The Digestive System Flashcards
What are the 6 steps of digestive processing?
- Ingestion
- Mechanical Breakdown
- Propulsion
- Digestion
- Absorption
- Defecation
Describe peristalsis:
Adjacent segments of alimentary tract organs alternately contract and relax, moving the food along the tract distally.
Think squeeze then pull
Describe segmentation:
Nonadjacent segments of alimentary tract organs alternatively contract and relax, moving food forward then backward.
Think pushing and continually rubbing up against the wall
The alimentary canal is inside the body right?
While it might be “inside the body” it is technically one big tunnel that is considered to be outside the body.
Why is it important to regulate the alimentary canal?
To ensure effective breakdown and absorption.
What do the sensors located in the walls of the alimentary organs sense?
Stretch
Osmolarity
Ph
Substrates
End Products
What do the sensors in the walls of the organs cause?
- Initiate reflexes that activate or inhibit glands that secrete into the tube or into the blood
- Cause muscle contractions or cause the muscle to relax
What are the intrinsic controls of the alimentary canal?
Nerve plexuses and hormone producing cells within the tube itself that cause short reflexes.
What are long reflexes initiated by?
Initiated outside of the gut by the CNS
What line the abdominal cavity?
A serous membrane called the peritoneum
Describe the visceral layer of the abdominal cavity:
It covers most digestive organs and is continuous with the parietal layer
What is between the two layers?
The peritoneal cavity which is filled with serous fluid
What attached the transverse colon to the body wall?
Transverse mesocolon
What connects the small intestine to the body wall?
The mesentery
What is the stomach attached to?
The lesser curvature of the stomach is attached to the liver
Describe the greater omentum?
It is an apron of fat for protection that is attached to the greater curvature of the stomach where it then comes down to cover the organs before flipping up an attaching to the transverse mesocolon
Starting at the stomach, in order from deep to superficial, what are the fours layers of the alimentary canal?
- Mucosa
- Sub Mucosa
- Muscularis Externa
- Serosa
Starting at the stomach, in order from deep to superficial, what are the fours layers of the alimentary canal?
- Mucosa
- Sub Mucosa
- Muscularis Externa
- Serosa
What are the three functions of the mucosa?
- Secretes mucus, digestive enzymes, and hormones
- Absorbs nutrients
- Protects against disease
What are the three layers of the Mucosa starting at the deepest layer?
- Epithelium
- Lamina Propria
- Muscularis Mucosae
Describe the epithelial layer of the mucosa:
stratified squamous or simple columnar
Describe the Lamina Propria layer of the mucosa:
loose areolar CT, blood supple, and malt
Describe the muscularis mucosae
It determines the size of the lumen
When it is contracted it is wrinkled and when it is relaxed it is open
Describe the submucosa layer of the alimentary canal:
It is a much thicker layer of lose areolar CT than the Lamina propria and t contains blood vessels, nerves, and lymphatic vessels
Describe the muscularis externa layer of the alimentary canal:
It is comprised of smooth muscle in an outer longitudinal layer and an inner circular layer.
It also makes the sphincters
Describe the serosa layer of the alimentary canal:
It is the visceral peritoneum and the adventitia on the esophagus
What is the enteric nervous system?
It is the in house nerve supply that control motility and secretions
The On/Off Switch of the Alimentary Canal
(what are we secreting and what do we have to stop secreting
What are the two plexuses of the enteric nervous system and where are they locate
Submucosal plexus - Located in the submucosa
Myenteric Plexus - Located between the layers of the muscularis externa
What is another name for the oral cavity?
Buccal cavity
Describe the oral cavity:
Contained by the lips, cheeks, palate, tongue, and oropharynx
Comprised of stratifies squamous epithelium
Describe the lips and cheeks
Made of the skeletal muscles orbicularis oris and buccinator
Oral vestibule
What four structures comprise the mouth?
- Buccal cavity
- Lips and cheeks
- Palate
- Tongue
Describe the palate:
Made up of the hard palate and the soft palate
Describe the hard palate:
Comprised of the maxilla and palatine bones
Describe the soft palate:
Comprised of skeletal muscle, spongy tissue, and the uvula
Describe the tongue:
It is extremely strong, sensitive, and agile
Takes up most of the room in your mouth when it is closed
It is intrinsic muscles that work within the mouth and extrinsic muscles that actually do the visible movement
How can a person have no palate?
During fetal development, if the maxilla and palatine bones do not fuse properly then the person will be born without a palate.
What are the consequences of being born without a palate?
there is the risk of food or drink being aspirated into the respiratory system
What type of receptor are taste buds?
chemoreceptors
What is the rule regarding the variations in thinking something tastes good?
Everyone feels the same sensation but the individual nuanced perceptions are different.
What type of joint holds teeth in their correct position?
Gomphosis joint
What are the purpose of teeth?
Function in mastication
What are the four type of teeth?
- Incisors
- Canine
- Pre-molars
- Molars
How many deciduous teeth and how many adult teeth?
20 deciduous teeth
32 adult teeth
How are teeth generally replaced and at what age are most deciduous teeth replaced by adult teeth?
Generally replaced front to back
by age 12-13
What might explain why so many people have trouble with their wisdom teeth?
A slightly smaller jaw along with the fact that we are keeping our teeth for longer.
What is the largest gland of your mouth and overlies the masseter muscle?
Parotid gland
Which gland produces the majority of the saliva?
Submandibular gland
Describe intrinsic glands:
Produce saliva at a slow but constant rate
Describe extrinsic glands:
They produce the majority of saliva
What are the three salivary glands?
- Parotid
- Submandibular
- Sublingual
Describe the roles of the mucous and serous cells in the salivary glands:
Serous cells secrete a kind of watery component
Mucous cells secrete a thicker mucin protein that’s going to make mucous
Together they form functioning digestive saliva
What are three properties of saliva?
- Mostly water > 97%
- Hypotonic
- Slightly acidic - pH 6.75-7.0
What are 6 constituents of saliva:
- Electrolytes
- Salivary Amylase
- Lingual lipase
- IgA
- Lysozyme
- Mucin
What is the function of salivary amylase?
Works at the pH of the mouth to break down carbs immediately.
What is the function of lingual lipase?
Break down fats but not until the stomach
What is a lysozyme?
General antimicrobial enzyme in your saliva
About how much saliva do you secrete a day?
1.5 L/day
What cause the feeling of tightness in front of your ears when you consume something sour?
Your parotid glands contracting as hard as they can to get as much saliva as possible into your mouth
What two parts of the pharynx are a part of the digestive system?
- Oropharynx
- Laryngopharynx
What tissue makes up the pharynx and why?
Stratified squamous epithelium with many mucous glands in order to provide protections from swallowing
What makes up the walls of the pharynx?
Skeletal muscles
What does the pharynx lead into?
Esphagus
Describe the esophagus:
A 25 cm muscular tube that travels straight down the mediastinum and goes through the diaphragm at the esophageal line
Where does the esophagus join the stomach at?
At the cardia, lower esophageal (cardia, gastroesophageal) sphincter
What is the esophageal comprised of?
The top 1/3 if purely skeletal muscle
The bottom 1/3 is purely smooth muscle
The middle 1/3 is a mix of skeletal and smooth muscle