DIGESTIVE SYSTEM AND BODY METABOLISMChapter 14

ANATOMY Two main parts

Alimentary canal Performs the following

functions: Ingestion Digestion Absorption Defecation

Accessory digestive organs Teeth Tongue Digestive glands

ALIMENTARY CANAL AKA Gastrointestinal (GI) Tract

Continuous, hollow tube winding through the ventral cavity

Open at both ends Contains the following organs:

Mouth Pharynx Esophagus Stomach Small and Large Intestines

PARTS OF ALIMENTARY CANAL Oral Cavity

Lined by mucous membrane Teeth: mechanical digestion Salivary glands: moisten food so it can be swallowed Tongue: helps mix saliva with food; involved in mechanical

digestion Uvula: “dangly thing;” projection of the soft palate

Pharynx Connects digestive and respiratory systems

Epiglottis: flat of skin that closes to prevent food from going into trachea Walls composed of two layers of muscle

Inner layer-longitudinal Outer layer-circular (constrictor muscles) Alternating contractions push food into esophagus (below)

Called peristalsis

ORAL CAVITY ANATOMY

PARTS OF ALIMENTARY CANAL, CONT. Esophagus

Runs from pharynx to stomach About 10 inches long

From esophagus to large intestine, walls are made of four layers: Mucosa Submucosa Muscularis externa Serosa

MUCOSA // SUBMUCOSA Innermost layer Moist Functions in secretion

and absorption Epithelium and

smooth muscle Esophagus: stratified

squamous epithelium Resists friction

The rest: simple columnar epithelium Better for absorption

Beneath mucosa Made of connective

tissue Contains blood

vessels, nerves, lymphatic tissue

MUSCULARIS EXTERNA // SEROSA Muscular layer Contains two layers

Circular and Longitudinal muscles

Outermost layer Serous membrane

Layer of flat fluid-producing cells Visceral peritoneum Visceral peritoneum

continuous with parietal peritoneum Lines

abdominopelvic cavity via mesentery

ALIMENTARY CANAL-BASIC STRUCTURE

STOMACH C-shaped; on LEFT side of abdominal cavity Has four regions

Cardiac region: where food enters from esophagus Lower esophgeal sphincter: prevents backflow into

esophagus Fundus: expanded part lateral to cardiac region Body: middle part; largest part Pylorus: funnel-shaped; next to small intestine

Pyloric sphincter: valve that controls emptying of stomach Inside curve: lesser curvature Outside curve: greater curvature Folds in stomach lining: rugae

STOMACH, CONT. Stomach is site of secretion Glands:

Parietal cells-secrete HCl Chief cells-secrete pepsinogen Mucous glands;coat inside to protect from HCl

Gastric ulcer: erosion of mucous layer/lining of stomach

Perforated ulcer: hole in stomach Most digestive activity is in pylorus

After processing, food is called chyme (looks like thick cream)

SMALL INTESTINE The major digestive

organ Large muscular tube,

divided into 3 sections: Duodenum

10 inches long Attaches to stomach

Jejunum About 8 feet long

Ileum About 12 feet long

SMALL INTESTINE, CONT. Location of most

chemical digestion Pyloric sphincter

controls food movement

Villi Fingerlike projections

of mucosa Increase surface area

for absorption Microvilli Lacteal

LARGE INTESTINE Larger in diameter but shorter in length Functions:

Water absorption Elimination of wastes (feces)

Subdivisions: Cecum

Sac-like; appendix is attached Good location for bacteria growth/inflammation

Colon Ascending (up); Transverse (across); Descending

(down); sigmoid colon; rectum; anal canal Anal canal: contains voluntary and involuntary

sphincters

ACCESSORY ORGANS Pancreas

Pink, triangular Produces enzymes to

break down food Produces hormone insulin

Liver Largest gland in the

body Under diaphragm,

toward right side of body

Produces bile Yellowish-green solution

that helps digest fats Emulsification (acts like

detergent) Breaks large fat globules

into smaller ones Gallbladder

Bile is stored here until it is needed

NUTRIENTS Carbohydrates

Sugars and Starches Come mainly from plants

Sugars-from fruits, sugar cane, milk Starches-from grains, legumes, root veggies

Cellulose-in plant cell walls Not digested by humans Provides fiber, helps defecation

Lipids Fats

Saturated-animal products and coconut Unsaturated-seeds, nuts, vegetable oils

NUTRIENTS, CONT. Proteins

Made of amino acids Found in animal products

Complete proteins-eggs, milk, meat Incomplete proteins-beans, peas, nuts, cereals

Missing some essential amino acids Vitamins

Required in small amounts Need a balanced diet to have all necessary

vitamins Minerals

Inorganic substances such as calcium, sodium, potassium, etc.

METABOLISM Term referring to all chemical reactions in the

body Includes:

Catabolism Breaking down

Anabolism Building larger molecules

Energy is released and captured to make ATP which is used for all the body’s activities

ENERGY BALANCE Energy can’t be created or destroyed-it can only change

form Energy intake = Energy output*

Energy output = heat + work + storage) Storage isn’t important except in growth periods/fat deposit

Energy in food measured in kilocalories (kcal)

Basal Metabolic Rate (BMR) Amount of kcal needed by body when it is at rest

Total Metabolic Rate (TMR) Total amount of kcal needed by body to sustain all

ongoing activities When total calories = TMR body weight is constant