Ch 25 Anatomy of the digestive system

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1

Dicuss the structure of the digestive system

MAIN ORGANS OF THE DIGESTIVE SYSTEM:
--MOUTH, PHARYNX, ESOPHAGUS, STOMACH, SMALL INTESTINE, LARGE INTESTINE
ACCESSORY ORGANS OF THE DIGESTIVE SYSTEM:
--SALIVARY GLANDS, TONGUE, TEETH, LIVER, GALLBLADDER, PANCREAS, APPENDIX

2

What are the primary functions of the digestive system?

Digestion: breakdown of nutrients
Absorption: Passage of nutrients into blood (majority of small intestine)
Elimination: removal of wastes from digestive system (function of large intestine)
*Purposes of digestion: 1)absorbtion 2)*metabolism

3

List and discuss the 4 layers that compose the wall of the GI tract (Digestive Tube Proper)

1. MUCOSA: Innermost (Lining)
2. SUBMUCOSA: CT (Supports); Blood Vessels and Nerves
3. MUSCULARIS: Muscle Type: Smooth; Muscle Layers (2): Circular, Longitudinal (Nerves B/T)
4. SEROSA: Outermost (Covering); AKA Visceral Peritoneum

4

Discuss the purpose of modifications of the layers of the wall of the DTP.

Layers Modified in Structure Based on Organ’s Functions

5

List and discuss the 4 structures that compose the oral cavity.

Lips, cheeks, hard and soft paltes, and tongue

6

List and discuss the 2 types of salivary glands.

A. BUCCAL GLANDS
‑ See cheeks
‑ Contribute less than 5% of the total volume of saliva
B. PAIRED SALIVARY GLANDS
‑ 3 pairs
‑ Secrete the major portion (95%) of saliva

7

Discuss in detail paired salivary glands.

1. PAROTID GLANDS‑ Located in front of and below the ears‑ The largest of the salivary glands (pyramid shaped)‑ Produce saliva that contains enzyme*, but no mucous‑ Parotid Ducts (Stensen's Ducts) drain saliva from these glands into the oral cavity
2. SUBMANDIBULAR GLANDS‑ Located just below the mandibular angle‑ Approximately the size/shape of a walnut‑ Produce saliva that contains enzymes and mucous‑ Submandibular Ducts (Wharton's Ducts) drain saliva from these glands into the floor of the oral cavity
3. SUBLINGUAL GLANDS‑ Lie below the tongue in the floor of the mouth‑ The smallest of the salivary glands‑ Produce saliva that contains only mucous‑ Sublingual Ducts drain saliva from these glands into the floor of the mouth

8

Disucss the structure of a typical tooth, including divisions.

DIVISIONS
a. CROWN
‑ Exposed portion
‑ Covered by enamel
b. NECK
‑ Narrow portion surrounded by gingivae (gums)
c. ROOT
‑ Hidden portion
‑ Fits into bone (Sockets in the maxillary and mandible bones ‑ held in sockets by periodontal membrane)

9

discuss dental tissues.

a. ENAMEL
‑ Covers the crown of the tooth
‑ The hardest and most chemically stable tissue in the body (minerals)
‑ Designed to withstand abrasion and attack by bacteria
b. DENTIN
‑ Composes the greatest portion of the tooth shell
(Softer than enamel)
‑ Covered by enamel in the crown area and cementum in the neck and root area
c. CEMENTUM‑ The outermost dental tissue in the neck and root area

10

discuss pulp cavity

-the cavity located within the dentin
-contains connective tissue, blood vessels, sensory nerves

11

Discuss deciduous teeth

‑ Total Number: 20
‑ Generally erupt between 6 ‑ 30 months (Lower before upper, usually)
‑ Generally shed between 6 ‑ 13 years
‑ Replaced by permanent teeth
‑ Names/Numbers: (Per jaw)
1) Incisors ‑ 4
a. Central ‑ 2
b. Lateral ‑ 2
2) Canines (Cuspids) ‑ 2
3) Molars ‑ 4
a. First ‑ 2
b. Second ‑ 2

12

Discuss permanent teeth

‑ Total Number: 32
‑ Generally erupt between 7 ‑ 24 years
‑ Names/Numbers: (Per jaw) (Compare to deciduous)
1) Incisors ‑ 4
a. Central ‑ 2
b. Lateral ‑ 2
2) Canines (Cuspids) ‑ 2
3) Premolars (Bicuspids) ‑ 4
a. First ‑ 2
b. Second ‑ 2
4) Molars (Tricuspids) ‑ 6
a. First ‑ 2
b. Second ‑ 2
c. Third (Wisdom Teeth) ‑ 2

13

Discuss pharynx.

