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24 Cards in this Set

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General Function of Digestive Tract
Function: digestion, barrier (prevent pathogens from entering with the food)

Components:
- oral cavity, teeth, tongue
- liver, gallbladder
- large intestine, small intestine
- salivary glands
- pharynx, esophagus
- stomach, pancreas
Generalized Digestive Tract: Four Main Layers (digestion and hormone production)
1. Mucosa- epithelial lining; lamina propria (loose CT); muscularis musosae (thin muscular layer)

2. Submucosa- consisting of dense irregular CT. Submucosal nerve plexus (the function of the submucosa is for support)

3. Muscularis- the main muscle function; two layers (circular and longitudinal) of smooth muscle; myenteri nerve plexus

4. Serosa- furthest outside; a serous membrane consisting of a simple squamous epithelium, the mesothelium, and a small amount of underlying CT.
Oral Cavity- Two Subdivisions
* Two Subdivisions:
1. Vestibule- space between the lips, cheeks and teeth
2. Cavity- lies behind the teeth and is bounded by the hard and soft palates superiorly, the tongue and the floor of the mouth inferiorly, and the entrance to the oropharynx posteriorly.
Components of the Oral Cavity
- lips
- cheeks
- gums
- tongue
- palate
- teeth
Oral Cavity- three types of mucosa
1. Masticatory mucosa- found on the gingiva (gums) and hard palate. It is keratinized and, in some places, a parakeratinized stratified squamous epithelium (the nuclei are still there and highly condensed).

2. Lining Mucosa- found on the lips, cheeks, alveolar mucosal surface, floor of the mouth, inferior surfaces of the tongue, and soft palate. Non-keratinized, prone to movement (it has fewer and shorter papillae so that it can adjust to the movement of the underlying muscles)

3. Specialized Mucosa- associated with the sensation of taste and is restricted to the dorsal surface of the tongue. It contains papillae and taste buds responsible for generating the chemical sensation of taste.
Lips- components
* Cutaneous- thin, keratinized, hair

* Red- thick, keratinized, papillae

* Oral Mucosa- thick, parakeratinized (nuclei associated)
Cheek and Gum
* Cheeks:
- nonkeratinized
- dense lamina propria and submucosa

* Gums:
- keratinized
- lamina propria bound to periosteum and periodontal
- lack submucosa or glands
Palatine
* Hard Palate:
- Masticatory mucosa
- Submucosa along midline

* Soft Palate:
- lining mucosa
- nonkeratinized
- skeletal muscle associated- allows some voluntary control
Salivary Glands
* Parotid glands (by ears):
- temporal region
- duct at 2nd moral
- 25% of saliva comes from here

* Submandibular gland (back part of mouth):
- submandibular triangle
- duct at lingual frenulum
- 70% of saliva comes from here

* Sublingual:
- Sublingual folds
- numerous ducts
- very little saliva comes from here
Tongue
* Muscle Mass:
- striated
- 3 layers, bundles (the muscle is arranged in bundles that generally run in three planes)
- connected lamina propria

* Mucous Membrane:
- smooth underside
- irregular dorsal surface:
papillae
lymphoid aggregates
Four Types of Papillae
1. Filiform- across surface of tongue, increase friction, curve shaped, point backward. smallest and most numerous.

2. Foliate- aren't as well developed in humans. Tastebuds located on top. occur on the lateral edge of the tongue.

3. Fungiform- mushroom shaped; near tip of tongue. tend to be more numerous near the tip of the tongue, taste buds are present here.

4. Circumvallate- huge dome-shaped ones; form distinct dots in a V-shape. Human tongue has 8-12 of these.
Taste Buds
- they form a barrel-shaped structure with a pore opening
- four tastes (sweet, sour, salty, bitter)
* Cell Types:
- Taste
- Supportive
- Basal
* Sensation
* Familial dysautonomia

* Umami- represents the taste of certain amino acids (MSG)
Teeth
* Crown (the exposed area above the gum line):
- Enamel- acellular; 95% mineralized tissue, hardest substance in your body

*Root:
- Alveoli (the socket where the root of the tooth fits into)
- Cementum (thin layer of bone-like calcified tissue covering the dentin of the root of the teeth)

*Cervix (neck)

*Dentin- also acellular; a calcified material that forms most of the tooth substance. It lies deep to the enamel and cementum.

* Pulp cavity- space within a tooth that is occupied by dental pulp (loose CT that is vascularized and nerves present)

* Periodontal ligament (fibrous CT joining the tooth to its surrounding bone)

*Gingiva (commonly called the gums)- soft epithelium (the tissue in between teeth)
Contents of the pulp cavity
- Central Chamber
- Apical Foramen(where the blood vessels and nerves enter the pulp cavity at the tip of the root)
Esophagus Layers
a tube for food transporting

Four Layers:
- mucosa (protection, absorption, secretion)
- submucosa (consists of a dense irregular CT layer containing blood and lymphatic vessels, a nerve plexus, and occasional glands)
- muscularis externa (two layers- circular and longitudinal)
- serosa (the outermost layer consisting of mesothelium)
Esophagus
- upper portion is striated, middle is a mix, and lower is smooth muscle

*Mucosa:
- nonkeratinized
- esophageal cardiac gland (secretes a mucus; located in lamina propria)

* Submucosa:
- esophageal glands (secrete)

*Muscularis:
- inner = circular
- outer = longitudinal

*Serosa (reduced in upper portion and more prominent in lower portion)
Esophagus- Stomach Junction
- an abrupt switch occurs
Stomach
- a mixed exocrine (releases into ducts)- endocrine (releases it on a surface) organ
- function: digestion

*Digestion:
- carbohydrates (amylase)
- proteins (pepsin)
- triglyceride (lipases)
- form Chyme (a mush of everything in the stomach)

* Rugae- lateral folds in walls of stomach- allow it to expand
Four Regions of the Stomach
- Cardia
- Fundus
- Body
- Pylorus
Stomach Mucosa
- Epithelium: simple columnar (secrete alkaline mucus to protect it from digestive enzymes); gastric pits (extend down into the lamina propria)
- Lamina Propria (loose CT): muscularis mucosae (separates lamina propria from underlying submucosa)
Fundus (body)
- fundus and body are histologically the same

*Gastric Glands:
- Parietal Cells
- Chief Cells
- Mucous Neck
- enteroendocrine- hormone producing cells

Neck of Fundus: parietal cells (HCl); Mucous

Base: chief cells (make pepsinogen); enteroendocrine cells

A collection of stem cells is also present that makes more of these cells
Parietal Cells
take up CO2 from blood --> bicarbonate and proton made --> proton goes outside of cell and bicarbonate

K and Cl ions outside of cell

Proton and Cl make HCl
Chief Cells
- Lower region of glands= basal portion
- Pepsinogen (makes pepsin which digests proteins)
- Lipase

- granules associated with chief cells
- nuclei, Golgi present
Pylorus
- deep gastric pits (longest pits- secrete mucus and make lysozyme)

- pyloric glands

- Gastrin cells- in pyloric glands; hormone-producing glands (produce gastrin)