Digestive system - Part 1 Flashcards by Daniel Picard

The organs of the digestive system are divided into two groups. These are?

Alimentary canal (GI tract/digestive tract)

Accessory digestive organs

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What are the accessory digestive organs?

Teeth and tongue.

Salivary glands, gallbladder, liver, pancreas

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What are the different digestive processes?

Ingestion
Propulsion
Mechanical digestion
Chemical digestion
Absorption
Defecation

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What is ingestion?

Taking of food into the mouth

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What is propulsion?

Movement of food
Voluntary - swallowing
Involuntary - peristalsis - move food down the esophagus and SI

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What is mechanical digestion?

Mechanical breakdown of food, preparation for chemical digestion.
Chewing, churning of stomach, segmentation

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What is chemical digestion?

Where does it occur?

Chemical breakdown of complex molecules to simple components via enzymes secreted by digestive glands.

Mouth, stomach, pancreas, SI

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What is absorption?

Transport of digested nutrients from GI tract into the blood/lymph

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What is defecation?

Elimination of indigestible substances as feces

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Describe peristalsis.

Major means of propulsion
Adjacent segments of the alimentary canal relax and contract
Involuntary
Controlled by smooth muscle

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Describe segmentation.

Rhythmic local contractions of the intestine.
Mechanically breaks down food and mixes it with digestive juices.
(only in SI)
Gives maximum contact with digestive juices (chemical breakdown)

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What are the four layers of the alimentary canal?

Mucosa
Submucosa
Muscularis externa
Serosa

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What is the innermost layer of the alimentary canal wall?

What are the rest, in order?

Mucosa
Submucosa
Muscularis externa
Serosa

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What does the mucosa consist of?

Epithelium - non-keratinized stratified squamous epithelium
- simple columnar epithelium

Lamina Propia - areolar CT
Muscularis mucosae

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What does the submucosa contain?

What tissue type does it have?

Contains blood and lymphatic vessels, and nerve fibres

Moderately dense areolar CT containing elastic fibres

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The GI tract is a ______ membrane. Why?

Mucous

Open to the outside

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Why can the mucosal layer be two different tissue types?

In the mouth, esophagus, anus and rectum - will have non-keratinized stratified squamous epithelium - protect against abrasion
Simple columnar epithelium for the rest - more absorptive role and secretion of mucus

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What is the CT tissue layer under the mucous membrane?

Lamina propria - areolar CT

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What does the muscularis mucosa do?

Small layer of muscle.

If tiny fluid particles get lodged, can twitch to dislodge food lodged in the epithelium.

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Which parts of the alimentary canal have skeletal muscle? Which have smooth?

Mouth, pharynx, majority of esophagys, external anal sphincter
The rest is smooth muscle in one of two layers.

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What are the two layers of smooth muscle in the muscularis externa?

Circular muscularis
- inner layer - squeezes gut tube
Longitudinal muscularis
- outer layer, shortens gut tube

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Describe the serosa.

Outermost layer
Visceral peritoneum
Mesothelium and areolar CT.

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What is malt?

Immune cells - part of areolar CT

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Smooth muscle:
Primarily found in walls of _______.
Fibres ________.
Have ___ ______-located nucleus.
Grouped into sheets:
- Longitudinal layer - ________ to long axis of organ
- circular layer - deeper layer, fibres run around the ________ of organ

Viscera
elongated
one centrally-located
Parallel
circumference

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Describe contractions in smooth muscle.

Delayed contractions, takes a while to contract. | Prolonged contraction, can hold contractions for a while - doesn't fatigue as quickly

What is the peritoneum? What is the visceral peritoneum? What is the parietal peritoneum? What is the peritoneal cavity?

Serous membranes of the abdominal cavity. Visceral peritoneum - surrounds digestive organs Parietal peritoneum - likes the abdominal body wall Peritoneal cavity - a slit-like potential space

What is a mesentery?

Double layer of peritoneum. Holds organs in place Sites of fat storage. Provides a route for circulatory vessels and nerves.

What is the falciform ligament?

Attach liver and diaphragm to anterior abdominal wall.

What are retroperitoneal organs?

Behind the peritoneum | Major organ is the kidneys

Kidney - affixed to _____ abdominal wall - ____ and ____ for protection

posterior | CT, fat

Describe the mouth/oral cavity mucosal layer.