‑ 3 divisions ‑ Shared organ between Respiratory and Digestive Systems

14

Discuss esophagus including extent/position, structure, and layer modifications.

A.EXTENT/POSITION
‑ Extent: From pharynx to stomach
‑ Position: Lies posterior to trachea and heart
B. STRUCTURE
‑ Collapsed tube: Opens as food passes throug
C. LAYER MODIFICATIONS
1. MUCOSA‑ Cells layered for protection from injury
2. MUSCULARIS‑ 2 layers of muscle: Inner circular and outer longitudinal ‑ 2 types of muscle: Skeletal and smooth

15

Discuss the stomach including size and postions

‑ Size: Varies according to numerous factors
1) Gender
2) Amount of distention
‑ Shape: Pouchlike ‑ can hold approx. 1 ‑ 1 1/2 liters
‑ Position: Between esophagus and small intestine in the epigastric and left hypochondriac regions (5/6 to left)

16

discuss the stomach including divisions and curves.

DIVISIONS
1. FUNDUS‑ Enlarged upper portion ‑ Lies above where esophagus opens into stomach
2. BODY‑ Central portion
3. PYLORUS‑ Lower narrow portion (Where stomach joins to smallintestine)
C. CURVES
1. LESSER CURVATURE‑ Located on upper surface of stomach (smaller)
2. GREATER CURVATURE‑ Located on lower surface of stomach (larger)

17

dicuss the stomach including sphincter muscles.

1. CARDIAC SPHINCTER‑ Located between esophagus and stomach (at entrance)
‑ Controls materials entering stomach
2. PYLORIC SPHINCTER‑ Located between stomach (pylorus) and small intestine (at exit)
‑ Controls materials exiting stomach

18

Discuss the stomach including layer modifications.

1. MUCOSA
a. RUGAE ‑ Temporary longitudinal folds of the mucous lining of the stomach‑ Allow for distention of stomach
b. GASTRIC PITS AND MUCOUS CELLS‑ Gastric pits: Depressions between rugae‑ Mucous cells: Compose the rugae and line the gastric pits
c. GASTRIC GLANDS‑ Microscopic glands located below the gastric pits, especially in fundus and body ‑ Secrete gastric juice‑ Cells of gastric glands
1. CHIEF CELLS‑ Secrete the enzyme of gastric juice
2. PARIETAL CELLS‑ Secrete the hydrochloric acid of gastric juice(Gastric juice = enzyme + hydrochloric acid)‑ Also produce Intrinsic Factor (Vitamin B12 absorption)
3. ENDOCRINE CELLS: Secrete gastrin: Hormone that stimulates secretion of GJ and Ghrelin: Hormone that stimulates appetite
2. MUSCULARIS‑ 1 type of muscle: Smooth ‑ 3 layers of muscle: Inner oblique, middle,circular,and outer longitudinal muscle layers
3. SEROSA
a. VISCERAL PERITONEUM‑ The serosa of the stomach is also known as visceral peritoneum
b. GREATER OMENTUM
c. LESSER OMENTUM‑ Extensions of visceral peritoneum

19

What are the functions of the stomach?

1. Food Reservoir
2. secretes gastric juice
3. churns and mixes food
4. secretes intrinsic
5. limted amount of absorption
6.produces gastrin
7. defense

20

Discuss the small intestine including size and position

‑ Size: Approx. 1" in diameter and 20' in length
‑ Position: Lies between stomach and large intestine

21

Discuss the divisions of the small intestine

1.DUODENUM‑ First portion of small intestine (Shaped like letter “C”)- Approx. 10” in length
2. JEJUNUM‑ Middle portion of small intestine
‑ Approx. 8' in length
3. ILEUM‑ Last portion of small intestine‑ Approx. 12' in length
*Note: There is no clear line that marks where the jejunumbecomes the ileum, regions are approximate only

