Flashcards in A&P Chapter 24 Digestive System Deck (48):
What are the functions of the Digestive System?
2. Mechanical Digestion
3. Chemical Digestion
What are the two functional groups of the Digestive System?
1. 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.
2. 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.
What gland does Mumps affect?
The Parotid Salivary Gland
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.
Submucosa: Dense Irregular CT
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.
Mucosa: Simple Columnar Epithelia
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.
What type of epithelia lines the small intestine?
Simple Columnar Cilated
Describe the Jejunum:
~2.5 Meters Long and is specialized for absorption.
Describe the Ileum:
~3.5 Meters long and is specialized for absorption.
Where does the stuff that gets absorbed in the small intestine go?
They travel THROUGH the cells of the epithelia and pass into the Lamina Propria where blood and lymphatic capillaries move it to the liver and other parts of the body.
How does the small intestines structure promote absorption through increased surface area?
1. All the layers of the Mucosa are thrown into folds called Plicae Circulares.
2. The Epilethia and Lamina Propria form finger like projections called Villi.
3. The Plasma membranes of the epithelia cells form finger like projections called Microvilli.
What kind of junctions do the epithelia cells of the stomach have? Why do they have this?
Tight junctions that PREVENT ANYTHING from passing between the cells. They have these so that EVERYTHING must pass through the cells. After everything that gets absorbed passed THROUGH the cells it gets absorbed in the vasculature in the Lamina Propria.
What layer of the small intestine has the largest amount of immune cells/tissue?
The Lamina Propria, has large numbers of macrophages, lymphocytes and lymphatic nodules where those cells are multiplying rapidly.
What is the connection between the Small Intestine and Large Intestine called?
The Ileocecal Junction
Describe the Large Intestine:
Total length of ~2 meters. ~5-8cm in diameter. The large intestine primarily absorbs water and electrolytes forming feces from the undigested materials for elimination.
How long does it take for material to pass through the small intestines?
How long does it take for material to pass through the large intestine?
Trace the portions of the Large Intestine from the Ileocecal Junction to the Rectum.
Appendix, The Cecum (the pouch), Ascending Colon, The Right Colic Flexure, The Transverse Colon, The Left Colic Flexure, Descending Colon, The Sigmoid Flexure, and the Sigmoid Colon. It's followed by the Rectum and Anus.
What is the part of the Large Intestine that can be removed as an adult?
What are the Abdominal Accessory Organs to the Digestive System?
The Liver, Gall Bladder, Pancreas and associated ducts.
Describe the Liver
The largest and most superior organ in the abdominal cavity. Immediately inferior to the diaphragm. Has a mass of ~1.5kilograms.
The liver has four lobes, the Right, Left, Caudate and Quadrate lobes. These lobes can function independently.
The liver has a double blood supply from the Hepatic Artery and the Hepatic Portal Vein (which feeds blood from comes from the stomach, intestines, pancreas and spleen)
All of the vessels entering or exiting the Liver travel through the PORTA HEPATIS.
What are the DIGESTIVE functions of the liver?
It regulates metabolism.
Stores excess carbohydrates, proteins and lipids.
Secretes Bile which is stored in the Gall Bladder.
Describe Bile and it's route from the Liver to the Duodenum.
Made in the liver, Bile is produced from cholesterol and is stored in the gall bladder. It gets to the gall bladder via the CYSTIC DUCT and is transported to the Duodenum through the COMMON BILE DUCT.
Bile Emulsifies Fats.
What is the PORTA HEPATIS?
The area of the Liver where all vessels/nerves pass in and out of.
Describe the Pancreas
It is inferior and posterior to the stomach. It fits into the concavity of the Duodenum. It is both endocrine (1% Pancreatic Islets) and exocrine (98-99%)
It produces digestive enzymes and delivers them to the Duodenum of the Small Intestine through the PANCREATIC DUCT.
What are the different Digestive Enzymes the Pancreas produces? What does each do?
Amylases: Breaks Starch & Glycogen into Monosaccharides/Disaccharides.
Proteases: Breaks proteins into Amino Acids.
Lipases: Acts to break diglycerides and triglycerides into Fatty Acids and Glycerol.
Nucleases: Breaks Nucleic Acids into Nucleotides
What is the component of plant cell walls that the Digestive system lacks the enzyme to break down?
What is the double serous membrane that lines the abdominal cavity?
Describe the Peritoneum
It is a Double Serous Membrane with a Visceral layer which surrounds and is firmly attached to abdominal organs. The Parietal layer is attached to the inner surface of the body wall. The inside of the membrane is the Peritoneal Cavity.
What connects INTRAPERITONEAL organs to the body wall?
Sheets of Connective Tissue called Mesentery.
If an organ in the abdomen has a MESENTERY connecting it to the body wall what is it defined as? What if it doesn't have a Mesentery?
If the organ is connected to the body wall with a Mesentery its INTRAPERITONEAL, if its not its RETROPERITONEAL.
What organs or parts of organs are INTRAPERITONEAL?
Cecum and Appendix
What organs or parts of organs are RETROPERITONEAL?
What is INTESTINAL MOTILITY? Why is it important?
It moves liquid distally by the act called PERISTALSIS.
It mixes the CHYME from the stomach with Intestinal enzymes, pancreatic enzymes and bile from the liver.
It also increases the contact of liquid within the intestinal mucosa for absorption.
Peristalsis changes speed based on the time needed for absorption.