chapter 14 part a

Chapter 14: Digestive System

1.     System functions:

a.    Ingestion – taking in food

b.    Digestion – breaking down food both physically and chemically

c.    Absorption – movement of nutrients into the bloodstream

d.    Defecation – rids the body of indigestible waste

2.    Two groups of organs:

a.    Alimentary canal – (gastrointestinal or GI tract)- continuous coiled hollow tube

                                          i.    Mouth

                                        ii.    Pharynx

                                       iii.    Esophagus

                                       iv.    Stomach

                                         v.    Small intestine

                                       vi.    Large intestine

                                      vii.    Anus

b.    Accessory organs – “branches” off of alimentary canal

                                          i.    Salivary glands

                                        ii.    Pancreas

                                       iii.    Liver

                                       iv.    Gall bladder

3.    Mouth – oral cavity

a.    Anatomy

                                          i.    Lips (labia) – protect the anterior opening

                                        ii.    Cheeks – form the lateral walls of mouth

                                       iii.    Hard palate – forms the anterior roof

                                       iv.    Soft palate – forms the posterior roof

                                         v.    Uvula – fleshy projection of the soft palate

                                       vi.    Vestibule – space between lips externally and teeth and gums internally

                                      vii.    Oral cavity proper – area contained by the teeth

                                     viii.    Tongue – attached at hyoid bone and styloid processes of the skull, and by the lingual frenulum to the floor of the mouth

                                       ix.    Tonsils – bacteria filters

1.     Palatine – on palate

2.    Lingual – base of tongue

b.    Physiology

                                          i.    Mastication – (chewing) of food

                                        ii.    Mixing chewed food with saliva

                                       iii.    Tongue

1.     Initiates swallowing by the tongue

2.    Taste

4.    Pharynx = throat

a.    Anatomy

                                          i.    Nasopharynx –not part of the digestive system

                                        ii.    Oropharynx- posterior to oral cavity

                                       iii.    Laryngopharynx-below the oropharynx and connected to the esophagus

b.    Physiology serves as a passageway for air and food

                                          i.    Mixed passageway

                                        ii.    Food movement –food is propelled to the esophagus by two muscle layers. Food movement is by alternating contractions of the muscle layers by (peristalis)

1.     Circular layer-outer layer

2.    Longitudinal-inner layer

3.    Peristalsis- food movement is by altering contractions of muscle layers

5.    Esophagus

a.    Anatomy

                                          i.    Length

                                        ii.    Runs from

b.    Physiology

                                          i.    Peristalsis

                                        ii.    Food only

6.    Common structure of alimentary canal organs

a.    Four layers

                                          i.    Mucosa- inside layer

                                        ii.    Submucosa-just beneath the mucosa, soft connective tissue with blood vessels, nerve endings, glands, and lymphatics

                                       iii.    Muscularis externa- smooth muscle, inner circular layer, outer longitudinal layer

                                       iv.    Serosa-outermost layer of the wall contains fluid-producing cells

1.     Visceral peritoneum-outermost layer that is continuous with the innermost layer

2.    Parietal peritoneum-innermost layer that lines the abdominopelvic cavity

7.    Nervous system control

a.    Two divisions of the autonomic(automatic) nervous system-cant control

                                          i.    Submucosal nerve plexus

                                        ii.    Myenteric nerve plexus

                                       iii.    Function is to regulate mobility and secretory activity of the GI tract organs in coordinated way

8.    Stomach

a.    Anatomy

                                          i.    Located

                                        ii.    Cardioesophageal sphincter

                                       iii.    Pyloric sphincter

                                       iv.    Regions

1.     Cardiac

2.    Fundus

3.    Body

4.    Pylorus

5.    Rugae

6.    External

a.    Greater curvature

b.    Lesser curvature

7.    Peritoneum attachment

a.    Lesser omentum

b.    Greater omentum

b.    Physiology

                                          i.    Food & water storage

                                        ii.    Water and some chemical absorption

                                       iii.    Mechanical digestion

                                       iv.    Chemical digestion

1.     Stomach mucosa

                                         v.    Chyme

c.    Stomach mucosa

                                          i.    Mucosa structure:

                                        ii.    Mucous neck cells

                                       iii.    Gastric glands

1.     Chief cells

2.    Parietal cells

3.    Enteroendocrine cells

9.    Small intestine

a.    Overview

                                          i.    Body’s main organ for

                                        ii.    Site of

                                       iii.    Muscular tube

                                       iv.    Suspended from posterior abdominal wall

b.    e) Subdivisions

                                          i.    Duodenum

                                        ii.    Jejunum

                                       iii.    Ileum

c.    Chemical digestion – enzymes from:

                                          i.    Intestinal glands

                                        ii.    Pancreas

                                       iii.    Liver/gall bladder

d.    Surface area increase mainly for absorption

                                          i.    Villi (villus) – fingerlike structures formed by the mucosa

1.     Capillaries & lacteals -  for absorption

                                        ii.    Microvilli – tiny projections of the plasma membrane (create a brush border appearance)

                                       iii.    Plicae circulares – circular folds: deep folds of mucosa and sub mucosa.

10.  Large intestine

a.    Anatomy

                                          i.    Large = larger in diameter, but shorter in length than the small intestine.

                                        ii.    Frames the internal abdomen –goes along the outer edge of abdomen.

                                       iii.    No villi present-absorb water through walls

                                       iv.    Goblet cells produce alkaline mucus which lubricates the passage of feces

                                         v.    Muscularis externa = teniae coli-three bands of muscle

                                       vi.    Two common problems-diarrhea=food moves through too fast. Constipation=food moves through too slowly

b.    Cecum-saclike first part of the large intestine

c.    Appendix-no real function

                                          i.    Vestigial

                                        ii.    Location –hangs from the cecum

                                       iii.    Fatty tissue

                                       iv.    Accumulation of lymphatic tissue that sometimes becomes inflamed

d.    Colon

                                          i.    Ascending-travels up right side of abdomen

                                        ii.    Transverse-travels across the abdominal cavity

                                       iii.    Descending –travels down the left side

                                       iv.    Sigmoid –enters the pelvis

e.    Rectum-where feces is stored

f.    Anus-opening of the large intestine

                                          i.    External anal sphincter-skeletal muscle(voluntary control)

                                        ii.    Internal anal sphincter-formed by smooth muscle(involuntary)

These sphincters are normal closed except during defe