22

Discuss mucosa layer divisions

a. PLICA CIRCULARES ‑ Permanent circular folds of the mucous lining of the small intestine
b. VILLI‑ Microscopic fingerlike projections; cover the surface of the plica circulares (millions) (Gives lining a velvetly appearance)
‑ Surface of each villus covered by epithelial cells(Also goblet cells)‑ Internally, each villus contains:
1) Arteriole: From the superior mesenteric artery;Carries oxygen and nutrients to cells of villus
2) Venule: Joins to the superior mesenteric vein, which then joins to the hepatic portal vein; Absorbs food molecules and carries wastes away from the cells of the villus
3) Lacteal: Absorbs fat molecules, drains into the
Thoracic Duct
c. MICROVILLI (BRUSH BORDER)
‑ Microscopic hairlike structures that cover the surface of the epithelial cells of each villus
(Epithelial cells called Brush Border Cells)‑ Brush Border Cells toward the top of each villus produce enzymes
*Note: Plica circulares, Villi, and Microvilli all increase the surface area of the small intestine hundreds of times, makes the small intestine the main site for the final stages of digestion and for absorption

23

discuss mucosa layer divison (conti)

d. CRYPTS OF LIEBERKUHN‑ Microscopic depressions located between the villi
‑ Functions:1) Mucous secretion (Goblet cells)
2) Mitosis of Brush Border Cells
3) Defense: Secretes antibacterial enzymes
e. BRUNNER'S GLANDS ‑ Microscopic mucous glands located in the mucous lining of the small intestine
f. PEYER'S PATCHES‑ Clusters of lymph nodes
located in the mucous lining of the small intestine
g. SOLITARY LYMPH NODES
‑ Single isolated lymph nodes located in the mucous lining of the small intestine

24

Discuss the muscularis and serosa layers of the small intestine

2. MUSCULARIS
‑ 1 type of muscle: Smooth
‑ 2 layers of muscle: Inner circular and outer longitudinal muscle layers
3. SEROSA (VISCERAL PERITONEUM) ‑ Assoc. with mesentary

25

Discuss the size and position of the large intestine

‑ Size: Approx. 2 1/2" in diameter and 5 ‑ 6' in length
‑ Position: Lies between small intestine and exterior of the body

26

discuss the cecum and the colon of the large intestine.

1. CECUM ‑ First portion of large intestine (2 ‑ 3")‑ Pouch located in the lower right quadrant
2. COLON ‑ Second portion of large intestine‑ Has 4 divisions
a. ASCENDING COLON: ILEOCECAL VALVE‑ First division of colon: Ascends vertically on the right side of the abdomen
‑ Ileocecal Valve‑ Valve located at Ileocecal Junction‑ Function: Permits materials to move from ileum to large intestine, but not in the reverse direction
b. TRANSVERSE COLON: HEPATIC FLEXURE TO SPLENIC FLEXURE‑ Second division of colon: Extends horizontally across the abdomen‑ Extends from Hepatic Flexure to Splenic Flexure
c. DESCENDING COLON‑ Third division of colon: Descends vertically on the left side of the abdomen (Extends to top of pelvic bones)
d. SIGMOID COLON‑ Fourth and final division of colon‑ "S" shaped; Bends toward the left as it joins the rectum

27

Discuss the rectum

‑ Third portion of large intestine (last 7 ‑8")
a. ANAL CANAL (ANAL COLUMNS)
‑ Anal Canal: Terminal inch of rectum; Contains anal columns
‑ Anal Columns: Folds of the mucous lining of anal canal; Each contains an artery and a vein; Allows for expansion (Defecation)
b. INTERNAL AND EXTERNAL ANAL SPHINCTERS
‑ Sphincters at the opening of the anal canal to the exterior
‑ Internal: Smooth muscle
‑ External: Skeletal muscle
‑ Involved in defecation
c. ANUS: Opening of rectum to exterior

28

Dicuss layer modifications of the large intestine

1. MUCOSA
a. SOLITARY LYMPH NODES
b. MUCOUS GLANDS
c. ANAL COLUMNS
2. MUSCULARIS
‑ 1 type of muscle: Smooth
‑ 2 layers of muscle: Inner circular and outer
longitidinal muscle layers (Arrangement unique)
a. HAUSTRA‑ Pouches of the large intestine (Circular muscle)
b. TAENIA COLI‑ 3 tapelike strips of the large intestine(Longitudinal muscle)
*Note: Haustra and Taenia Coli give the large intestine a "puckered" appearance
c. INTERNAL/EXTERNAL ANAL SPHINCTERS
3. SEROSA (VISCERAL
PERITONEUM) ‑ Assoc. with transverse mesocolon

29

Discuss the vermiform appendix.

