Digestive System

Front 1

Ingestion

Back 1

taking food into the mouth

Front 2

Movement of Food

Back 2

the passage of food along the gastrointestinal (GI) tract

Front 3

Digestion

Back 3

the breakdown of food by chemical and mechanical means

Front 4

Absorption

Back 4

the passage of digested food from GI tract into bloodstream (and lymph) for distribution to cells

Front 5

Defecation

Back 5

the elimination of undigested material

Front 6

DIGESTIVE SYSTEM

Back 6

Ingestion Movement of Food Digestion Absorption Defecation

Front 7

DIGESTIVE ORGANS

Back 7

Alimentary canal (GI Tract)
◦ mouth
◦ pharynx
◦ esophagus
◦ stomach
◦ small intestine
◦ large intestine

Front 8

Accessory organs

Back 8

◦ salivary glands
◦ liver
◦ gallbladder
◦ pancreas

Front 9

DIGESTIVE TISSUES

Back 9

MUCOSA
SUBMUCOSA
MUSCULARIS
SEROSA

Front 10

MUCOSA

Back 10

= innermost
} composed of epithelium + CT (areolar); and small amounts of smooth muscle
} contains many glands that secrete mucus
} functions:
◦ protection
◦ secretion
◦ absorption (of nutrients)

Front 11

SUBMUCOSA

Back 11

= beneath mucosa
} composed of areolar CT, blood vessels, lymph vessels, and nerves;
} functions:
◦ nourishment of mucosa
◦ carrying absorbed nutrients away

Front 12

MUSCULARIS

Back 12

2 layers of muscle
} circular muscle layer around submucosa
} longitudinal layer around circular layer
} function: movements of food through canal (mixing & peristalsis)

Front 13

SEROSA

Back 13

outermost layer
} visceral peritoneum
} functions:
◦ lubrication
◦ free movement of canal in abdominal cavity

Front 14

PERISTALSIS

Back 14

Smooth muscle is arranged in 2 layers at right
angles to each other:
} When circular muscles contract the lumen constricts and the organ lengthens
} When longitudinal muscles contract it shortens and dilates
} This results in a rhythmic motion called?
} This is also  how earthworms crawl

Front 15

INGESTION

Back 15

Oral cavity
} Intake of food
◦ Mechanical digestion = physical breakdown of food by tongue and teeth
Taste
} Forms bolus for swallowing
} Initiates swallowing process
◦ Chemical digestion = breakdown of molecules by enzymes

Front 16

TEETH

Back 16

First teeth (20)
} = Deciduous, baby or milk teeth
} Second teeth (32)
} = permanent, adult teeth
} Every tooth has a specific job

Front 17

Incisors (8)

Back 17

used for cutting food.

Front 18

Canines (4)

Back 18

– = cuspids
– used for tearing food.

Front 19

Premolars (8)

Back 19

– = bicuspids
– used for crushing and tearing

Front 20

Molars (12)

Back 20

– used for grinding

Front 21

TEETH

Back 21

Crown
◦ Only part normally seen
◦ Covered in enamel
} Gum line
◦ Where the tooth and the gums meet
} Root
◦ part of the tooth embedded in bone.
◦ The root makes up about two-thirds of the tooth and holds the tooth in place
} Enamel
◦ Hardest tissue in the body
} Dentin
◦ Layer of the tooth under the enamel
} Pulp
◦ Soft tissue found in the center of all teeth, where the nerve tissue and blood vessels are.

Front 22

SALIVARY GLANDS

Back 22

Basic secretory units of salivary glands = acini (clusters of cells)

Front 23

2 major types of cells in acini

Back 23

◦ Serous
– Secrete watery fluid, rich in amylase (enzyme)
◦ Mucous
– Secrete thick mucous

Front 24

3 sets of glands

Back 24

◦ Parotid
– Largest
– Mostly serous cells
◦ Submandibular
– Equal in serous and mucous cells
– More viscous secretion
◦ Sublingual
– Smallest
– Mostly mucous cells

Front 25

SALIVARY GLANDS/SALIVA
FUNCTIONS

Back 25

} Start chemical digestion of starches, amylose
} Moisten and lubricate food for swallowing
} Put food into solution for tasting
} Moisten mouth

Front 26

TEETH

Back 26

Crown
◦ Only part normally seen
◦ Covered in enamel
} Gum line
◦ Where the tooth and the gums meet
} Root
◦ part of the tooth embedded in bone.
◦ The root makes up about two-thirds of the tooth and holds the tooth in place
} Enamel
◦ Hardest tissue in the body
} Dentin
◦ Layer of the tooth under the enamel
} Pulp
◦ Soft tissue found in the center of all teeth, where the nerve tissue and blood vessels are.

