Digestive SystemDigestive System

FunctionsFunctions

Ingestion Secretion Mixing and propulsion Digestion Absorption Defecation

Ingestion Secretion Mixing and propulsion Digestion Absorption Defecation

Digestive OrgansDigestive Organs

GI tract: Mouth, Pharynx, Esophagus,

Stomach, Small Intestine, Large Intestine, Anus

Accessory organs: Teeth, Tongue, Salivary glands, Liver,

Gallbladder, Pancreas

GI tract: Mouth, Pharynx, Esophagus,

Stomach, Small Intestine, Large Intestine, Anus

Accessory organs: Teeth, Tongue, Salivary glands, Liver,

Gallbladder, Pancreas

GI Tract LayersGI Tract Layers

Mucosa Epithelium - Strat. Squamous to Simple

Columnar Lamina propria Some smooth muscle

Submucosa - areolar Muscularis - skeletal higher, smooth

lower Serosa - visceral peritoneum

Mucosa Epithelium - Strat. Squamous to Simple

Columnar Lamina propria Some smooth muscle

Submucosa - areolar Muscularis - skeletal higher, smooth

lower Serosa - visceral peritoneum

PeritoneumPeritoneum Largest serous membrane Parietal and visceral Five major folds:

Contain adipose tissue Anchor major organs Contain blood vessels and lymph

nodes Greater Omentum and Mesentary

as examples

Largest serous membrane Parietal and visceral Five major folds:

Contain adipose tissue Anchor major organs Contain blood vessels and lymph

nodes Greater Omentum and Mesentary

as examples

Macromolecule ReviewMacromolecule Review

1. Carbohydrates - Mono- and Polysaccharides

2. Proteins - Amino acids form polypeptides

3. Lipids - Simple, complex, steroids4. Nucleic Acids

What kinds of enzymes break down each group?

1. Carbohydrates - Mono- and Polysaccharides

2. Proteins - Amino acids form polypeptides

3. Lipids - Simple, complex, steroids4. Nucleic Acids

What kinds of enzymes break down each group?

MouthMouth

Ingestion Mastication and moistening Beginning of chemical

digestion Movement of bolus to

oropharynx

Ingestion Mastication and moistening Beginning of chemical

digestion Movement of bolus to

oropharynx

Accessory Organs in Mouth

Accessory Organs in Mouth

Salivary glands - parotid, submandibular, sublingual

Tongue - papillae and lingual frenulum

Teeth 20 deciduous teeth, 32 permanent Incisors (4), canines (2), bicuspid (4),

molars (4-6?) per jaw

Salivary glands - parotid, submandibular, sublingual

Tongue - papillae and lingual frenulum

Teeth 20 deciduous teeth, 32 permanent Incisors (4), canines (2), bicuspid (4),

molars (4-6?) per jaw

MouthMouth Mechanical Digestion

Mastication - Tongue, teeth, saliva Bolus Chemical Digestion

Salivary Amylase - starch maltose, -dextrins

Lingual Lipase - Activated in stomach - Triglycerides F.A.s and Diglycerides

Saliva also used to: Destroy bacteria (Lysozyme, IgA) Lubricate food (mucus) Remove waste Aid gustation (water)

Mechanical Digestion Mastication - Tongue, teeth, saliva Bolus

Chemical Digestion Salivary Amylase - starch maltose, -

dextrins Lingual Lipase - Activated in stomach -

Triglycerides F.A.s and Diglycerides Saliva also used to:

Destroy bacteria (Lysozyme, IgA) Lubricate food (mucus) Remove waste Aid gustation (water)

EsophagusEsophagus

Laryngopharynx to stomach Upper esophageal sphincter (skeletal

muscle) Lower esophageal sphincter (cardiac)

Passes through diaphragm at esophageal hiatus

Laryngopharynx to stomach Upper esophageal sphincter (skeletal

muscle) Lower esophageal sphincter (cardiac)

Passes through diaphragm at esophageal hiatus

EsophagusEsophagus

Deglutition (Swallowing)

Peristalsis Wavelike

contractions Alternating

bands of muscle

Deglutition (Swallowing)

Peristalsis Wavelike

contractions Alternating

bands of muscle

StomachStomach

StomachStomach

Mechanical digestion Mixing waves - produce chyme and promote

gastric emptying

Chemical digestion Pepsin - proteins into smaller peptides HCl - partial denaturation

Absorbs some water, ions, Fas, some drugs and alcohol

Mechanical digestion Mixing waves - produce chyme and promote

gastric emptying

Chemical digestion Pepsin - proteins into smaller peptides HCl - partial denaturation