‑ Wormlike, 3-4” in length
‑ Joins to the cecum about 1" below the Ileocecal Valve
‑ Function uncertain: May serve as a breeding area for the normal flora of the large intestine

30

Define peritoneum and list and define the 2 layers of peritoneum

‑ The membrane of the abdomen (1 continous sheet)
A. LAYERS
1. PARIETAL‑ Lines the wall of the abdominal cavity
2. VISCERAL‑ Covers organs in the abdominal cavity

31

Discuss 5 extensions of peritoneum

B. EXTENSIONS OF PERITONEUM‑ The peritoneum extends in places and helps to hold abdominal organs in place
1. MESENTARY ‑ An extension of parietal peritoneum from the lumbar region of the posterior abdominal wall‑ Extends to between the loops of the small intestine(fan‑shaped)‑ Holds the small intestine to the posterior abdominal wall and allows free movement of each coil of the small intestine
‑ Continous with the visceral peritoneum of the small intestine
2. TRANSVERSE MESOCOLON‑ An extension of parietal peritoneum from the posterior abdominal wall (less extensive than mesentary)‑ Extends to the transverse colon and large intestine‑ Holds the transverse colon and LI to the posterior abdominal wall‑ Continous with the visceral peritoneum of the large intestine
3. GREATER AND LESSER OMENTUM‑ Greater Omentum‑ An extension of visceral peritoneum from the greater curvature of the stomach‑ Hangs over the intestines in a double fold (“LaceApron”) Function: Protection – In inflammation, the greater
omentum envelops the inflamed area and “walls it off”from the rest of the abdomen
‑ Lesser Omentum‑ An extension of visceral peritoneum from the lesser curvature of the stomach to the liver (Holds stomach to liver)
4. FALCIFORM LIGAMENT ‑ An extension of parietal peritoneum from the anterior abdominal wall
‑ Holds the liver to anterior abdominal wall
‑ Divides liver into left and right main lobes

32

Discuss the liver's location and size

‑ Location: Lies under the diaphragm in the epigastric and right hypochondriac regions of the abdomen
‑ Size: Largest gland in the body (Exocrine gland); Weighs approx. 3 ‑ 4 lbs.

33

Discuss the liver lobes

‑ Liver contains 2 major lobes (left and right)separated by falciform ligament
1. LEFT: Makes up approx. 1/6 of the liver
2. RIGHT (3): Makes up approx. 5/6 of the liver;Subdivided into 3 lobes: 1) Right Lobe Proper, 2) Caudate Lobe, 3) Quadrate Lobe

34

What are hepatic lobules?

HEPATIC LOBULES "Structural Units of the Liver"
‑ Each lobe is divided into lobules by blood vessels and fibrous tissue
‑ Each lobule is a tiny cylinder that contains 5 ‑ 6 sides
‑ Each lobule consists of 3 major structures

35

What are the three major structures that compose hepatic lobules?

hepatic cells, blood vessels, ducts

36

What are hepatic cells?

‑ Liver cells
‑ Lie in sheets that radiate outward from center of
lobule

37

Discuss blood vessels of the liver

a. BRANCHES OF HEPATIC ARTERY AND HEPATIC PORTAL VEIN
‑ Both carry blood into the liver
‑ Hepatic Artery:Branches from the Celiac Artery, Carries oxygenated blood into the liver
‑ Each lobule contains 5-6 branches of the Hepatic Artery at its outer edges
‑ Hepatic Portal Vein:Carries unoxygenated blood into the liver(Hepatic Portal Circulation)
‑ Each lobule contains 5-6 branches of the Hepatic Portal Vein at its outer edges(Interlobular Veins)
b. BRANCH OF HEPATIC VEIN (CENTRAL VEIN)
‑ Hepatic Veins: Carry unoxygenated blood out of the liver,Join to the IVC
- Each Lobule Contains 1 branch of Hepatic Vein
(Central Vein)
- Blood flow through liver: From Hepatic Artery branches and Hepatic Portal Vein branches à Sinusoids à Central Vein à Hepatic Vein à IVC
- As blood flows through sinusoids:
1) Microorganisms removed, old RBC’s destroyed
(Sinusoids lined with monocytes (macrophages))
2) Toxins detoxified
3) Certain vitamins and excess nutrients removed to be stored, metabolized

