1. Chapter 26 Digestive System
Part 1
Overview, Mouth, Esophagus

2. Functions of the digestive system
Ingestion
Digestion = breakdown of food into small structures and molecules
Mechanical digestion = physical breakdown by teeth, tongue, muscles
Chemical digestion = breakdown using enzymes
Propulsion
Secretion = production and release of mucin and fluids to aid digestion
Absorption = movement of electrolytes, fats, proteins, vitamins, water across GI tract into blood and lymph vessels
Elimination = get rid of waste

3. Gastrointestinal Tract
Categories: Digestive organs
Gastrointestinal Tract
(Digestive Organs)
Oral cavity
Make up gastrointestinal (GI) tract (AKA digestive tract or alimentary canal)
oral cavity
pharynx
esophagus
stomach
small intestine
large intestine
anus
Pharynx
Esophagus
Stomach
Large intestine
Small intestine
Anus

4. Accessory Digestive Organs
Fig. 26.1
Categories: Accessory digestive organs
Accessory Digestive Organs
Parotid salivary gland
Teeth
Tongue
Not part of GI tube
Develop as outgrowths; connected to GI tube
Assist in digestion
salivary glands
teeth and tongue
liver
gallbladder
pancreas
Sublingual
salivary gland
Submandibular
salivary gland
Liver
Gallbladder
Pancreas

5. Movement within GI tract
Fig. 26.2
Relaxation
Bolus
Lumen
Wall of
GI tract
(a) Peristalsis
Wave of contraction
Movement within GI tract
Peristalsis = rhythmic formation of ripples along tube
moves material forward
like squeezing a toothpaste tube from the bottom

6. Movement within GI tract
Mixing
Further mixing
(b) Segmentation
Movement within GI tract
Segmentation = rhythmic churning and mixing of material
squeezes at multiple locations simultaneously
moves material back and forth, mixing and breaking into smaller pieces

7. Oral Cavity First site of mechanical and chemical digestion
Fig. 26.3
Superior lip
Oral Cavity
Superior labial
frenulum
Transverse
palatine folds
First site of mechanical and chemical digestion
Vestibule = space between cheeks or lips and gums
Oral cavity proper = teeth and area within
Hard palate
Soft palate
Palatoglossal arch
Uvula
Palatopharyngeal arch
Fauces
Palatine tonsil
Tongue
Salivary duct orifices
Lingual
frenulum
Sublingual
Submandibular
Teeth
Inferior labial frenulum
Gingivae
Inferior lip

8. Fig. 26.3
Oral cavity
Tongue
Vestibule
(b) Sagittal section

9. Oral Cavity: lips Cheeks end at lips
Fig. 26.3
(a) Oral cavity, anterior view
Superior lip
Cheeks end at lips
primarily formed from orbicularis oris
covered with keratinized stratified squamous epithelium
reddish hue from abundant blood vessels
Inferior lip

10. Oral Cavity: gums Gums = gingivae
Fig. 26.3
(a) Oral cavity, anterior view
Superior lip
Superior labial
frenulum
Gums = gingivae
dense irregular connective tissue, with layer of nonkeratinized stratified squamous epithelium
Labial frenulum attaches internal surfaces of lips to gingivae
Inferior labial frenulum
Gingivae
Inferior lip

11. Oral Cavity: palate Roof of oral cavity, separates from nasal cavity
Fig. 26.3
(a) Oral cavity, anterior view
Transverse
palatine folds
Roof of oral cavity, separates from nasal cavity
Hard palate = anterior 2/3
formed from maxillae and palatine bones
has transverse palatine folds that help manipulate food
Soft palate = posterior 1/3
skeletal muscle covered with nonkeratinized stratified squamous epithelium
uvula and soft palate elevate during swallow to block nasal cavity
Hard palate
Soft palate
Uvula

12. Oral Cavity: tongue Primarily skeletal muscle
Fig. 26.3
(a) Oral cavity, anterior view
Lingual
frenulum
Tongue
Primarily skeletal muscle
covered with stratified squamous epithelium
has papillae to add texture and surface area
Attached to floor of oral cavity by lingual frenulum
Helps make sounds
Manipulates and mixes food during chewing

13. Fig. 26.3
Oral Cavity: tongue
Oral cavity
Tongue
Vestibule
Lingual tonsil
Oropharynx
Uvula
Helps form chewed food into bolus, soft moist ball of food and saliva
Pushes bolus to oropharynx for swallowing
Lingual tonsils sit on posteroinferior tongue surface

14. Oral Cavity: salivary glands
Fig. 26.3
(a) Oral cavity, anterior view
Submandibular
Sublingual
Salivary duct orifices
Produce and secrete saliva
1.0 to 1.5 L per day, mostly during meals
99.5% water + small amount of amylase (breaks down starch)
contains antibodies and antibacterials
moistens food
cleans and lubricates oral cavity
dissolves food particles for tastebuds

15. Oral cavity: salivary glands
Fig. 26.4
Oral cavity: salivary glands
Parotid salivary gland
Parotid duct
A few unicellular intrinsic salivary glands within mouth
secrete lingual lipase, activated by acidic stomach to break down lipids
Most saliva produced by multicellular salivary glands
Masseter muscle
Mucosa (cut)
Sublingual ducts
Submandibular duct
Sublingual salivary gland
Submandibular salivary gland
Mylohyoid muscle (cut)
(a) Salivary glands