Absorbs some water, ions, Fas, some drugs and alcohol

Gastric GlandsGastric Glands

Gastric Juice HCl

kills microbes converts pepsinogen to pepsin

Pepsin - protein digestion Gastric lipase - Triglycerides Fas

and monoglycerides Mucous - protects lining

Gastric Juice HCl

kills microbes converts pepsinogen to pepsin

Pepsin - protein digestion Gastric lipase - Triglycerides Fas

and monoglycerides Mucous - protects lining

Gastric glandsGastric glands

PancreasPancreas

Endocrine and exocrine gland Pancreatic islets: insulin and

glucagon (and others) Acini: Pancreatic juice

Sodium bicabonate Enzymes to digest all four

macromolecule groups

Endocrine and exocrine gland Pancreatic islets: insulin and

glucagon (and others) Acini: Pancreatic juice

Sodium bicabonate Enzymes to digest all four

macromolecule groups

LiverLiver

Secretion of Bile Bile stored in gall bladder Used for:

Excretion of Bilirubin Emulsification of lipids by bile salts Easier absorption of lipids Excretion of drugs and hormones

Secretion of Bile Bile stored in gall bladder Used for:

Excretion of Bilirubin Emulsification of lipids by bile salts Easier absorption of lipids Excretion of drugs and hormones

Other Liver FunctionsOther Liver Functions1. Glycogen storage and glucose

release/production2. Lipid Metabolism3. Protein metabolism - ease conversion of

a.a., synthesize plasma proteins4. Detoxification5. Storage of vitamins/minerals6. Phagocytosis of old blood cells and some

bacteria7. Activation of vitamin D

1. Glycogen storage and glucose release/production

2. Lipid Metabolism3. Protein metabolism - ease conversion of

a.a., synthesize plasma proteins4. Detoxification5. Storage of vitamins/minerals6. Phagocytosis of old blood cells and some

bacteria7. Activation of vitamin D

Small IntestineSmall Intestine

90% of all absorption Aided by:

1. Length (10 ft avg)2. Villi (1 mm)3. Microvilli (1 um) - “Brush Border”

Monomers absorbed into capillaries or Lacteals

90% of all absorption Aided by:

1. Length (10 ft avg)2. Villi (1 mm)3. Microvilli (1 um) - “Brush Border”

Monomers absorbed into capillaries or Lacteals

Small IntestineSmall Intestine

Duodenum, jejunum, ileum Intestinal glands

Duodenal glands - alkaline mucus - why? Digestive enzymes along w/ pancreas

Circular folds - better absorption Villi

Absorptive cells Capillaries and lacteals Microvilli

Duodenum, jejunum, ileum Intestinal glands

Duodenal glands - alkaline mucus - why? Digestive enzymes along w/ pancreas

Circular folds - better absorption Villi

Absorptive cells Capillaries and lacteals Microvilli

Small IntestineSmall Intestine

Chemical Digestion Brush Border enzymes – all major

groups Intestinal Juices - water and mucus Pancreatic Juice, Bile and Intestinal

juice work in combination

Chemical Digestion Brush Border enzymes – all major

groups Intestinal Juices - water and mucus Pancreatic Juice, Bile and Intestinal

juice work in combination

Large IntestineLarge Intestine

Mechanical digestion Haustral churning - contraction following

distension Peristalsis Mass peristalsis - pushes contents into

rectum Chemical digestion by bacteria Absorption of water, ions, and some

vitamins

Mechanical digestion Haustral churning - contraction following

distension Peristalsis Mass peristalsis - pushes contents into

rectum Chemical digestion by bacteria Absorption of water, ions, and some

vitamins

DefecationDefecation

Feces formed in large intestine Water, Inorganic salts, Bacteria and their

products, Unabsorbed/Indigestible material, Epithelial cells

Defecation Reflex1. Rectum distended2. Stretch receptors spinal cord3. Parasymp contraction of colon and

rectum4. Internal anal sphincter opens5. External is voluntarily relaxed

Feces formed in large intestine Water, Inorganic salts, Bacteria and their

products, Unabsorbed/Indigestible material, Epithelial cells

Defecation Reflex1. Rectum distended2. Stretch receptors spinal cord3. Parasymp contraction of colon and

rectum4. Internal anal sphincter opens5. External is voluntarily relaxed

pHpH

Enzymes operate at optimal pH Saliva = 6.5 Gastric juice = 2 Pancreatic Juice = 7.1-8.2 Intestinal Juice = 7.6

pH adjusted by negative feedback (Buffers, Hormone release)

Enzymes operate at optimal pH Saliva = 6.5 Gastric juice = 2 Pancreatic Juice = 7.1-8.2 Intestinal Juice = 7.6

pH adjusted by negative feedback (Buffers, Hormone release)

HormonesHormones

Gastrin - gastric glands - gastric juice , gastric emptying , Sphincter control

Cholecystokinen (CCK) - s. Int - Pancreatic juice , Bile release , gastric emptying , satiation

Secretin - S. Int - Pancreatic Juice , Gastric Juice

Gastrin - gastric glands - gastric juice , gastric emptying , Sphincter control

Cholecystokinen (CCK) - s. Int - Pancreatic juice , Bile release , gastric emptying , satiation

Secretin - S. Int - Pancreatic Juice , Gastric Juice