38

Discuss hepatic ducts

‑ Hepatic Ducts are part of the duct system for the transport of bile
‑ Each lobule contains 5-6 branches of L or R Hepatic Ducts located at its outer edges (Interlobular Bile Ducts)
*Note: Flow of bile is as follows:
Bile secreted by Hepatic Cells à Bile Canaliculi à
Branches of L or R Hepatic Ducts à L or R Hepatic Ducts

39

Discuss bile ducts

‑ The duct system for the transport of bile
1. FROM LIVER
a. LEFT AND RIGHT HEPATIC DUCTS
‑ Emerge from the undersurface of the liver
b. COMMON HEPATIC DUCT
‑ Left and Right Hepatic Ducts join to form the Common Hepatic Duct
2. FROM GALLBLADDER: CYSTIC DUCT‑ The duct from the gallbladder
3. COMMON BILE DUCT‑ The Common Hepatic Duct merges with the Cystic Duct to form the Common Bile Duct‑ The Common Bile Duct opens into the duodenum at the major duodenal papilla

40

What are the functions of the liver

‑ The liver has over 500 functions!
1. DETOXIFICATION‑ Hepatic cells inactivate poisons (chemical reactions)
2. BILE SECRETION ‑ Liver cells secrete approx. 1 pint of bile per day(Used in the digestion and absorption of fats)
‑ Major components of bile:
1) Bile Salts: Functional component
2) Bile Pigments: Pigments derived from the breakdown of hemoglobin; Gives bile its characteristic color
3) Cholesterol
3. METABOLISM OF PROTEINS, FATS, CARBOHYDRATES
4. STORAGE OF IRON AND SOME VITAMINS‑ Vitamins A, B12, and D
5. PRODUCTION OF PLASMA PROTEINS

41

Dicuss gallbladder size and location

‑ Size: The gallbladder is a pear‑shaped sac
‑ Location: Lies on the undersurface of the liver

42

Discuss gallbladder structure

‑ The wall of the gallbladder consists of 3 layers
1) Outer Layer: Covering; Visceral Peritoneum
2) Middle Layer: Smooth Muscle
3) Inner Layer: Mucous Lining; Arranged in Rugae

43

what are the functions of the gallbladder

1. STORAGE OF BILE
‑ The gallbladder stores bile (approx. 30 ‑ 50 ml) that enters by way of the Hepatic and Cystic Ducts
2. CONCENTRATION OF BILE
‑ The gallbladder concentrates bile 5 ‑ 10 times
3. EJECTION OF BILE
‑ During digestion, the gallbladder contracts and ejects concentrated bile into the duodenum to assist in fat digestion and absorption (Hormone
controlled)

44

discuss the pancreas size and location

‑ Size: Elongated (6 ‑ 9 "), grayish pink in color
‑ Location: Head and neck lie in the "C" of the
duodenum, the body extends horizontally behind the stomach, and the tail touches the spleen

45

discuss the structure of the pancreas

- The pancreas is a dual gland (Both exocrine and
endocrine)
1. EXOCRINE GLANDULAR TISSUE (Most abundant)
a. ACINAR UNITS‑ The cells release their secretions into microscopic ducts that eventually join to the Pancreatic Duct
b. PANCREATIC DUCT
‑ The main duct of the pancreas
‑ Extends the length of the pancreas
‑ Collects secretions from acinar units
‑ Joins to the Common Bile Duct
2. ENDOCRINE GLANDULAR TISSUE : PANCREATIC ISLETS
a. ALPHA CELLS
b. BETA CELLS

46

What are the functions of the pancreas

1. EXOCRINE PORTION: ACINAR UNITS SECRETE PANCREATIC JUICE
2. ENDOCRINE PORTION
a. ALPHA CELLS: SECRETE GLUCAGON
‑ Hyperglycemic Hormone: Stimulates Glycogenolysis and Gluconeogenesis
b. BETA CELLS: SECRETE INSULIN
‑ Hypoglycemic Hormone: Promotes Glucose entry into Cells and Glucose Catabolism