Mouth (oral cavity)

Tongue

Esophagus

Liver

Gallbladder

Anus

DuodenumJejunumIleum

Small intestine

Parotid glandSublingual glandSubmandibulargland

Salivaryglands

Pharynx

StomachPancreas(Spleen)

Transverse colonDescending colonAscending colonCecumSigmoid colonRectumVermiform appendixAnal canal

Largeintestine

Glands in submucosa

Submucosa

LumenMucosa-associatedlymphoid tissue

Duct of gland outsidealimentary canal

Gland in mucosa

NerveArteryVein

Lymphaticvessel Mesentery

Intrinsic nerve plexuses• Myenteric nerve plexus• Submucosal nerve plexus

Mucosa• Epithelium• Lamina propria• Muscularis mucosae

Muscularis externa

• Longitudinal muscle • Circular muscleSerosa• Epithelium• Connective tissue

Frommouth

(b) Segmentation: Nonadjacent segments of alimentary tract organs alternately contract and relax, moving the food forward then backward. Food mixing and slow food propulsion occurs.

(a) Peristalsis: Adjacent segments ofalimentary tract organs alternately contractand relax, which moves food along the tractdistally.

UvulaSoft palate Palatoglossal arch

Palatine tonsil

Hard palate

Oral cavity

Tongue

Lingual tonsilOropharynx

EpiglottisHyoid bone

Laryngopharynx

Esophagus

Trachea

Sagittal section of the oral cavity and pharynx

Crown

Neck

Root

EnamelDentinDentinal tubulesPulp cavity (containsblood vessels and nerves)Gingiva (gum)

Cementum

Root canalPeriodontalligament

Apical foramen

Bone

UvulaPalatine tonsil

Sublingual foldwith openings ofsublingual ducts

Tongue

Upper lip

Lower lip

VestibuleGingivae (gums)

Gingivae (gums)

Hard palate

Soft palate

Lingual frenulum

Opening ofsubmandibular duct

Palatine raphe

Inferior labialfrenulum

Posterior wallof oropharynx

Palatopharyngealarch

Superior labialfrenulum

Palatoglossal arch

Tongue

Trachea

Pharynx

Epiglottis

Glottis

Bolus of food

Epiglottis

Esophagus

Uvula

Bolus

Bolus

Relaxed muscles

Circular musclescontract

Bolus of food

Longitudinal musclescontract

Stomach

Relaxedmuscles

Gastroesophagealsphincter opens

Gastroesophagealsphincter closed

Upper esophageal sphincter iscontracted. During the buccal phase, thetongue presses against the hard palate,forcing the food bolus into the oropharynxwhere the involuntary phase begins.

Food is movedthrough the esophagusto the stomach byperistalsis.

The gastroesophagealsphincter opens, and foodenters the stomach.

The uvula and larynx rise to prevent foodfrom entering respiratory passageways. Thetongue blocks off the mouth. The upperesophageal sphincter relaxes, allowing foodto enter the esophagus.

The constrictor muscles of thepharynx contract, forcing foodinto the esophagus inferiorly. Theupper esophageal sphinctercontracts (closes) after entry.

1 2

4

3

5

Tongue

Trachea

Pharynx

Epiglottis

Glottis

Bolus of food

Upper esophageal sphincter is contracted. Duringthe buccal phase, the tongue presses against the hardpalate, forcing the food bolus into the oropharynxwhere the involuntary phase begins.

1

Epiglottis

Esophagus

Uvula

Bolus

The uvula and larynx rise to prevent food fromentering respiratory passageways. The tongue blocksoff the mouth. The upper esophageal sphincterrelaxes, allowing food to enter the esophagus.

2

Bolus

The constrictor muscles of the pharynx contract,forcing food into the esophagus inferiorly. The upperesophageal sphincter contracts (closes) after entry.

3

Relaxed muscles

Bolus of food

Stomach

Circular musclescontract

Longitudinal musclescontract

Gastroesophagealsphincter closed

Food is moved throughthe esophagus to thestomach by peristalsis.

4

Relaxedmuscles

Gastroesophagealsphincter opens

The gastroesophagealsphincter opens, and foodenters the stomach.

