ANA110 Exam 3: The Digestive System

Function of the digestive system

Digest/absorb nutrients

List the stages of the digestive system

1. Ingestion

2. Propulsion

3. Digestion

4. Absorption

5. Defecation

Ingestion

bringing in food in the mouth

Propulsion

Peristalsis in the pharynx through the digestive tract

Digestion

Proximal digestive tract, stomach through duodenum

Absorption

2/3 of SI and part of colon

Defecation

Getting rid of waste products

Macronutrients

Body requires large amounts

Examples of macronutrients

Carbohydrates, lipids, proteins

Micronutrients

Body requires small amounts

Micronutrients examples

Vitamins and minerals

Phytochemicals

Plant-based nutrients

Proximal digestive tract

Closer to mouth

Distal digestive tract

Closer to anus

Alimentary digestive organs

Directly contribute to the movement of food

List the alimentary organs

Oral cavity, esophagus, stomach, SI, colon, rectum

List the accessory organs

Salivary glands, liver, gallbladder, pancreas, vermiform appendix

List the mucosal layers from superficial to deep

Serosa, longitudinal muscle, circular muscle, submucosa, mucosa

List the layers of mucosa from superficial to deep

Muscularis mucosa, lamina propria, epithelium

Visceral serosa

Covers the organ itself

Parietal serosa

Lines the cavity

Submucosa tissue

Very loose areolar connective tissue

Why is submucosa made up of areolar c.t.?

So things can filter through but be held together

Myenteric plexus

Muscle nerves, parasympathetic ANS

Mucosa-associated lymphatic tissue (MALT)

Tiny lymph nodes

Longitudinal muscle layer

Shortens digestive tract

Circular muscle layer

Around, cinches it closed

Which organ has 3 muscularis layers?

Stomach, increases degree of freedom for movement

Which organ has 1 muscularis layer?

Colon

Peritoneum

Double-layered serous structure

Double-layered function

Allows organ movement while also granting significant structural support

Visceral peritoneum

Covers individual organs

Parietal peritoneum

Covers the abdominopelvic cavity

Retroperitoneal organs

Behind peritoneum but inside abdominopelvic cavity, covered only anteriorly by peritoneum

Examples of retroperitoneal organs

Duodenum and pancreas

Omenta

2 large folds of peritoneum

Functions of omenta

Support and anchor organs, provide protection from daily trauma

Omenta contain

Visceral fat, blood and lymphatic vessels, nerves

List the omenta

Greater and lesser omentum

Mesentary

Suspend organs from posterior abdominal wall

Function of mesentary

Gives structure to most of the intestines

Mesentery contains

Blood and lymphatic vessels and nerves

Anterior oral cavity

Oral orifice and lips

Posterior oral cavity

Oropharynx

Superior oral cavity

Hard and soft palates

Hard palate

Rigid surface for tongue to force food against while chewing

Soft palate

Closes off and protects nasopharynx while swallowing

Inferior oral cavity

Tongue

Lingual frenulum

Anchors tongue inferiorly and limits posterior movement

The tongue innervation

Cranial Nerve XII (glossopharyngeal)

Taste buds

Foliate papillae, vallate papillae, fungiform papillae, filiform papillae

Which papillae cannot taste?

Filiform papillae, texture info, cranial nerve V

Teeth

Mechanical digestion, mastication, accessory organ

Teeth are located:

Each in its own alveolar socket in the maxilla or mandible

2 sets of teeth

1. Deciduous (baby) teeth (20)

2. Permanent teeth (28-32)

Deciduous teeth distribution

2 incisor, 1 canine, 0 premolar, 2 molar

Permanent teeth

2 incisor, 1 canine, 2 premolar, 3 (or 2) molar

External, protective components of teeth

Enamel and cementum

Internal, living components of teeth

Dentin (shock absorption) and pulp cavity

Salivary glands function

Produce and release saliva

Why are salivary glands exocrine?

They use ducts and secrete saliva

List the salivary glands

Parotid gland, submandibular gland, sublingual gland

Parotid gland

Cranial Nerve IX

Submandibular and sublingual gland

Cranial nerve VII, connected by ducts

Saliva in chemical digestion

Salivary amylase and lingual lipase

Salivary amylase

Carbohydrate digestion

Lingual lipase

Goes away around age 1-2 and breaks down lipids

Saliva in mechanical digestion

Water moistens food

Oral/buccal phase

Only voluntary phase, pushes food to back of throat

Pharyngeal phase

Opens upper esophageal sphincter and epiglottis folds over larynx

Esophageal Phase

Involuntary, peristalsis squeezes bolus down to stomach

Pharynx shape

Funnel-shaped tubes

Pharynx goes from…

Internal nares to esophagus posteriorly and larynx anteriorly

Nasopharynx function

Only respiration

Oropharynx and Laryngopharynx function

Both respiration and digestion

Deglutition

Swallowing

Esophagus

Collapsible tube composed of smooth muscle

Esophagus connects

Pharynx to stomach

Esophageal mucosa

Secretes mucous for lubrication and eases food movement

Esophageal mucosa DOESN’T

Secrete enzymes or facilitate absorption

Upper esophageal sphincter

Connects pharynx to esophagus

Lower esophageal sphincter

Connects esophagus to stomach, prevents acid reflux

Hiatal hernia

Stomach pushes into thoracic cavity

Esophageal hiatus

Opening in diaphragm, at T10

Descending aorta hiatus

At T12

Inferior Vena Cava Hiatus

At T10

Gastroesophageal junction

Esophagus ends, esophagus meets stomach at cardiac region at lower esophageal sphincter

Lower esophageal sphincter is a ____ sphincter

Physiologic sphincter, no thick appearance but acts like a sphincter

Stomach location

Just inferior to diaphragm

Stomach connects

Esophagus to duodenum

Stomach muscularis layer

Additional muscle layer whose fibers run in an oblique orientation

Mucosa folds into

Ruggae, useful for mechanical digestion

Ruggae

Agitates the bolus to break it up exposing more food to chemicals

Food enters the stomach at

Gastroesophageal junction

Chyme exits the stomach at

Pyloric sphincter

Chyme travels through stomach in

40 minutes to a few hours

Stomach pH

1.5-2.5

Stomach produces

Enzymes and HCl

Purpose of stomach enzymes and HCl

Chemical digestion and innate immunity

Acidic environment of stomach purpose

Prevents infection and activates enzymes