Chapter 24 Digestion Flashcards
Gastrointestinal tract organs
Mouth Pharynx Esophagus Stomach Sm. Intestine Lg. Intestine
Accessory organs
Teeth Tongue Salivary Glands Liver Gallbladder Pancreas
Functions of Digestive System
Ingestion: eating Secretions: acids, buffers (7L/day) Motility: mixing, propulsion Digestion: mechanical and chemical Absorption: nutrients, fluids Defecation: removal of metabolic waste
Mucosa
Inner lining of Gi tract
Contains:
Epithelial cells: absorbs nutrients and contains enteroendocrine cells
Lamin propria: areolar connective tissues, blood vessels and lymphatic vessels. Contains MALT
Muscularis mucosa: smooth muscle fibers increases surface are
Submucosa
Contains collagenous fibers, nerves and blood vessels.
Areolar connective tissue binds the mucosa to the muscularis.
Vascular and contains the submucosal plexus, or the plexus of meissner
Muscularis
2 types of smooth muscle: inner circular and outer longitudinal fibers.
Contains the myenteric plexus/ plexus of Auerbach
- mostly controls GI motility
Serosa
Superficial layer of the GI tract, suspended in the abdominopelvic cavity
Has a serous membrane that’s composed of areolar connective tissue and simple squamous epithelium (mesothelium)
Epithelial portion is also called visceral peritoneum
Peritoneal Folds
Largest serous membrane in the body
Divided into Parietal peritoneum and visceral peritoneum/serosa
Mesentery
binds the jejunum and ileum (sm. intestine) to the posterior abdominal wall
Mesocolon
binds the transverse and sigmoid colon (lg. intestine) to the posterior abdominal wall
Salivary Glands
3 major pairs 1. Parotid glands (Stensen's duct) 2. Submandibular glands (Wharton's duct) 3. Sublingual glands (Rivinus' ducts) Both sympathetic and parasympathetic innervation
Saliva
Salivary amylase begins to breakdown starch in the mouth
Teeth
Also called dentes. Composed of:
- crown
- neck
- dentin
- enamel
- pulp cavity
Pharynx
Nasopharynx: respiration
Oropharynx: digestive and respiratory functions
Laryngopharynx: digestive and respiratory functions
Esophagus
Secretes mucus and transports food into the stomach
- Elevation of larynx causes the upper esophageal sphincter to relax, allowing the bolus to enter the esophagus
Peristalsis control movement of the esophagus (swallowing).
Lower esophageal sphincter is also called gastroesophageal or cardiac sphincter
Stomach
J shaped. Connects the esophagus to the duodenum
Functions as a mixing area and holding reservoir.
Digestion of proteins and triglycerides begins in stomach, breakdown of starch continues in stomach.
Up to 6.4 L of liquid food
Enzymes in the stomach
Pepsin: protein digesting enzyme
Gastric lipase: triglycerdie digesting enzyme
Pancreatic lipase: fat digesting enzyme.
4 Regions of Stomach
- Carida
- Fundus: storage of food
- Body: mixing
- Pyloric Part
4a. Pyloric antrum: connects to body of stomach (food mixing)
4b. Pyloric canal (leads to pylorus)
4c. Pylorus: connects to duodenum
Gastric Gland
3 types of exocrine gland cells
Mucous neck cells, chief cells, parietal cells.
Secretion from all 3 = 2-3L/day.
Functions of the Pancreas
Can produce 1200-1500 ml of pancreatic juice/day.
Pancreatic amylase: a starch digesting enzyme.
Enzymes that digest protein:
- trypsin
- chymotrypsin
- carboxypeptidase
- elastase
Principle trigylceride:
- pancreatic lipase
- RNA and DNA digesting enzymes called ribonuclease and deoxyribonuclease
Anatomy of the Pancreas
Head Body Tail Pancreatic duct (wirsung) Hepatopancreatic ampulla (ampulla of vater) Major duodenal papilla Accessory duct (duct of Santorini)
Gallbladder
Anatomy - fundus - body - neck Function - storage of bile
Functions of the Liver
Emulsification: breakdown of large lipid globules into small droplets
Absorption
Bile Storage (sphincter of the hepatopancreatic ampulla)
Carb/lipid/protein metabolsim
Vitamin storage
Phagocytosis by Kuffer cells and immune cells
Anatomy:
Divided into two lobes by the falciform ligament (l and r)
Hepatic Blood Flow
Oxygenated blood from hepatic artery and nutrient-rich, deoxygented blood from the hepati portal vein Hepatic sinusoids Central vein Hepatic vein Inferior Vena Cava Right Atrium
Functions of the Large Intsetine
Haustral churning: contraction and squeezing the contents into the next houstrum.
Peristalsis: slower wave of contraction
Mass peristalsis: occurs in the transverse colon and has stronger waves.
Anatomy of the Large Intestine
Extens from the ileum to the anus. 4 Principal regions 1. Cecum 2. Colon 3. Rectum 4. Canal Ileocecal sphincter, cecum, appendix and mesoappendix (mesentery of the appendix).
