Digestive System Flashcards
Absorption
Movement of nutrients into the bloodstream
Ingestion
Taking in food
Defecation
Rids the body of indigestible waste
Mechanical digestion
Breaking down physically
Chemical digestion
Break down chemically
Alimentary canal (GI tract)
Continuous hollow tube that runs from mouth to anus
Accessory digestive organs
Organs that the food doesn’t directly enter but helps with digestion
Ex: liver, pancreas
Organs of the alimentary canal
Mouth to pharynx to esophagus to stomach to small intestine to large intestine to anus
Mouth anatomy: lips
Protect anterior opening
Mouth anatomy: cheeks
Form the lateral walls
Mouth anatomy: hard palate
Forms anterior roof
Mouth anatomy: soft palate
Forms posterior roof
Mouth anatomy: uvula
Fleshy projection of the soft palate
Mouth anatomy: tongue
Attached at hyoid bone and styloid processes of the skull and by the lingual frenulum to the floor of the mouth
Mouth anatomy: tonsils
Palatine lingual
Pharynx physiology
Serves as a common passageway for air and food
Pharynx physiology
Serves as a common passageway for air and food
Esophagus: Anatomy
About 10 in long
Runs from pharynx to stomach through the diaphragm
Esophagus: physiology
Conducts for peristalsis (slow rhythm squeezing)
Passageway for food only (respiratory system branches off after the pharynx)
Stomach anatomy
Located on the left side of the abdominal cavity
Food enters at the cardiac sphincter (valve)
Food empties into the small intestine at the pyloric sphincter (valve)
Regions of the stomach
Cardiac region
Fundus
Body
Pylorus
Cardiac region
near the heart
Fundus
Expanded portion lateral to the cardiac region
Body
Mid portion
Layers of peritoneum attached to the stomach
Lesser omentum
Greater omentum
Lesser omentum
Attaches to the liver to the lesser curvature
Greater omentum
Contains fat to insulate, cushion, and protect abdominal organs
Attaches the greater curvature to the posterior body wall
Has lymph nodules containing macrophages
Stomach physiology
Temporary storage tank for food Site of food breakdown Chemical breakdown of proteins begin Delivers chyme (processed food) to the small intestine
Structure of the stomach mucosa
Mucosa is simple columnar epithelium Mucous neck cells Gastric glands Chief cells Parietal cells Enteroendocrine cells
Mucosa neck cells
Produce a sticky alkaline mucus
Gastric glands
Situated in gastric pits and secrete gastric juice
Chief cells
Reduce proteins digesting enzymes (pepsinogens)
Parietal cells
Produce hydrochloric acid
Enthroned octane cells
Produce gastrin
Small intestine
The bodies major digestive organ
Site of nutrient absorption into the blood
Muscular tube extending from the pyloric sphincter to the ileocecal valve
Suspended from the posterior abdominal wall by then mesentiery
Subdivisions of the small intestine
Duodenum
Jejunum
Ileum
Duodenum
10 inches long
Attached to the stomach
Curves around a hold of the pancreas
Jejunum
8 feet long
Attaches anteriorly to the duodenum
Ileum
12 feet long
Extends from jejunum to large intestine
Chemical digestion begins in the small intestine
Enzymes are produced by intestinal cells and the pancreas
Pancreatic ducts carry enzymes to the small intestine
Bile, formed by the liver, enters via the bile duct
Small intestine anatomy
Structural modifications that increase surface area
Micro villi
Villi
Microvilli
Tiny projections of the plasma membrane (create a brush border appearance)
Villi
Fingerlike structures formed by the mucosa
Large intestine
Large in diameter, but shorter in length, then the small intestine
Frames the internal abdomen
Large intestine anatomy
Cecum: saclike first part of the large intestine
Appendix
Appendix
Accumulation of lymphatic tissue that sometimes becomes inflamed (appendicitis)
Hangs from the Cecum
Ascending colon
Travels up right side of abdomen
Transverse colon
Travels across the abdominal cavity
Descending colon
Travels down the left side
Sigmoid colon
Enters the pelvis
Anus
Opening of the large intestine
External anal sphincter
Formed by skeletal and under voluntary control
Internal anal sphincter
Formed by smooth muscle
Anal sphincters
These sphincters are normally closed except during defecation
Large intestine anatomy continued
No villi present
Goblet cells produce alkaline mucus which lubricates the passage of feces
Accessory digestive organs
Liver Teeth Gallbladder Pancreas Salivary glands
Teeth function
Masticate (chew) food
Humans have two sets of teeth
Deciduous
Permanent
Deciduous teeth
Baby or milk teeth
20 teeth fully formed by age two
Permanent teeth
Replace deciduous teeth between six and 12
Full set is 32 teeth that some people don’t have wisdom teeth
If they do emerge, the wisdom teeth appear between ages 17 and 25
Classification of teeth
Incisors: cutting
Premolars: grinding
Canines: tearing or piercing
Molars: grinding
Salivary glands
Three pairs of salivary glands empty secretion into the glands
Parotid
Submandibular
Sublingual
Saliva
Mixture of mucus mad serous fluid
Helps to form a food bolus
Contains salivary amylase to begin starch digestion
Dissolves chemicals so they can be tasted
Pancreas
