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The Digestive System

Terms in this set (106)

Food particles ingested, must be broken down into small enough molecules to enter body cells. This process is called
digestion
The organs involved in the breakdown and absorption of food are collectively called the
digestive system
Mouth, pharynx, esophagus, stomach, small intestine, and large intestine
Gastrointestinal (GI) Tract
Teeth, tongue, salivary glands, liver, gallbladder, and pancreas
Accessory Digestive Organs
6 Basic Functions of digestive system
1. Ingestion
2. Secretion
3. Mixing and propulsion
4. Digestion
5. Absorption
6. Defecation
4 Basic layers of the GI Tract
mucosa, submucosa, muscularis, serosa
What is mucosa in direct contact with?
the GI contents
type varies along length of GI tract,
-Protective function
-Functions in secretion and absorption
-Enteroendocrine cells- secrete hormones
Epithelium
Contains many blood and lymph vessels which help move absorbed nutrients.
-MALT tissue that helps protect against pathogens
Lamina Propria
Thin smooth muscle that creates folds to increase surface area
Muscular Mucosa
Binds the Mucosa to the Muscularis
Submucosa
Skeletal muscle in mouth, pharynx, and superior and middle parts of esophagus for swallowing.
-Smooth muscle in rest of tract.
-2 sheets: inner circular fibers & outer longitudinal fibers
-3 sheets in stomach: additional oblique fibers
Muscularis
A serous membrane that secretes a slippery watery fluid that allows the tract to glide easily against other organs.
-Adventitia superior to diaphragm
-Visceral peritoneum inferior to diaphragm
Serosa
-Largest serous membrane in body
-Parietal peritoneum lines abdominopelvic cavity
-Visceral peritoneum covers organs
-Peritoneal cavity is the space between the 2 membranes and contains serous fluid
Peritoneum
Some organs outside peritoneal cavity, but inside abdominopelvic cavity; covered only anteriorly by peritoneum (kidneys, pancreas)
Retroperitoneal
Contains large folds that weave between organs for support and contain blood, lymph vessels and nerves
Peritoneum
5 major folds of peritoneum
1. greater omentum
2. falciform ligament
3. lesser omentum
4. mesentery
5. mesocolon
-The largest peritoneal fold.
-Drapes over intestines like a fatty apron.
-Has 4 layers with a high amount of adipose tissue
-Gives rise to the "beer belly"
Greater Omentum
-Attaches liver to anterior abdominal wall.
-Liver is the only digestive organ attached to the anterior abdominal wall.
Falciform Ligament
-Suspends the stomach and duodenum from the liver.
Lesser Omentum
-Fan shaped fold of peritoneum.
-Binds the small intestines to the posterior abdominal wall.
Mesentery
-2 separate folds of peritoneum
-Binds large intestines to the posterior abdominal wall
Mesocolon
-The Brain of the gut
-Regulates GI tract
-100 million neurons that extend from esophagus to anus
Enteric nervous system
2 networks of the neural innervation of GI Tract
1.Myenteric Plexus
2.Submucosal Plexus
-controls GI tract motility (movement)
- frequency and strength of Muscularis contractions
Myenteric Plexus
Controls the secretions of the organs of the GI tract
Submucosal Plexus
-Helps regulate enteric nervous system
-Parasympathetic
-Sympathetic
-AUTONOMIC NERVOUS SYSTEM
increases secretion and motility
Parasympathetic
decreases secretion and motility
Sympathetic
Formed by muscular cheeks, hard and soft palates and tongue
Mouth- aka- Oral Cavity
The lateral walls of the mouth
Cheek (Buccinator Muscles)
-contain the orbicularis oris muscle
-Each lip attached to the gum by theLabial Frenulum
Lips (Labia)
means entrance to a canal
-space bounded by cheeks, lips, teeth, and gums.
Vestibule
-opening between oral cavity and throat
Fauces
-forms the roof of the mouth.
-Makes it possible to chew and breathe at the same time
-Hard palate - bony anterior roof
-Soft palate - muscular posterior roof
Palate
-closes off nasopharynx during swallowing.
-This prevents food and liquids from entering the nasal cavity
Uvula
The posterior border of the mouth opens into the ____________
Pharynx
Skeletal muscle, Forms the floor of the oral cavity
Tongue
-originate outside the tongue.
-hold tongue in position, and move tongue to maneuver food and for swallowing
Extrinsic muscles
-alter shape and size of tongue for speech and swallowing
Intrinsic muscles
-anchors inferior portion of tongue to the mouth floor and limits tongue movements posteriorly.
Lingual Frenulum
-secrete the enzyme Lingual Lipase which begins the digestion of triglycerides.
Lingual Glands
-tiny nipple like projections
-contain taste buds, receptors for touch, and increase friction for maneuvering food
Papillae
-Accessory digestive organs located in sockets of mandible and maxilla
Teeth
Teeth are anchored by the
periodontal ligament-Which also acts as a shock absorber during chewing.
Teeth are covered by
Gingiva (gums)
3 Major external regions of teeth
1) Crown- visible portion above gum line
2) Root- 1 to 3 embedded in the socket
3) Neck- where crown and root meet, near gum line
Teeths internal components
1- Dentin
2-Enamel
3-Pulp Cavity
4-Root Canal
-forms majority of tooth
-Calcified connective tissue that gives the tooth its basic shape and rigidity.