- Non-keratinized stratififed squamous epithelium - Lamina propria - Heals very quickly due to multiple layers and capacity to regenerate

Tongue: - Interlacing ______ of _____ muscle covered with _______ membrane - ______ food and _______ it - Tongue bounces food off the ______ - Helps form some _______

fascicles, skeletal, mucous grips, repositions palate consonants

What is the labial frenulum?

Connects lips to gums

What is the palate?

Forms the roof of the mouth

What is the lingual frenulum?

Secures tongue to floor of mouth

What is done for tongue tied babies?

Lingual frenulum too far forward, sometimes clip it back a bit

What are the pharynx cavities pertinent to digestion?

Oropharynx and laryngopharynx.

What are the oropharynx and lanryngopharynx layers?

Lined with stratified squamous epithelium, non-keratinized

How is the bolus propeled to the esophagus from the pharynx?

Muscular contractions help propel the bolus into the esophagus

Epithelium: - Tissue here is what? - When empty, the mucosa and submucosa are in what arrangement? - What lubricates the bolus? - What are the changes in the muscularis externa? - Does the esophagus have a serosa layer?

Non-keratinized stratified squamous epithelium When empty, mucosa and submucosa are in longitudinal folds Mucous glands secrete lubricating mucous Skeletal muscle for first third, transitions to smooth muscle for last third Not called serosa because the esophagus is not suspended within the peritoneal cavity, called the adventitia

The esophagus is a _________ muscular tube. What does the esophagus expand against? How does the bolus get lubricated?

collapsible trachealis muscle Bolus pushes against glands to secrete and coat it, ease passage in esophagus

What is the cardiac sphincter?

Closes lumen to prevent stomach acid from entering the esophagus Also called the lower esophageal sphincter.

Acid reflux is an issue with what?

Cardiac sphincter, lets acid splash up into the esophagus.

What are the two phases of swallowing?

Voluntary phase | Involuntary phase

Describe the voluntary phase of swallowing.

Tongue pushes food to back of oral cavity

Describe the involuntary phase of swallowing.

Pharyngeal stage Breathing stops and airways are closed. Soft palate and uvula are lifted to close off nasopharynx, Epiglottis bent to cover larynx

``` Stomach: - Site where food is churned into ______ Secretion of ______ begins digestion. - functions under ______ conditions Some substances are absorbed directly through the stomach. These are? ```

chyme pepsin acidic water, electrolytes, aspirin, alcohol

What are the folds in the stomach called? What do they do?

Rugae | Increase surface area and allow the stomach to accomodate more food

What is one difference between the stomach and other parts of the GI tract?

Stomach has three muscular layers - also have oblique layer, innermost -- takes stomach and jacknifes it to force food through pyloric sphincter into duodenum

What is the epithelium of the stomach? What does this epithelium secrete? What is the mucosa dotted with?

Simple columnar epithelium - secretes bicarbonate-buffered mucus Mucosa dotted with gastric pits with deeper gastric glands

Gastric pits contain what? | What do each do?

Mucous neck cells - secrete a special mucus Parietal cells - secrete HCL and gastric intrinsic factor Chief cells - secretes pepsinogen

Why buffered mucus?

Neutralizes acid. Protects stomach lining.

What causes stomach growling?

Gas and air bubbles get produced by the stomach during digestion. When chyme is in the system don't hear the bubbles, when there is no chyme, hear them.

What is the longest portion of the alimentary canal? | What is the site of the most enzymatic digestion?

What are the three subdivisions of the SI?

Duodenum, jejunum, ileum

Duodenum: | - Receives digestive enzymes from the ______ and bile from the ______ and ________.

pancreas | liver, gallbladder

Within the duodenum, the _____ is attached. | Gallbladder stores _______, liver produces it.

pancreas | bile

What are the modifications for absorption?

Circular folds Villi Microvilli Length

What are circular folds?

Transverse ridges of mucosa and submucosa

What are villi?

Finger-like extension of the mucosa | Covered with simple columnar epithelium made up of absorptive cells

What are microvilli?

Further increases SA for absorption

How does length increase absorption?

maximize time for chyme to spiral through | maximizes contact with digestive enzymes