Lab 5 Digestion and Hormones of

Digestion

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Figure 23.1 Alimentary canal and related accessory digestive organs.

Mouth (oral cavity)

Tongue*

Esophagus

Liver*

Gallbladder*

Small

intestine

Salivary

glands*

Pharynx

Stomach

Pancreas*

Large

intestine

(Spleen)

Parotid gland

Sublingual gland Submandibular gland

Duodenum

Jejunum

Ileum

Anus

Transverse colon

Descending colon

Ascending colon

Cecum

Sigmoid colon

Rectum

Appendix

Anal canal 7/16/2015 2

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Figure 23.2 Gastrointestinal tract activities.

Ingestion

Mechanical

breakdown

Digestion

Propulsion

Absorption

Defecation

Food

Pharynx

Esophagus • Chewing (mouth)

• Swallowing (oropharynx) • Peristalsis (esophagus, stomach, small intestine, large intestine)

Stomach

Lymph vessel

Small intestine

Large intestine

Blood vessel

Mainly H2O

Feces

Anus

• Churning (stomach) • Segmentation (small intestine)

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Figure 23.7a Anatomy of the oral cavity (mouth).

Palatoglossal arch

Soft palate

Hard palate Oral cavity

Palatine tonsil

Tongue

Oropharynx

Lingual tonsil

Epiglottis

Hyoid bone

Laryngopharynx

Esophagus

Trachea

Uvula

Sagittal section of the oral cavity and pharynx 7/16/2015 4

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Figure 23.13 Deglutition (swallowing). Bolus of food

Tongue

Pharynx

Epiglottis

Glottis

Trachea

During the buccal phase, the upper esophageal sphincter is contracted. The tongue presses against the hard palate, forcing the food bolus into the oropharynx.

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Uvula

Bolus

Epiglottis

Esophagus

The pharyngeal-esophageal phase begins as the uvula and larynx rise to prevent food from entering respiratory passageways. The tongue blocks off the mouth. The upper esophageal sphincter relaxes, allowing food to enter the esophagus.

The constrictor muscles of the pharynx contract, forcing food into the esophagus inferiorly. The upper esophageal sphincter contracts (closes) after food enters.

Peristalsis moves food through the esophagus to the stomach.

The gastroesophageal sphincter surrounding the cardial oriface opens, and food enters the stomach.

Relaxed muscles

Circular muscles contract

Bolus of food

Longitudinal muscles

contract

Gastroesophageal sphincter closed

Relaxed muscles

Circular muscles contract

Gastroesophageal sphincter opens

Upper esophageal sphincter

Bolus

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4

3

5

Stomach

Slide 1

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Figure 23.14a Anatomy of the stomach. Cardia

Esophagus

Muscularis

externa

Lesser

curvature

Duodenum

Pyloric sphincter

(valve) at pylorus

Pyloric canal

Pyloric antrum

Greater curvature

Rugae of mucosa

Lumen

Body

Serosa

Fundus

• Oblique layer • Circular layer

• Longitudinal layer

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Digestive Processes in the Stomach

• Physical digestion

• Denaturation of proteins by HCl

• Enzymatic digestion of proteins by pepsin (and milk protein by rennin in infants)

• Lingual lipase digests some triglycerides before digested as any other protein

• Delivers chyme to small intestine

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Figure 23.19 Deglutition (swallowing). Slide 1

Pyloric valve closed

Pyloric valve slightly opened

Pyloric valve closed

Grinding: The most

vigorous peristalsis and

mixing action occur close to

the pylorus.

Retropulsion: The pyloric

end of the stomach acts as a

pump that delivers small amounts

of chyme into the duodenum,

simultaneously forcing most of its

contained material backward into

the stomach.

2 Propulsion: Peristaltic

waves move from the fundus

toward the pylorus.

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Figure 23.1 Alimentary canal and related accessory digestive organs.

Mouth (oral cavity)

Tongue*

Esophagus

Liver*

Gallbladder*

Small

intestine

Salivary

glands*

Pharynx

Stomach

Pancreas*

Large

intestine

(Spleen)

Parotid gland

Sublingual gland Submandibular gland

Duodenum

Jejunum

Ileum

Anus

Transverse colon

Descending colon

Ascending colon

Cecum

Sigmoid colon

Rectum

Appendix

Anal canal 7/16/2015 9

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Figure 23.29a Gross anatomy of the large intestine.

Right colic (hepatic) flexure

Transverse colon

Superior mesenteric artery

Ascending colon

IIeum

IIeocecal valve

Cecum

Appendix

Left colic (splenic) flexure

Transverse mesocolon

Epiploic appendages

Descending colon

Cut edge of mesentery

Tenia coli

Sigmoid colon

Rectum

Anal canal External anal sphincter

Haustrum

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Right and left hepatic ducts of liver

Common hepatic duct

Bile duct and sphincter

Accessory pancreatic duct

Tail of pancreas

Pancreas

Jejunum

Main pancreatic duct and sphincter

Head of pancreas Hepatopancreatic ampulla and sphincter Duodenum

Mucosa with folds

Gallbladder

Major duodenal papilla

Cystic duct

Figure 23.21 The duodenum of the small intestine, and related organs.

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Figure 23.28 Mechanisms promoting secretion and release of bile and pancreatic juice. Slide 1

Chyme enter -ing duodenum causes duodenal enteroendocrine cells to release cholecystokinin (CCK) and secretin.

CCK (red dots) and secretin (yellow dots) enter the bloodstream.

CCK induces secretion of enzyme-rich pancreatic juice. Secretin causes secretion of HCO3

− -rich pancreatic juice.

Bile salts and, to a lesser extent, secretin transported via bloodstream stimulate Liver to produce bile more rapidly.

CCK (via blood stream) causes gallbladder to contract and Hepatopancreatic Sphincter to relax. Bile Enters duodenum.

During cephalic and gastric phases, vagal Nerve stimu- lates gallbladder to contract weakly.

CCK secretion

Secretin secretion

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3

4

5

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