Transcript Digestive System

DIGESTIVE SYSTEM
ORGANS
DIGESTIVE SYSTEM BROKEN DOWN INTO 2 PARTS
1. Alimentary Canal – gastrointestinal (GI
Tract) – Path that food travels
2. Accessory Organs
GI Tracts
Accessory Organs
Oral
Cavity
Ascending
Colon
Pharynx
Transverse
Colon
Esophagus
Stomach
Duodenum
Descending
Colon
Jejunum
Sigmoid
Colon
Ileum
Rectum
Cecum
Anus
Tongue
Pancreas
Liver
Gallbladder
Parotid Gland
Appendix
Sublingual Gland
Submandibular
Gland
Uvula
Lingual Frenulum
MOUTH
Palate:
Hard
Soft
Uvula
Tongue
SALIVARY GLANDS
Cleanses Mouth
Important for Taste
Moistens food
Contains Enzymes
MAJOR SALIVARY GLANDS
•Parotid gland
•Submandibular
gland
•Sublingual gland
The average person
produces 1000-1500
ml a day
TEETH
Masticate = to chew
Baby teeth (deciduous)
Full set = 20 teeth
Permanent teeth = 32 teeth
Incisors
Canines
Premolars/molars
PHARYNX
Longitudinal & Circular layers of
Muscles  Peristalsis
Peristalsis - is a radially symmetrical
contraction and relaxation of muscles
that propagates in a wave down a
tube
ESOPHAGUS
Propels food using muscles (Peristalsis)
STOMACH
Mostly Protein Digestion
No Absorption***
Mechanically & Chemically Digested
Into Chyme
Gastric glands produce gastric juice:
acidic
Walls of Stomach lined with mucus so
the acid doesn’t “digest itself”
CHYME
Substance in the stomach that is formed from
food and enzymes
PROBLEMS OF THE STOMACH
Ulcers: a hole in
the mucus lining of
the stomach
Heartburn (acid
reflux): contents of
stomach move into
esophagus
SMALL INTESTINE
SM. INTESTINE
Chemical digestion of carbohydrates,
proteins, nucleic acids, & fats
Done with enzymes from pancreas and bile
(formed in liver)
Pancreatic duct and bile duct empty into
duodenum – where enzymes empty into.
LARGE INTESTINE
Function:
To absorb water
Eliminate residue as feces
Absorb vitamins produced by
bacteria
Role of Bacteria:
Digest some nutrients
Produce vitamins
Produce gas
ACTION OF L. INTESTINE
Peristalsis
Mass Peristalsis: a strong wave that pushes contents
towards rectum
Problems:
Diarrhea
Constipation
ACCESSORY ORGANS - PANCREAS
Releases enzymes into duodenum
Has an endocrine function
ACCESSORY ORGANS - LIVER
Produces bile; leaves through
common hepatic duct
Bile: part waste produce, part
digestive secretion (mechanical
digestion of lipids)
OTHER LIVER FUNCTIONS
Metabolism of carbs, lipids, and proteins
Processing of drugs and hormones
Excretion of bilirubin (from hemoglobin of old
RBCs)
ACCESSORY ORGANS - GALLBLADDER
Releases bile in response
to fatty food entering
duodenum
Location: underside of
liver
Gallstones
STEPS OF DIGESTION
DIGESTION
Major functions of the digestive tract are digestion and
absorption
ESSENTIAL ACTIVITIES OF THE GI TRACT
Ingestion
Propulsion
Food Breakdown – mechanical digestion
Food Breakdown – chemical digestion
Absorption
Defecation
1. INGESTION
•Food must be placed into the mouth before it
can be acted on.
•Active, voluntary process
2. PROPULSION
•In order for food to be processed by different organs,
they must be propelled from one organ to the next.
•Example:
•Swallowing – depends on the propulsive process called peristalsis
•Peristalsis – involuntary and involves alternating waves of contraction and
relaxation of the muscles in the organ walls
3. FOOD BREAKDOWN – MECHANICAL
DIGESTION
•Mixing of food in the mouth by the tongue
•Churning food in stomach
•Segmentation – propels foodstuffs through the
small intestine
•Prepares food for further degradation by enzymes
4. FOOD BREAKDOWN – CHEMICAL DIGESTION
•Sequence of steps which large food molecules
are broken down to their building blocks by
enzymes
5. ABSORPTION
•Transport of digested end products from the lumen of the
GI tract to the blood or lymph
•For absorption to occur, digested foods must first enter the
mucosal cells by active or passive transport processes
•Small intestine is major site of absorption
6. DEFECATION
•Elimination of indigestible residues from the GI tract
via the anus to form feces
NEURAL & HORMONAL CONTROL
CEPHALIC PHASE
•Occurs before food enters the stomach,
especially while it is being eaten
•Brain is activated by smell, sight,
thought, and taste of food
•Neurons to salivary glands and gastric
glands/stomach muscles
•Autonomic Nervous System
GASTRIC PHASE
STIMULUS: FOOD IN STOMACH
•Neural:
•Stretch receptors activated.
Impulse to neurons in
submucosa
•Triggers:
•Gastric gland production
and causes peristalsis
•Hormonal:
•Food triggers release of
gastrin. Goes in the blood.
•Triggers:
•Gastric gland juices
•Sphincter to prevent acidreflux
•Stomach muscles
•Relaxes lower stomach
sphincter
INTESTINAL PHASE
STIMULUS: FOOD IN INTESTINE
•Neural:
•Hormonal:
•Stretch receptors to medulla
•Cholecytokinin (CCK):
oblongata
stimulates pancreatic
•Sympathetic nerves to stomach
juice/squeezes
cause:
gallbladder
•Decreased stomach movement &
increase contraction of pyloric –
bottom – sphincter (delays
stomach emptying)