edge of mandible• Sublingual is deep to the tongue in floor of mouth• All have ducts that empty into the oral cavity

Pharynx – 3 regions:NasopharynxOropharynx

Laryngopharynx

• Swallowing:

• What prevents food from entering nasal cavity:

• What temporarily seals oral cavity/pharynx?

• What closes opening to respiratory passage?

• Peristaltic wave pushes _______ down __________.

The Esophagus

• Anatomy– A collapsible 10 inch

long muscular tube.

• Functions – Secrete mucus and

transport food from the pharynx to the stomach.

• Rhythmic waves of muscle contraction?

(Peristalisis).

• Pierces the diaphragm at hiatus– hiatal hernia or

diaphragmatic hernia

Peritoneum

• visceral layer covers organs

• parietal layer lines the walls of body cavity

• Peritoneal cavity– potential space containing a bit of

serous fluid

Greater Omentum- fatty apron: covers transverse colon and small intestine.

• Falciform Ligament: Suspends liver from anterior wall of abdomen/diaphragm

• Lesser Omentum: suspends stomach and duodenum from liver

• Mesentary Proper: Extends from dorsal wall of abdominal cavity, suspends small intestine

• Mesocolon: binds transverse and sigmoid colon to dorsal abd. wall

Falciform Ligament

Lesser Omentum

Greater OmentumMesentary

Proper

Mesocolon

• Which side is it on? • Size when empty?• Parts of stomach?• Structure of its walls?

• Smooth muscle layers• rugae• Gastric pits

• What digestive processes occur here

• Associated mesenteries?• Semifluid contents are

known as?

Gastric Pits and Gastric Glands

• Gastric Pits: shallow depressions of gastric mucosa

• Gastric Glands: – Open to gastric pits– Endocrine and exocrine cells in walls – Exocrine secretions gastric juice

• Protects walls of stomach

• Acid environment activates pepsinogen

• Absoption o f B12 in small intestine

• Initiates protein breakdown

• Hormonal activity initiates smooth muscle action and secretion of gastric juice

• What stimulates secretion of Gastrin?

Secretion of gastric juice – parasympathetic involvement – sensory stimuli

• Small Intestine

• Three parts

• Digestive processes– Absorption of lipids

• Special adaptations – functions

• Support

Absorption in Small Intestine

• Absorption of Lipids

• Bile salts act to emulsify

• Fatty acids + glycerol at villi– Intermediate metabolic conversions

chylomicrons – protein encased structures enter blood stream

– Delivered to• tissues as LDL• Liver as HDL

– Bile salts feces

Where will the absorbed nutrients go?

Pancreas- Endocrine/Exocrine

• Endocrine – Islet tissues

• Exocrine – acinar cells via pancreatic duct ?? (where)– Pancreatic juice:

• Pancreatic amylase• Trypsin• Lipase etc.• Releases bicarbonate ions – neutralizes chyme

– Regulation via • secretin from duodenal epithelial tissues• Cholecystokinin

Liver

• Lobes divided into lobules

• Blood from portal vein sinusoids central canal

• Multiple functions– Blood glucose glycogen blood glucose– Lipid oxidation

– Formation of urea from NH2

– Deamination of aa– Storage – Production of bile

• Bile and the Gall Bladder

• Bile– Bile salts– Others– Emulsification of lipids– Released as fatty substance enter lumen of

duodenum– Cholecystokinin (CCK) stimulates contrations

of gall bladder

• Large Intestine

• Regions– Cecum

• Veriform appendix

– Colon – 4 regions– Rectum– Anal canal

• Internal & external anal sphincters

• Functions

Symbiotic Bacteria Reside in the Colon

• Numbers- about 50 species.• Fecal component- accounts

for about 1/3 the total weight of feces.

• They are nourished by undigested foods.

• Their metabolic processes produce gas.

• Some produce vitamins B and K.

• They decompose pigmented molecules, which give feces its brown color.

Nutrition

• Macronutrients – energy source– Calorie – measure of energy in foods

• Micronutrients – required for vital biochemical processes– Incl. vitamins & minerals

• Hydrolysis – initial step

• Essential nutrients

• Essential fatty acids– Required for synthesis of other forms in liver

• Linoleic acid

• Essential amino acids (8)– See table 15.8

• Complete vs partially complete proteins

• Issues with Fats and Cholesterol– 4x amt of energy in carbs– Does Cholesterol intake greatly impact risk of

heart disease?– What is the impact of intake of different kinds

of fats on arthrosclerosis – (linked to heart disease)?

– Trans fats?

• Carbohydrates – all are not the same

• Glycemic Index: impact/rate of change in blood glucose levels after ingestion

• Some examples of high vs. low glycemic index foods

• Impact of milling on glycemic index

• Vitamins

• Fat soluble

• Water-soluble– B complex– C (ascorbic acid)

The End.