-Dentin in the root is covered by another bonelike substance called cementum
Dentin
Dentin in the root is covered by another bonelike substance called
cementum
-covers the dentin of the crown
- hardest substance in the body
Enamel
Space within the crown filled with Pulp
Pulp Cavity
Contains nerve, blood and lymph vessels
Pulp
-Narrow extensions of pulp cavity
-Each canal has an opening at its based called an Apical foramen
Root Canal
Through which nerve, blood and lymph vessels travel through
Apical foramen
Humans have 2 _____________ (sets of teeth)
Dentitions
-first set of teeth
-Begin to erupt at about 6 months of age.
-20 teeth in total
Deciduous
-Replace deciduous teeth
-32 teeth in total
Permanent Dentitions
4 types of adult teeth
Incisors, cuspids (canines), premolars (bicuspids), molars.
-chisel-shaped, closest to midline
-8 in total, (4 in upper set, 4 in lower set)
-Central or lateral based on position
Incisors
-Has a pointed surface called a cusp
-next to incisors
-4 in total that are used to shred and tear food
Cuspids (canines)
Incisors and Cuspids have a .....
single root
-8 in total
-Have 2 cusps and 1 root
-Used for crushing and grinding
-Premolars (bicuspids)- 1st and 2nd
-12 in total
-3rd molars are also known as wisdom teeth.
-4 cusps
-Maxillary molars have 3 roots
-Mandibular molars have 2 roots
-Crush and grind food
-Molars- 1st, 2nd and 3rd
Produce and release saliva into oral cavity through ducts
Salivary Glands
-Most saliva is secreted by 3 pairs of salivary glands
-Parotid Glands
-Submandibular Glands
-Sublingual Glands
-located near the ears, between the skin and the masseter.
Parotid Glands
In the floor of the mouth, beneath tongue
Submandibular Glands
Beneath the tongue, superior to submandibular glands
Sublingual glands
The secretion of saliva is controlled by the autonomic nervous system
Salivation
Mastication means
Chewing
-Mechanical digestion and mixes food with saliva
-Food is reduced to a soft, flexible, easily swallowed mass called abolus
Mastication
2 Enzymes of Chemical Digestion
1- Salivary amylase
2- Lingual lipase
Begins digestion of starches
Salivary amylase
Will break down dietary triglycerides (fats and oils) once it reaches acidic environment of stomach
Lingual lipase
When food is swallowed, it moves from the mouth into the __________
Pharynx (throat)
Funnel shaped tube that Extends from internal nares to Esophagus posteriorly
and Larynx anteriorly
Pharynx
Functions in respiration only
Nasopharynx
These 2 both have digestive and respiratory functions
1-Swallowed food passes from the mouth into the oropharynx and then the laryngopharynx.
2-Skeletal muscle contractions help propel food to esophagus during deglutition (Swallowing)
Oropharynx, Laryngopharynx
Degulutition
Swallowing
-Means "Eating Gullet"
-Collapsible, smooth muscle tube that connects the pharynx to the stomach for transport
Esophagus
This is 10 inches long, posterior to trachea
Esophagus
The esophagus begins at inferior end of laryngopharynx and extends thru an opening in the diaphragm called the ___________________ _______________
Esophageal Hiatus
When a portion of the stomach protrudes up through the esophageal hiatus
Hiatal Hernia
2 sphincters formed by the muscularis
1. Upper Esophageal Sphincter
2. Lower esophageal sphincter
-Regulates movement of food from pharynx into esophagus
Upper esophageal sphincter
-Regulates movement of food from esophagus to stomach, and prevents regurgitation of acidic stomach contents
Lower esophageal sphincter
What has no absorption
Esophagus
Esophageal stage (involuntary)
-Passes bolus from esophagus into stomach
-Peristalis begins-rhythmic, wavelike contractions of muscle push the blue along.
-J-shaped enlargement of GI tract
-Inferior to diaphragm, connects esophagus to duodenum
-Serves as a mixing chamber & holding reservoir.
-Digestion of starch continues
-Digestion of proteins and triglycerides begins
-The semisolid bolus is converted to a liquid
Stomach
4 Major regions of the stomach
1. Cardia
2. Fundus
3. Body
4. Pylorus
Cardia
surrounds the superior opening of the stomach
Fundus
rounded portion superior to the Cardia
Body
Large central portion of stomach
Pyloris
Region of stomach that connects to duodenum
Internal folds of mucosa that line the stomach
Rugae
Separates pylorus and duodenum
Pyloric Sphincter
Concave medial border of the stomach
Lesser Curvature
Convex lateral border of the stomach
Greater Curvature
-layer of simple columnar epithelium that lines the mucosa layer.
-Secretes mucous
Suface Mucous Cells
-columns of surface Mucous cells
-Secrete gastric juice
Gastric Glands
Several Gastic glands open into narrow channels called _____________ _________
Gastric pits
produce intrinsic factor and hydrocloric acid
Parietal Cells
secrete pepsinogen and gastric lipase
Chief Cells
secrete the hormone gastrin into the bloodstream.
Enteroendocrine cells
The Muscularis of the stomach is composed of 3 layers of smooth muscle
1-Outer Longitudinal Layer
2-Middle circular layer
3-Inner oblique layer
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