5

Cardia

Esophagus

Pyloric sphincter(valve) at pylorus

Pyloriccanal

Pyloricantrum

Rugae ofmucosa

Body

Lumen

Serosa

Fundus

Lessercurvature

Greatercurvature

Muscularis externa • Longitudinal layer • Circular layer • Oblique layer

Duodenum

Liver

Lesser omentumGallbladder

StomachDuodenum

Transverse colon

Small intestine

Cecum

Urinary bladder

Figure 23.25c

(c)

Interlobular veins(to hepatic vein) Central vein

Sinusoids

Portal triad

Plates ofhepatocytes

Portal vein

Fenestratedlining (endothelial cells) of sinusoids

Bile duct (receivesbile from bile canaliculi)

Bile duct

Portal arteriolePortal venuleHepatic

macrophagesin sinusoid walls

Bile canaliculi

Jejunum

Mucosawith folds

Cystic duct

DuodenumHepatopancreaticampulla and sphincter

Gallbladder

Right and lefthepatic ducts of liver

Bile duct and sphincter

Main pancreatic ductand sphincter

PancreasTail of pancreas

Head of pancreas

Common hepatic duct

Major duodenalpapilla

Accessory pancreatic duct

Left colic(splenic) flexure

Transversemesocolon

Epiploicappendages

Descendingcolon

Teniae coli

Sigmoidcolon

Cut edge ofmesentery

External anal sphincter

Rectum

Anal canal

Right colic(hepatic) flexure

Transversecolon

Superiormesentericartery

Haustrum

Ascendingcolon

IIeum

IIeocecal valve

Vermiform appendix

Cecum

Glucose

Phase 1SugarActivationGlucose is activated by phosphorylationand converted to fructose-1, 6-bisphosphate

Fructose-1,6-bisphosphate

2 ADP

Carbon atom

Phosphate

GlycolysisElectron trans-port chain and oxidativephosphorylation

Krebscycle

Fructose-1,6-bisphosphate

Dihydroxyacetonephosphate

Glyceraldehyde3-phosphate

Phase 2SugarCleavageFructose-1, 6-bisphosphate is cleaved into two 3-carbon fragments

Carbon atom

Phosphate

Glycolysis Electron trans-port chain and oxidativephosphorylation

Krebscycle

To Krebscycle

(aerobicpathway)

2

2

4 ADP

2 Lactic acid

2 Pyruvic acid

Dihydroxyacetonephosphate

Glyceraldehyde3-phosphate

Phase 3Sugar oxidationand formationof ATPThe 3-carbon frag-ments are oxidized (by removal of hydrogen) and 4 ATP molecules are formed

Carbon atomPhosphate

2 NAD+

2 NAD+

NADH+H+

NADH+H+

Glycolysis Electron trans-port chain and oxidativephosphorylation

Krebscycle

Krebs cycle

NAD+

NAD+

GDP +

NAD+

FAD

NAD+

NADH+H+

Cytosol

Mitochondrion(matrix)

NADH+H+

FADH2

NADH+H+

Citric acid

(initial reactant)

Isocitric acid

Oxaloacetic acid

(pickup molecule)

Malic acid

Succinic acidSuccinyl-CoA

GTP

ADP

Carbon atom

Inorganic phosphate

Coenzyme A

Acetyl CoA

Pyruvic acid from glycolysis

Transitionalphase

Fumaric acid

NADH+H+

CO2

CO2

CO2

-Ketoglutaric acid

Electron trans-port chain and oxidativephosphorylation

Glycolysis Krebscycle

Via oxidativephosphorylationVia substrate-level

phosphorylation

MitochondrionMitochondrialcristaeCytosol

KrebscycleGlucose

Glycolysis

Pyruvicacid

Electron transportchain and oxidativephosphorylation

Chemical energy (high-energy electrons)

1 During glycolysis, each glucose molecule is broken down into two molecules of pyruvic acid in the cytosol.

2 The pyruvic acid then enters the mitochondrial matrix, where the Krebs cycle decomposes it to CO2. During glycolysis and the Krebs cycle, small amounts of ATP are formed by substrate-level phosphorylation.

3 Energy-rich electrons picked up bycoenzymes are transferred to the elec-tron transport chain, built into the cristae membrane. The electron transport chain carries out oxidative phosphorylation, which accounts for most of the ATP generated by cellular respiration.

Chemical energy

Krebscycle

Glycerol Fatty acids

Coenzyme A

Lipase

Oxidationin the mito-chondria

Cleavageenzymesnips off2C fragments

Glycolysis

Glyceraldehydephosphate

(a glycolysis intermediate)

Pyruvic acid

Lipids

Acetyl CoA

FAD

H2O

NAD+

NADH + H+

FADH2

ElectrontransportCholesterol

Stored fatsin adipose

tissue

Dietary fats

Glycerol

GlycolysisGlucose

Glyceraldehydephosphate

Pyruvic acid

Acetyl CoA

CO2 + H2O+

Steroids

Bile salts

Fatty acids

Ketonebodies

Triglycerides(neutral fats)

Certainaminoacids

Ketogenesis (in liver)

Catabolic reactions

Anabolic reactions

Lipogenesis

Krebscycle

Proteins

Proteins Carbohydrates Fats

Excretedin urine

Glycogen

Glucose

Glucose-6-phosphate

Glyceraldehyde phosphate

Pyruvic acid

Acetyl CoA

Amino acids

Keto acids

Triglycerides (neutral fats)

Lactic acid

Ketonebodies

Glycerol and fatty acids

NH3

Krebscycle

Urea

Food PyramidFood Pyramid