A&P Chapter 24 Digestive System Flashcards
What are the functions of the Digestive System?
- Ingestion
- Mechanical Digestion
- Chemical Digestion
- Propulsion
- Absorption
- Defecation
What are the two functional groups of the Digestive System?
- The Alimentary Canal or GI Tract: Organs which ingest, propel, digest, absorb and eliminate. This includes the oral cavity, pharynx, esophagus, stomach, small/large intestines and anus.
- The Accessory Digestive Organs: These assist with digestion. The teeth, tongue, salivary organs, liver, gall bladder, and pancreas.
What enzyme is secreted by salivary glands that begins chemical digestion as food is in the oral cavity?
Amylase, it is an enzyme that breaks down carbohydrates.
What is the landmark that divides the neck from the thoracic cavity?
The 1st rib, everything above is neck/head and everything below to the diaphragm is the thoracic cavity.
Describe The Oral Cavity
It includes the 32 teeth and tongue. It opens posteriorly into the pharynx which opens inferiorly to the esophagus. Contains the ducts for the paired Salivary glands.
What are the pair salivary glands?
Parotid: The largest who’s ducts empties between the cheek and second molars.
Submandibular:
Sublingual:
What gland does Mumps affect?
The Parotid Salivary Gland
Describe Saliva:
97-99% Water, it contains solutes such as Ions, Antibodies, Lysozyme, Amylase and Mucous.
It acts to lubricate the oral cavity, to clean the mouth/teeth. It contains Lysozyme as a first line Immune defense, and it begins carbohydrate digestion with Amylase.
Is swallowing a somatic or visceral motor function?
Both, it begins as a somatic or voluntary motor function but once food passes into the esophagus it becomes a visceral or involuntary motor function.
Describe the action of swallowing.
Teeth and tongue chew/mash food into a bolus which passes from the oral cavity into the oropharynx. The uvula of the soft palate presses up against the posterior wall of the pharynx preventing food from going up into the nasal cavity while the epiglottis extends downward covering the opening to the larynx. This creates a single path for food to travel into the esophagus.
Describe the Layers of the Alimentary Canal from Inner to Outer
Mucosa: Consists of an Epithelium (And Always a Basement Membrane), A Lamina Propria (Loose Areolar Connective tissue) and a Muscularis mucosa (A thin sheet of smooth muscle).
Submucosa: Dense irregular connective tissue containing large numbers of glands, nerves and blood vessels.
Muscularis Externa: Thick layer of muscle (sometimes skeletal others smooth) responsible for peristalsis/movement of food/digesting matter.
Serosa or Adventitia: A layer of connective tissue which may be lined on the outside with a simple squamous epithelium (Serosa) or without (Adventita)
What is the job of the Muscularis mucosa?
To change the shape of the mucosa, NOT to move food along the pathway.
Describe the Esophagus
It propels food from the pharynx to the stomach. It is posterior to the trachea and heart. The esophagus passes from the thorax to the abdomen through (behind) the diaphragm and enters the stomach just left of midline.
It has a Mucosa with a NON KERITINIZED STRATIFIED SQUAMOUS epithelial layer, a thin Lamina Propria and a very thin muscularis mucosa.
The Submucosa is a thick layer of dense irregular connective tissue.
The Muscularis Externa transitions from skeletal muscle in the top 1/3rd to smooth muscle in the lower 1/3rd.
It has an Adventitia made of connective tissues.
Describe the Stomach
Is a highly distensible organs in the left upper quadrant of the abdomen. The stomach is in the peritoneal cavity and delivers CHYME to the Duodenum of the small intestine.
The stomach is broken into different regions, the cardiac region is closest to esophagus. The fundus is the superior region, the body is the largest region and the pyloric region is on the inferior portion.
The stomach secrets Pepsin to digest proteins.
The muscularis mucosa layer forms RUGAE which are folds inside the stomach.
The stomach is lined by a Serosa.
What are the folds of the stomach lumen? What makes them?
They are called RUGAE and they are created by the MUSCULARIS MUCOSA layer.
What are the three layers of muscle that form the MUSCULARIS EXTERNA of the Stomach?
Oblique (Inner) Layer of Muscle
Circular (Middle) Layer of Muscle
Longitudinal (Outer) Layer of Muscle
What are the layers of the stomach Inner to Outer? Be detailed including epithelia type and names for muscles.
Mucosa: Lamina Propria Muscularis Mucosa Submucosa: Dense Irregular CT Muscularis Externa: Oblique Layer Circular Layer Longitudinal Layer
Describe the Small Intestine:
Total length of 6-7 meters. Diameter of 2.5-3cm.
Connects to the stomach with the Duodenum, proceeds to the Jejunum and ends with the Ileum.
Layers Mucosa: Simple Columnar Epithelia Lamina Propria Muscularis Mucosa Submucosa: Muscularis Externa: Serosa or Adventita:
Describe the Duodenum
The shorest section of the small intestine. It’s 25cm long and receives secretions from the liver (bile) and the pancreas (digestive enzymes).
It secrets Mucous, Digestive enzymes and Bicarbonate.