Front 27

SALIVARY GLANDS

Back 27

Basic secretory units of salivary glands = acini (clusters of cells)

Front 28

2 major types of cells in acini

Back 28

◦ Serous
– Secrete watery fluid, rich in amylase (enzyme)
◦ Mucous
– Secrete thick mucous

Front 29

3 sets of glands

Back 29

◦ Parotid
– Largest
– Mostly serous cells
◦ Submandibular
– Equal in serous and mucous cells
– More viscous secretion
◦ Sublingual
– Smallest
– Mostly mucous cells

Front 30

SALIVARY GLANDS/SALIVA
FUNCTIONS

Back 30

} Start chemical digestion of starches, amylose
} Moisten and lubricate food for swallowing
} Put food into solution for tasting
} Moisten mouth

Front 31

SALIVA COMPOSITION

Back 31

99.4% water
} 0.6% includes:
◦ mucus
◦ antibodies
◦ Enzymes/amylase
◦ other

Front 32

TONGUE

Back 32

Voluntary muscle
} Functions
◦ Mechanical digestion
◦ Sense of taste
◦ Aides in swallowing
◦ Aides in speech

Front 33

SWALLOWING

Back 33

Initiated voluntarily then
proceeds automatically
} Divided in 3 phases:
◦ Buccal
– Compression of bolus against hard palate
– Tongue forces bolus into oropharynx
– Nasopharynx sealed off by uvula
◦ Pharyngeal
– Bolus moves by peristalsis
◦ Esophogeal
– Contraction of pharyngeal muscles forces bolus into esophagus
– ESOPHAGUS

Front 34

STOMACH

Back 34

Functions mainly in storing food and mixing it with gastric juice to form chyme
} Other functions include:
◦ Chemical digestion of proteins
◦ Secretion of intrinsic factor – a chemical that is necessary for vitamin B12 absorption. ( B12 is necessary for RBC synthesis)
◦ Destruction of bacteria by hydrochloric acid
◦ Absorption of water, aspirin, and alcohol

Front 35

STOMACH

Back 35

The gastric pits lead into gastric glands, which secrete the gastric juice (2-3 L/ day). The basic cell types are:
◦ Mucous neck cells –
– upper portion of gland
– Secrete acidic mucus
◦ Chief cells –secrete pepsinogen, an inactive form of pepsin (Pepsinogen is activated by HCl and by pepsin itself)
◦ Parietal cells –
– mid-portion of glands
– Secrete hydrochloric acid and intrinsic factor.
◦ Enteroendocrine cells – secrete multiple hormones into the plasma. An example is gastrin, a hormone that regulates the stomach’s motility and secretory activity.

Front 36

SMALL INTESTINE

Back 36

Site of most digestion and almost all nutrient absorption
} Longest part of the alimentary tube
} 3 sections:
◦ duodenum
◦ jejunum
◦ ileum

VILLUS/LACTEAL
} MICROVILLI

Front 37

DIGESTIVE HORMONES

Back 37

Gastrin Secretin Cholecystokinin/ CCK

Front 38

Secretin

Back 38

causes the pancreas to send out a digestive juice that is rich in bicarbonate. It stimulates the stomach to produce pepsin, an enzyme that digests protein, and it also stimulates the liver to produce bile.

Front 39

Gastrin

Back 39

causes the stomach to produce an acid for dissolving and digesting some foods. It is also necessary for the normal growth of the lining of the stomach, small intestine, and colon.

Front 40

Cholecystokinin/ CCK

Back 40

causes the pancreas to grow and to produce the enzymes of pancreatic juice, and it causes the gallbladder to empty.

Front 41

PANCREAS

Back 41

} The “double gland”
} Two major functions:
◦ Endocrine - Secrete insulin and glucagon to control blood sugar levels
– Alpha cells secrete glucagon (increase blood sugar)
– Beta cells secrete insulin (decrease blood sugar)
◦ Exocrine – Secrete pancreatic juice (1.5 L/day) to aide in digestion
– Acinar cells contribute digestive enzymes to the pancreatic juice including:
– Protein-digesting enzymes (a.k.a. proteases).
– Fat-digesting enzymes such as pancreatic lipase.
– Carbohydrate-digesting enzymes such as pancreatic amylase.
– Duct cells secrete a bicarbonate-rich solution to neutralize the acidity of the chyme

Front 42

PANCREAS
} Largest internal organ/gland in the body
} Multiple functions

Back 42

◦ Carbohydrate metabolism – storage and release of glucose
◦ Removal of drugs, toxins, and foreign chemicals from the plasma
◦ Storage of vitamins (A, D, E, and K) and minerals (iron and copper)
◦ Protein metabolism
◦ Lipid metabolism
◦ Synthesis of plasma proteins (e.g., albumin, fibrin, etc.)
◦ Phagocytosis of old RBCs and of pathogens.
◦ Production of bile (0.5-1 L/day).

Front 43

LIVER

Back 43

GALL BLADDER/BILE
} Bile = bile salts, pigments (e.g., bilirubin) and other chemicals
} made by liver
} secreted into duodenum
} Fatty chyme in SI, triggers intestinal glands to secrete cholecystokinin
} CCK causes the contraction of the gallbladder and bile to be released into the duodenum
Bile salts from liver
emulsify the fats
In a larger fat globule
only the surface lipids are exposed
to the enzymes
Lipase from the
pancreatic juice
cleave off fatty acids

Front 44

LARGE INTESTINE

Back 44

Reabsorbtion
◦ Water
◦ Vitamins – K, biotin, and B5
◦ Organic wastes
◦ Bile salts
◦ Toxins
} Defecation
◦ Mass movements of material through colon and rectum
◦ Defecation reflex triggered by distention of rectal walls

Front 45

FECES

Back 45

Composition
◦ 75% water
◦ dead bacteria
◦ living bacteria
◦ mucus
◦ undigested food residue (known as fiber)
◦ waste material from food, cellular linings, fats, salts, and substances released from the intestines (such as)
} Odor is from the bacterial action
} Color is mostly from bile pigments such as bilirubin