Digestive System Flashcards by Jessica Wadeson

Ingestion

Mouth only

Taking food into digestive tract

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Propulsion

Moving food though the GI tract

Gets food to the end of large intestine

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Deglutition

Swallowing (job of mouth)

Voluntary

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Peristalsis

Major means of propulsion

Alternating waves of contraction and relaxation of muscles in the organ walls

In pharynx, esophagus, small intestine, large intestine

Voluntary

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Mechanical breakdown

Job of teeth and tongue
Mastication
Segmentation

Increases SA of ingested food (physically preparing it for digestion)

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Mastication

Chewing

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Segmentation

Happens in stomach and intestines

Mixing/churning of contents

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Digestion

Chemical breakdown (altering chemical materials)
Mouth: carbs and fats
Stomach: proteins

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Absorption

Passage of digested end products from lumen of GI tract through mucosal cells –> blood or lymph

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Defecation

Job of large intestine (colon)

Removing waste produces (indigestible substances)

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Peritoneum

Outer covering (serous membrane; epithelial tissue)

Visceral (serosa): physically on organ
Parietal: on abdominopelvic wall
Layers are continuous with each other

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Mesentery

Visceral and parietal peritoneum back-to-back
Double layer
Layer of fat
Blood vessels, nerves, lymphatic vessels all pass through
Glues organs to abdominal wall (holds organs in place)

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Retroperitoneal organs

Not covered in mesentery (outside or behind)

Pancreas, duodenum, ascending + descending colon

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Intraperitoneal organs

Everything in mesentery

Stomach, transverse colon, small intestine (digestive organs)

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Mucosa

Innermost layer
Lines alimentary canal lumen
Secretion, absorption, protection
Epithelium: rich in mucus-secreting cells
Lamina-propria: underlies the epithelium (contains capillaries)
Muscularis mucosae
Contraction of smooth muscle influences diameter ONLY

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Submucosa

Vascular layer (blood and nerve supply) --> supplies surrounding tissues of GI tract wall
Lymphatics and glands

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Muscularis externa

When present, is a double layer
Segmentation + peristalsis
Inner circular muscle layer
Outer longitudinal muscle layer
Exception: in stomach (triple layer); oblique muscle present

Serosa

Visceral peritoneum
Outermost layer of intraperitoneal organs

Adventitia: slightly more rigid; present in esophagus only
Holes the esophagus up; fibrous CT

Splanchnic circulation

Aorta –> abdominal aorta –> arteries

Celiac trunk

Serves upper abdominal cavity

Liver, stomach, spleen

Mesenteric arteries

Serves lower abdominopelvic region

Intestines

Hepatic portal circulation

Collects nutrient-rich venous blood, draining from the digestive viscera and delivers it to the liver

Intrinsic innervation (ENS)

In GI tract
Submucosal and myenteric plexuses
Any regulation within intrinsic ENS –> LOCAL

Extrinsic innervation (ENS)

Connections to CNS
Outside GI tract
Afferent visceral fibers
Sympathetic and parasympathetic branches of ANS

Parotid glands

Anterior to ear | Branches of facial nerve run through gland

Submandibular glands

Ducts run beneath mucosa of oral cavity floor

Sublingual glands

Center, under tongue (mostly mucous cells)

Serous cells

Secrete thin, watery saliva (enzymes, ions, and tiny bits of mucin)

Mucous cells

Thick, viscous saliva (mucus)

Saliva

Used to clean mouth and wet food (Starts digestion) Water, ions, digestive enzymes (defensins), mucin, lysozyme, IgA Slightly acidic

Salivary amylase:

Carb digestion

Salivary lipase

Fat digestion

Salivatory nuclei

Cluster of neurons in the medulla oblongata (brain stem) Regulation (Parasympathetic) Cranial nerve VII: facial nerve Submandibular and sublingual glands Cranial nerve IX: glossopharyngeal nerve Parotid glands

Esophageal glands

In submucosal layer | Mucus-secreting

Esophageal hiatus

Hole/opening in the diaphragm | Esophagus enters through, to abdomen

Cardial orifice

Esophagus meets stomach

Upper esophageal sphincter (UES)

Opens to allow the bolus into the stomach

Gastroesophageal sphincter (LES)

Surrounds the cardinal orifice | Only time its open, is when food is ready to enter the stomach; stretch receptor trigger opening

Deglutition

Buccal phase Pharyngeal-esophageal phase Propulsion

Buccal phase

Voluntary (in mouth) | Bolus: food that has been mechanically broken down, is shaped into a ball

Pharyngeal-esophageal phase

Involuntary Triggered by saliva or food reaching receptors in the posterior pharynx Epiglottis closes Bolus starts to move down --> esophagus

Propulsion

Movement of food (via peristalsis) | Main function of esophagus