Exam 4. Digestive system Flashcards
Digestive system
Digestion Stages
- Ingestion
- Digestion
- Absorption
- Compaction
- Defecation
Absorption: Mainly in the small intestine
Compaction: The materials we can’t digest or can’t absorb
Categories of the digestive system
- Accessory Organs
- Organs
Divided on these categories because of how they work
Organs of digestive system
These have contact with the food
- Mouth - Stomach - Rectum
- Pharynx - Large intestine - Anus
- Esophagus - Small intestine
Accessory Organs
Very important but do not have physical contact.
- Salivary glands
- Liver
- Gallbladder
- Pancreas
Layers of GI tract
- Mucosa
- Submucosa
- Muscularis Externa
- Serosa
Mucosa
- Lines the lumen
- Composed of 3 layers
1. Epithelium. Simple Columnar Epithelium
2. Fibrous connective tissue. Lamina propia
3. Muscularis mucosa. Thin layer of smooth muscle
Submucosa
- Blood vessels. Veins transports nutrients
- Lymphatic vessels. Absorbs lipids
- Nerves
Muscularis Externa
- Thick layer of smooth muscle
- 2 separate layer
1. Circular layer. Deeper one Squeezes and segments food
2. Longitudinal layer. Muscles are parallel. These produce contraction to push food down the line
Serosa
- Outer most layer
- Fibrous connective tissue that binds and supports GI tract.
Enteric Nervous System
- Regulates motility, secretion, blood flow
Like personal nervous system of GI tract - Independent of CNS, but CNS influences it
- Two networks: Submucosa plexus and Myenteric plexus
- Also regulates by hormones and paracrine
Omentum
- Protective and supportive membranes around the GI tract organs
- Lesser Omentum: Stomach-liver
- Greater omentum: Fatty apron. Covers the small and large intestine
Mesentery & Mesocolon
- Membranes that keep small and large intestine anchored or coiled in place.
- Mesentery: Small intestine, blood vessels
- Mesocolon: anchors large intestines
provides a route for blood vessels
Peritoneum
- Parietal peritoneum: Lines abdominal cavity
- Visceral peritoneum: Lining the organs. Only lines the anterior side of organs that are posterior. Like the kidneys
Submucosa Plexus
Submucosa
Myenteric Plexus
Muscularis externa
Salivary Amylase
Chemical digestion
Starts in the mouth for carbs
Teeth
32 adult teeth 20 deciduous (baby) teeth - 2 incisors - 1 canine - 2 premolars (only adults) - 3 molars
Not bones, made of inorganic salts
Enzymes of digestion
Salivary Amylase
Lingual Lipase
Lysozyme (pathogen’s wall)
Part of pharynx where food passes down
Oropharynx stratifies squamous
Pharyngeal constrictors
constrict pharynx to prevent chocking by continuing to move bolus
Esophagus
Lower esophageal sphincter: Not a true sphincter
esophagus opens as food bolus passes through
Stomach
Muscular sac that stores food Circular and longitudinal muscles a thirds layer: Oblique layer Mechanically breaks up food particles Absorption of lips soluble drugs
Chyme
Produced in the stomach.
Pasty soupy mixture of semi-digested food
Oblique layer
Third layer in the stomach
Allows the stomach to really mix the food.
Rugue
Ridges in the stomach
Mucosa
Simple columnar epithelium
Gastric Pits
Depressions in mucosa
- Cardiac, pyloric and gastric glands
- Produce gastric juice
Mucous cell
-Secret mucous lines entire stomach for protection against gastric juice
At top of the pit
Regenerative (stem) cell
Base of the pit
Regenerate and replace other cells
Pariental cells
-Secret Hydrochloric acid with the help of CAH - Also secret intrinsic factor Vit B12 Important to be able to absorb B12 - Ghrelin the hunger hormone
Chief cells
- Secrete enzymes
Pepsinogen and lipase
proteins and lipids digestion through their enzymes
Enteroendocrine cells
Lower end of pit
Secrete hormone and paracrine messengers that regulate digestion
Functions of HCl
Activates pepsin and lipase
Helps liquify things to form chyme
Iron II to Iron III which is used for hemoglobin synthesis
Destroys many pathogens
Protection against HCl in stomach
Mucos
Tight junctions
Cell replacement
Regulatory phases of the gastric system
Cephalic
Gastric
Intestinal
Cephalic regulatory phase
Sensory info preps GI tract
-Stomach responds to sensory and mental info
smelling the food, seeing the food
Gastric regulatory phase
Food gets tot he stomach stretching it
The stomach produces secretions to stimulate gastric activity:
Histamine, Gastrin, Ach
Chyme is produced
Gastrin
Produces positive feedback making the stomach produce more secretions
Intestinal gastric phase
Small intestine.
as chyme moves into the duodenum it stimulates gall bladder and pancreas to secrete their enzymes and chemicals to complete digestion.
Secretion os secretin and cholecystokinin
Secretin
Hormone that stimulates gall bladder and pancreas to secrete their secretions.
In duodenum
CCK
Cholecystokinin.
It slows down the digestive system to have enough time to absorb all nutrients.
suppress motility
Small intestine
digestion and absorption completed
Duodenum
Shortest region
Pancreatic and gall bladder enzymes
Most of the digestive process happens here
Jejunum
Highly vascularized
Absorption
villi
liver-hepatic PV- VC
Ileum
Last segment
absorption
Ileocecal valve
Ileocecal valve
One way valve in the cecum
Between ileocecal and cecum
Intestinal Motility in small intestine
Segmentation
Peristalsis
Segmentation
Circular layer
Aids absorption
chunks of stuff
Peristalsis
Longitudinal layer
Moves the material
Large Intestine
Starts at the cecum Ascending colon Transverse Descending Sigmoid
Hepatic flexure
Where ascending colon turns under the liver giving rise to transverse colon
Splenic Flexure
Where transverse colon bends at the spleen site giving rise to descending colon
Sigmoid Colon
S-shape to make way to the medial side ending at rectum
Muscularis externa (longitudinal) of the colon
Does not surround entire structure
There are 3 small bands around colon
Taenia coli
3 bands in the colon
Little longitudinal strips of the muscularis externa
Produce segments names haustra
Haustra
Formed by the taenia coli
Where compaction happens to get feces ready to be dumped out
Recto valve
In the rectum
Allows the removal of gas without defecating
Internal anal sphincter
Smooth muscle
Involuntary
Relaxes so feces can move into anal canal
External anal sphincter
Skeletal muscle
Voluntary
We learn to control this one
As we get older we lose control of this one.
Liver
4 lobes
right/left/quadrate/caudate
produces and secretes bile
Hepatocytes
Liver cells in the lobules
discontinues capillaries surrounding hepatocytes
Gall bladder
Stores and concentrates bile
Releases bile once we consume a fatty meal into the duodenum
Bile
Not an enzyme
An emulsifying agent
to increase surface are of the lipids by separating them into smaller globules
Contains cholesterol
Secretin
Stimulates gall bladder to release bile
Common bile duct
From gall bladder to duodenum to release the bile into it.
Pancreas
Endocrine and exocrine organ.
As an endocrine it secretes Insulin, glucagon
As an exocrine secretes chemicals and enzymes to complete digestion
Sodium Carbonate NaCO3
Released by the pancreas into the duodenum to neutralize chime. This allows the other enzymes to work properly
Zymogens of pancreas
Trypsin, chymotrypsin, procarboxipeptin
Enzymes of pancreas
Lipase, amylase, ribonuclease, deoxyribonuclease
