1. Small Intestine
The small intestine is a tubular organ that extends from the ___________________________ to the beginning of the __________________________________
It _______________ digestion of the nutrients in chyme, absorbs products of digestion, and transports the remaining residue to the large intestine
It consists of three parts that include:
__________________________________
The jejunum and ileum are suspended by the mesentery
The greater omentum drapes over the large intestine

2. Parts of the Small Intestine
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Stomach
Duodenum
Jejunum
Ascending colon
Cecum
Mesentery
Appendix
Ileum

3. Liver Stomach Gallbladder Transverse colon underneath Greater omentum
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Liver
Stomach
Gallbladder
Transverse colon
underneath
Greater
omentum

4. Structure of the Small Intestinal Wall
Tiny projections of the mucosa (intestinal ______________) greatly increase the __________________________
Each villus consists of simple columnar epithelium with a core of blood vessels, a lacteal (lymph capillary), and nerve fibers
Columnar cells’ free surfaces have microvilli
Intestinal glands/crypts of Lieberkühn are located between bases of villi
Plicae circulares are circular folds of mucosa

5. Structure of the Small Intestinal Wall
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Lumen
Simple columnar
epithelium
Villus
Lacteal
Intestinal
gland
Villus
Blood capillary
network
Goblet cells
Intestinal gland
© The McGraw-Hill Companies, Inc./Al Telser, photographer
Arteriole
Venule
Lymph vessel

6. b: © The McGraw-Hill Companies, Inc./Al Telser, photographer
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Cytoplasm of
epithelial cell
Microvilli
Lumen
Microvilli
Cell membrane
Mitochondrion
Golgi apparatus
Nucleolus
Rough
endoplasmic
reticulum
Nucleus
(a)
(b)
b: © The McGraw-Hill Companies, Inc./Al Telser, photographer

7. Gross Anatomy of Small Intestine

8. (a) Plicae circulares Villi Submucosa Circular muscle Muscular layer
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(a)
Plicae
circulares
Villi
Submucosa
Circular muscle
Muscular
layer
Longitudinal muscle
Serosa
(b)

9. Secretions of the Small Intestine
In addition to mucous-secreting goblet cells, there are many specialized mucous-secreting glands (________________________) that secrete a thick, alkaline mucus in response to certain stimuli
Enzymes in the membranes of the microvilli include:
___________________ – breaks down peptides into amino acids
Sucrase, maltase, lactase – break down disaccharides into monosaccharides
________________ – breaks down fats into fatty acids and glycerol
Hormones secreted by small intestine (covered in previous slides)
Enterokinase – converts trypsinogen to trypsin
______________ – hormone that inhibits acid secretion by stomach
_____________________________________ – hormone that inhibits gastric glands, stimulates pancreas to release enzymes in pancreatic juice, and stimulates the gallbladder to release bile
Secretin – stimulates the pancreas to release bicarbonate ions in pancreatic juice

10. Regulation of Small Intestinal Secretions
Regulation of small intestine secretion occurs by:
_________________ secretion is stimulated by the presence of chyme in the small intestine
Distension of the intestinal wall activates nerve plexuses in the wall of the small intestine
Parasympathetic reflexes triggering the release of intestinal _____________________________

12. Absorption of the Small Intestine
Villi increase the ___________________ for absorption
Small intestine absorption is so effective that very little absorbable material reaches the organ’s distal end, noting that:
______________________ and amino acids absorb:
Through facilitated diffusion and active transport
Absorbed into blood
______________________ and glycerol absorb by:
Several steps involved as noted
Absorbed into lymph and blood
Electrolytes and _________________________ absorb:
Through diffusion, osmosis, and active transport

14. Fats collect in clusters encased in protein to form chylomicrons
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Fats collect in clusters
encased in protein to
form chylomicrons
Nucleus 4
Chylomicrons
leave epithelial cell
and enter lacteal 2
Fatty acids are
used to synthesize
fats in endoplasmic
reticulum
Chylomicrons 5
Lymph in lacteal
transports chylomicrons
away from intestine 1
Fatty acids
resulting from fat
digestion enter
epithelial cell
Fatty acids
Endoplasmic
reticulum
Lymph
Epithelial
cell
Lacteal
Lumen of
intestine
To blood

15. Movements of the Small Intestine
The small intestine carries on mixing movements that include:
____________________________ – pushing movements that propel chyme
____________________________ – ring-like contractions that can move chyme back and forth
If small intestine becomes over distended or irritated, a strong peristaltic rush may sweep contents quickly into large intestine, resulting in ______________________________
Ileocecal sphincter joins small intestine to large intestine

16. Large Intestine
The large intestine is named because of its ______________

17. Parts of the Large Intestine
It has five parts that include:
Cecum
____________________________
Ascending, transverse, descending and sigmoid
Rectum
Anal canal
_______________________ – surrounded by internal and external anal sphincters
_________________________ is attached to cecum and contains lymphatic tissue

18. Parts of the Large Intestine
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Muscular layer
Mucous membrane
Serous layer
Transverse colon
Hepatic flexure
Splenic
flexure
Ascending colon
Tenia coli
Epiploic
appendage
Descending colon
Ileum
Ileocecal sphincter
Orifice of appendix
Haustra
Cecum
Appendix
Rectum
Sigmoid colon
Anal canal

19. Structure of the Large Intestinal Wall
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Lumen
Mucosa
Submucosa
Muscular layer
Serosa
© Ed Reschke/Peter Arnold

20. Functions of the Large Intestine
Has little or no ________________ function
_______________ water and electrolytes
Secretes ______________ – many tubular mucous glands in mucosa
Houses intestinal flora
Forms _____________
Carries out defecation
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Lumen of
large
intestine
Goblet
cells
© Ed Reschke

21. Movements of the Large Intestine
Movements of the large intestine are __________________ to those of the small intestine
It is slower and less frequent than that of the small intestine
Movements include:
Mixing movements
Peristalsis
______________________________ usually follow meals
The defecation reflex relaxes the internal anal sphincter and then the external anal sphincter

22. Animation: Reflexes in the Colon
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23. Feces
________________________ are composed of materials not digested or absorbed, and include:
Water
Electrolytes
Mucus
Bacteria
Bile pigments altered by bacteria provide the color
The pungent __________________ is produced by bacterial compounds including:
Phenol
Hydrogen sulfide
Indole
Skatole
Ammonia

24. Generalities Food usually leaves the stomach in ______________ hours
_________________________ – a nutrient that the body cannot synthesize but must be obtained from a balanced diet

25. Lifespan Changes
Changes to the digestive system are slow and slight, and eventually include:
____________________________ may become sensitive
____________________________ may recede
Teeth may loosen, break or fall out
________________________ may become more frequent
Nutrient absorption __________________________
Accessory organs age but typically not necessarily in ways that effect health