Found posterior to the parietal peritoneum
Extends across the abdomen from spleen to duodenum
Produces a wide spectrum of digestive enzymes that break down all categories of food
Enzymes are secreted into the duodenum
Hormones produced by the pancreas insulin
Liver
Largest gland in the body
Located on the right side of the body under the diaphragm
Consists of four lobes suspended from the diaphragm and abdominal wall by the falciform ligament
Connected to the gallbladder via the common hepatic duct
Bile
Produced by cells in the liver
Bile composition
Bile salts Bile pigments (mostly bilirubin from the breakdown of hemoglobin) Cholesterol Phospholipids Electrolytes
Bile function
Emulsify (break apart) fats by physically breaking fat globules into smaller ones
Gallbladder
When no digestion is occurring, bile backs up the cystic duct for storage in the gallbladder
Sac found in hollow fossa (hole) of liver
When digestion of fatty food is occurring, bile is introduced into the duodenum from the gallbladder
Gallstones are crystallized cholesterol which can cause blockages
Propulsion
Moving foods from one region of the digestive system to another
Peristalsis
Alternating waves of contraction and relaxation that squeezes food along the GI tract
Chemical digestion
Enzymes break down food molecules into their building blocks
Each major food group uses different enzymes
Carbs broken to simple sugars, proteins to amino acids, fats to fatty acids and alcohol
Absorption
End products of digestion are absorbed in the blood or lymph
Food must enter mucosal cells and then into blood or lymph capillaries
Defection
Elimination of indigestible substances from the GI tract in the form of feces
Digestive activities of the mouth: chemical
Food mixed with saliva
Starch is broken down into maltose by salivary amylase
Hydrochloric acid
Makes the stomach contents very acidic
Acidic pH
Activates pepsinogen to pepsin for protein digestion
Provides a hostile environment for microorganisms
Protein digestion enzymes
Pepsin: an active protein digesting enzyme
Rennin: works on digesting milk protein in infants, not adults
Alcohol and asprin are the only items absorbed into the stomach
Propulsion in the stomach
Food must first be well mixed
Stomach empties in 4-6 hours
Rippling perstalsis
Occurs in the lower stomach
The pylorus
Real eases chyme into the small intestine (30 mL at a time)
Digestion in the small intestine
Help complete digestion of starch (pancreatic amylase)
Alkaline content neutralizes acidic chyme
Carry out about half of all protein digestion
Digest fats using lipases from the pancreas
Food breakdown and absorption in the large intestine
No digestive enzymes are produced
Resident bacteria digest remaining nutrients
Release gases
Water is absorbed
Remaining materials are eliminated via feces
Carbohydrates
Most are derived from plants
Exceptions: lactose from milk and small amounts of glycogens from meats
Major nutrients
Carbohydrates
Lipids proteins
Water
Minor nutrients
Vitamins
Minerals
Nutrient
Substance used by the body for growth, maintenance, and repair
Lipids
Saturated fats from animal products
Unsaturated fats from nuts, seeds and vegetable oil
Cholesterol from egg yolk, meats and milk products
Proteins
Complete proteins: contain all essential amino acids
Most from animal products
Legumes and beans also have proteins, but are incomplete
Vitamins
Most used as coenzymes
Found in all major food groups
Minerals
Play many roles in the body
Most mineral rich foods are vegetables, legumes, milk and some meats
Lysozyme
Enzyme in saliva that fights infection by digesting the cell walls of bacteria
Alimentary canal
One way tube that passes through the body
Bile
Fluid that prepares fat molecules to be broken down by enzymes
Gastric glands
Microscopic structure that releases a number of substances into the stomach
Islets of langerhans
Small clusters of cells, some of which produce insulin, that are located inside the pancreas
Mouth
Alimentary canal begins
Glucagon
Hormone that enables the body to break down glycogen and fats, and release sugars in the blood
Villus
Projection in the lining of the small intestine
Peristalsis
Contractions of smooth muscle that move food through the alimentary canal
Small intestine
Part of the digestive system that consists of the duodenum, jejunum, and ileum
Region of the digestive system where most of the chemical work of digestion takes place
Esophagus
Tubelike structure through which food passes btwn the mouth and stomach
Large intestine
Region of the digestive system where in digested wastes are prepared for removal from the body
Pepsin
Protein digesting enzyme produced by gastric glands
Insulin
Polypeptide hormone that enables the body to convert sugar in the bloodstream into stored glycogen and fat
Salivary gland
Structure that produces a fluid that helps to moisten food
Pancreas
Gland located just below the stomach that produces enzymes and other substances essential for digestion
Stomach
Large sac that mixes food with acids and enzymes to produce chyme
Liver
Gland that produces bile
Amylase
Enzyme in saliva that breaks the chemical bonds in starches
