digestive systems

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Human AnatomyHuman Anatomy

Digestive System

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15a

Stomach AnatomyStomach Anatomy

“J” shaped flat bag Located in epigastric, left hypochondriac

regions Food enters through gastroesophageal

(cardiac) sphincter

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Figure 14.4a

15b


Regions of the stomach Cardiac region Fundus Body Pylorus – terminal end

Food empties into the small intestine at the pyloric sphincter

16a


Rugae – internal folds of the mucosa External regions

Lesser curvature Greater curvature

16b


Layers of peritoneum attached to the stomach Lesser omentum Greater omentum

Contains fat to insulate, cushion, and protect abdominal organs

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Figure 14.4a

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Stomach FunctionsStomach Functions

Acts as a storage site for food Chemical digestion of protein begins Delivers chyme (processed food) to the

small intestine

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Specialized Mucosa of the StomachSpecialized Mucosa of the Stomach

Simple columnar epithelium Gastric glands – secrete gastric juice Chief cells – produce pepsinogens Parietal cells – produce hydrochloric acid Endocrine cells – produce gastrin

20a

Structure of the Stomach MucosaStructure of the Stomach Mucosa

Gastric pits

formed by folded mucosa

Glands and specialized cells

are deeper in the gastric gland region

20b

Structure of the Stomach MucosaStructure of the Stomach Mucosa

Figure 14.4b, c

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Small IntestineSmall Intestine

Site of nutrient absorption Muscular tube ~20’ long extends from pyloric sphincter to

ileocecal valve Suspended from the posterior

abdominal wall by mesentery

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Subdivisions of the Small IntestineSubdivisions of the Small Intestine

Duodenum Attached to the stomach Curves around the head of the pancreas

Jejunum Second portion, ~8’

Ileum Longest portion, ~10’

23a

Chemical Digestion in the Small Chemical Digestion in the Small IntestineIntestine

Enzymes mix with chyme. Come from: Intestinal cells Pancreas (also adds HCO3

-) Bile enters from the gall bladder

23b

Chemical Digestion in the Small Chemical Digestion in the Small IntestineIntestine

Figure 14.6

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Villi of the Small IntestineVilli of the Small Intestine

Fingerlike structures formed by the mucosa

Provide more surface area

Figure 14.7a

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Structures Involved in Absorption of Structures Involved in Absorption of NutrientsNutrients

Absorptive cells Blood capillaries Lacteals (specialized

lymphatic capillaries)

Figure 14.7b

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Folds of the Small IntestineFolds of the Small Intestine

Called circular folds or plicae circulares Submucosal specialization

has Peyer’s patches collections of lymphatic tissue

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Large IntestineLarge Intestine

Larger in diameter, but shorter than the small intestine ~6’ long

Has subdivisions Named for direction of food movement

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Figure 14.8

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Functions of the Large IntestineFunctions of the Large Intestine

Absorption of water Eliminates indigestible food as feces Does not participate in digestion Goblet cells produce mucus for

lubrication

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Functions of the Large IntestineFunctions of the Large Intestine

Contains many bacteria (mostly E. coli) Bacteria digest our wastes

Produce vitamins, amino acids Vits. B, K

We absorb their “wastes”

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Structures of the Large IntestineStructures of the Large Intestine

Cecum – saclike first part Appendix

Accumulation of lymphatic tissue that may become inflamed (appendicitis)

Hangs from the cecum

30b

Structures of the Large IntestineStructures of the Large Intestine

Colon Ascending Transverse Descending Sigmoid (S-shaped)

Rectum Anus – external body opening

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Figure 14.8

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Modifications to the Longitudinal Modifications to the Longitudinal Layer of MuscleLayer of Muscle

Smooth muscle reduced to three bands (taeniae coli)

Muscle bands are shorter than colon Walls are formed into pouches called

haustra

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Accessory Digestive OrgansAccessory Digestive Organs

Salivary glands Teeth Pancreas Liver Gall bladder

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Organs of the Digestive SystemOrgans of the Digestive System

Figure 14.1

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Salivary GlandsSalivary Glands

Salivary glands: 3 pairs Parotid glands – located anterior to ears Submandibular glands Sublingual glands

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SalivaSaliva

Mixture of mucus and serous fluids Helps to form food into a bolus Contains salivary amylase

starch digestion Dissolves chemicals for taste buds We produce ~1 liter/day

35a

TeethTeeth

Function to masticate (chew) food Humans have two sets

Deciduous (baby or milk) teeth 20 teeth are fully formed by age two

35b

TeethTeeth

Permanent teeth Replace deciduous teeth beginning ~6

years of age A full adult set is 32 teeth

some people do not have wisdom teeth

36a

Classification of TeethClassification of Teeth

Incisors (2) Canines (1) Premolars (2) Molars (3)

Same number and type of teeth in each “quadrant” so….

“Dental Formula”: 2-1-2-3

36b

Classification of TeethClassification of Teeth

Figure 14.9

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LiverLiver

Largest gland in the body Located in right hypochondriac region Four lobes Suspended by the falciform ligament Connected to gall bladder via common

hepatic duct

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Primary Function of LiverPrimary Function of Liver

Produces bile for fat emulsification Composition: water, plus…

Bile salts Bile pigment (mostly bilirubin) Cholesterol Phospholipids Electrolytes

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Role of the Liver in MetabolismRole of the Liver in Metabolism

Final metabolism of most food Detoxifies drugs and alcohol Degrades hormones Produces cholesterol, blood proteins Regulates distribution of nutrients

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Gall BladderGall Bladder Sac attached to inferior surface of liver Stores, concentrates bile Bile enters duodenum in the presence

of fatty food Requires hormonal signals, autonomic

innervation Gallstones can cause blockages

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PancreasPancreas

Exocrine function: Produces digestive enzymes Enzymes: secreted into duodenum Bicarbonate ions: neutralize acidic chyme

Endocrine products of pancreas Insulin Glucagon

digestive systems

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