The Digestive System Flashcards
Digestive system
Digestive tract
GI tract
Accessory organs
Digestive tract
Oral cavity > pharynx > esophagus > stomach > small intestine > large intestine > anus
Accessory structures
Teeth, tongue, glandular organs, salivary glands, liver, pancreas and gallbladder
Ingestion
Takes place when food enters the oral cavity
Mechanical digestion and propulsion
Involves crushing and shearing of food and then propelling the food along the digestive tract
Chemical digestion
Refers to the chemical breakdown of food into small organic and inorganic molecules suitable for absorption by the digestive epithelium
Secretion
Release of water, acids, enzymes, buggers and salts by the epithelium of the digestive tract, glandular organs and the gallbladder
Absorption
Movement of organic molecules, electrolytes, vitamins, minerals, and water across the digestive epithelium
Defecation
Elimination of wastes from the body
Pharynx
Muscular propulsion of materials into the esophagus
Esophagys
Transport of materials to the stomach
Stomach
Chemical digestion of materials by acid and enzymes; mechanical digestion through muscular contractions
Small intestine
Enzymatic digestion and absorption of water, organic substrates, vitamins and ions
Large intestine
Dehydration and compaction of indigestible materials in preparation for elimination
Salivary glands
Secretion of lubricating fluid containing enzymes that break down carbohydrates
Liver
Secretion of bile, storage of nutrients, many other vital functions
Gallbladder
Storage and concentration of bile
Pancreas
Exocrine cells secrete buffers and digestive enzymes; endocrine cells secrete hormones
Peritoneum
Serosa/visceral peritoneum
Pariteal peritoneum
How can the visceral and parietal surfaces slide without friction?
Peritoneal fluid
Ascites
Abdominal swelling caused by the buildup of fluid in the peritoneal cavity
Mesentries
Double sheets of peritoneal membrane that connect with the parietal peritoneum with the visceral peritoneum
Lesser omentum
Stabilises the position of the stomach and provides an access route for blood vessels and other structures entering or leaving the liver
Falciform ligament
Helps stabilise the position of the liver relative to the diaphragm and abdominal wall
Greater omentum
Pouch formed from the enlarged dorsal mesentery
Contains adipose tissue that conform to the shape of the surrounding organs
Mesentery proper
Suspends the small intestine
Thick mesenterial sheet
Peritonitis
Inflammation of the peritoneum
Mesocolon
Mesentery associated with a portion of the large intestine
Layers of the digestive tract
- Mucosa
- Submucosa
- Muscular layer
- Serosa
Layers of the mucosa
- Mucosal epithelium: epithelial cells that differ depending on the place (stratified squamous where there’s mechanical stress, etc.)
- Laminar propria: areolar tissue
- Muscularis mucosae: smooth muscle and elastic fibres
Submucosa
- Dense irregular connective tissue
- Connects mucosa and muscular layer
- Submucosal neural plexus in the margin
Muscular layer
- Smooth muscle cells
- Coordinated by enteric nervous system
- Contains myenteric plexus
Serosa
Covers the muscular layer along portions of the digestive tract enclosed by peritoneal cavity
Adventitia
Fibrous sheath in areas lacking serosa
Peristalsis
Circular muscles contract behind the bolus while circular muscles ahead of the bolus relax
Longitudinal muscles ahead of the bolus then contract, shortening adjacent segments
A wave of contraction in the circular muscles then forces the bolus forward
Segmentation
Cycles of contraction that churn and fragment the bolus, mixing the contents with intestinal secretions
Local factors regulating digestive activities
- Primary stimulus
- Coordinate the responses to changes in the pH of the contents of the lumen, physical distortions of the wall, or the presence of chemicals
Neural control mechanisms
Myenteric reflexes (chemoreceptors, stretch receptors) Long reflexes (higher level control)
Hormonal control mechanisms
Peptides produced by enteroendocrine cells (endocrine cells in the epithelium of the digestive tract)
Functions of the oral cavity
- Sensory analysis
- Mechanical digestion
- Lubrication
- Chemical digestion
What lines the oral cavity?
Oral mucosa
Stratified squamous epithelium
What supports the mucosae of the cheeks?
Buccal fat pads and buccinator muscles
Oral vestibule
Space between the cheeks and the teeth
Gingivae
Gums
Ridges of oral mucosa surrounding the base of each tooth on the alveolar processes of the maxillae and the alveolar part of the mandible
Uvula
Dandling process that helps prevent food from entering the pharynx too soon
Palatoglossal arch
Between the soft palate and the base of the tongue
Fauces
Space between the oral cavity and the pharynx bounded by the soft palate and the base of the tongue
Palatopharyngeal arch
Extend from the soft palate to the pharyngeal wall
Functions of the tongue
- Mechanical digestion
- Manipulation
- Sensory analysis
- Secretion of mucins and lingual lipase
Lingual lipase
Digests lipids
Extrinsic tongue muscles
Large
Perform all gross movements
Intrinsic tongue muscles
Small
Change the shape of the tongue, precise movements
How does dentin differ from bone?
It doesn’t contain cells
Pulp cavity
Receives blood vessels and nerves through root canal
Apical foramen
Opening where blood vessels and nerves enter the root canal
What covers the dentin of the root?
A layer of cement
Gingival sulcus
A shallow groove surrounding the neck of each tooth
What covers the dentin of the crown?
A layer of enamel
Occlusal surface
Biting surface that grinds food against the opposing tooth surface
Formed by enamel
Cusps
Elevations or projections of the occlusal surface
Types of teeth
- Incisor teeth
- Canine teeth
- Premolar teeth
- Molar teeth
Incisor
Front of mouth
Blade shaped
Canine
Conical with a pointed cusp
Lie under the eye
Premolar
Have flattened crowns with two prominent cusps
Molar
Very large flattened crowns with 4-5 prominent rounded cusps
Decidious teeth
- Baby teeth
- Most children have 20
3 pairs of salivary glands
- Parotid glands
- Sublingual glands
- Submandibular glands
Parotid glands
- Contain salivary amylase which breaks down starches
- Drained by parotid ducts
Sublingual glands
- Covered by mucous membrane of the floor of the mouth
- Produce mucous
Submandibular glands
- Secrete a mixture of buffers, mucins and salivary amylase
What gives saliva its lubricating action?
Mucins
Functions of saliva
- Lubricating the mouth
- Lubricating food in the mouth
- Dissolving chemicals
- Beginning digestion
What controls salivary secretions?
Autonomic nervous system
Each salivary gland has sympathetic and parasympathetic innervation
Superior and inferior salivatory nucleus
Where parasympathetic efferents originate
In the medulla oblongata
Pharynx
Throat
Serves as a common passageway for solid food, liquid, and air
Esophagus
Actively moves ingested materials down towards the stomach
Esophageal hiatus
Opening in the diaphragm where the esophagus enters the abdominopelvic cavity
Wall of the esophagus
Mucosa, submucosa and muscular layer
Function of folds in the esophagus
They allow for expansion during the passage of a large bolus
Where are esophageal glands?
Scattered among the submucosa
They produce mucus that reduces friction between bolus and esophageal lining
What innervates the esophagus?
Parasympathetic and sympathetic fibres from the esophageal plexus
Degluition
Swallowing
Phases:
- Buccal
- Pharyngeal
- Esophageal
- Bolus enters stomach