16. Oral cavity: salivary glands
Fig. 26.4
Oral cavity: salivary glands
Parotid salivary gland
Parotid duct
Parotid salivary glands
anterior to ear
partly overlays masseter muscle
produces 25-30% of saliva
connects to mouth through parotid duct
Masseter muscle
Mucosa (cut)
Sublingual ducts
Submandibular duct
Sublingual salivary gland
Submandibular salivary gland
Mylohyoid muscle (cut)
(a) Salivary glands

17. Oral cavity: salivary glands
Fig. 26.4
Oral cavity: salivary glands
Parotid salivary gland
Parotid duct
Submandibular salivary glands
inferior to mandible
produce 60-70% of saliva
connect to mouth through submandibular duct
Masseter muscle
Mucosa (cut)
Sublingual ducts
Submandibular duct
Sublingual salivary gland
Submandibular salivary gland
Mylohyoid muscle (cut)
(a) Salivary glands

18. Oral cavity: salivary glands
Fig. 26.4
Oral cavity: salivary glands
Parotid salivary gland
Parotid duct
Sublingual salivary glands
inferior to tongue
produces 3-5% of saliva
Masseter muscle
Mucosa (cut)
Sublingual ducts
Submandibular duct
Sublingual salivary gland
Submandibular salivary gland
Mylohyoid muscle (cut)
(a) Salivary glands

19. Oral cavity: teeth Collectively called dentition crown is exposed part
Fig. 26.5
Crown
Enamel
Collectively called dentition
crown is exposed part
neck is smaller, just within gums
root anchors tooth to bone with periodontal ligaments
fits in dental alveoli on mandible and maxillae
Gingiva
Neck
Dentin
Pulp cavity
Root canal
Root
Cementum
Periodontal
ligaments
Dental alveolus
Blood vessels
and nerves in
apical foramen

20. Oral cavity: teeth Layers of tooth enamel forms crown
Fig. 26.5
Crown
Enamel
Layers of tooth
enamel forms crown
hardest substance in body
formed of calcium phosphate
cementum is hardened layer around root
dentin forms most of mass of tooth
harder than bone
pulp cavity is center of tooth and root
Gingiva
Neck
Dentin
Pulp cavity
Root canal
Root
Cementum
Periodontal
ligaments
Dental alveolus
Blood vessels
and nerves in
apical foramen

21. Oral cavity: teeth Layers of tooth
Fig. 26.5
Crown
Enamel
Layers of tooth
Root canal opens into connective tissue through apical foramen
blood vessels and nerves pass through
Gingiva
Neck
Dentin
Pulp cavity
Root canal
Root
Cementum
Periodontal
ligaments
Dental alveolus
Blood vessels
and nerves in
apical foramen

23. Baby teeth are deciduous teeth Start to erupt at about 6 months
Fig. 26.6
Central incisor (7–9 mos.)
Lateral incisor (9–11 mos.)
Canine (18–20 mos.)
1st molar (14–16 mos.)
2nd molar (24–30 mos.)
Upper
teeth
2nd molar (20–22 mos.)
Lower
teeth
1st molar (12–14 mos.)
Canine (16–18 mos.)
Baby teeth are deciduous teeth
Start to erupt at about 6 months
incisors first
Permanent teeth eventually replace them
Wisdom teeth are 3rd molars; erupt in teens or 20s
Lateral incisor (7–9 mos.)
Central incisor (6–8 mos.)
(b) Deciduous teeth

24. Front teeth (4) are incisors
Fig. 26.6
Right Upper (Maxillary) Quadrant
Left Upper (Maxillary) Quadrant
Central incisor (7–8 yrs.)
Front teeth (4) are incisors
Canines (AKA cuspids) are sharp for puncturing and tearing
Premolars (AKA bicuspids) are used to crush and grind
Molars are thickest, for grinding and crushing
have 3+ roots
Lateral incisor (8–9 yrs.)
Canine (11–12 yrs.)
1st premolar (10–11 yrs.)
2nd premolar (10–12 yrs.)
Upper teeth
1st molar (6–7 yrs.)
2nd molar (12–13 yrs.)
3rd molar (17–25 yrs.)
Hard palate
3rd molar (17–25 yrs.)
2nd molar (11–13 yrs.)
1st molar (6–7 yrs.)
Lower teeth
2nd premolar (11–12 yrs.)
1st premolar (10–12 yrs.)
Canine (9–10 yrs.)
Lateral incisor (7–8 yrs.)
Central incisor (6–7 yrs.)
Right Lower (Mandibular) Quadrant
Left Lower (Mandibular) Quadrant
(c) Permanent teeth

25. Serous membranes Parietal peritoneum lines inside surface of body wall
Fig. 26.7
Serous membranes
Liver
Diaphragm
Stomach
Lesser omentum
Pancreas
Parietal peritoneum lines inside surface of body wall
Visceral peritoneum covers surface of internal organs
Peritoneal cavity is between layers of membrane
Duodenum
Mesocolon
Transverse colon
Jejunum
Greater omentum
Parietal peritoneum
Mesentery proper
Visceral peritoneum
Ileum
Peritoneal cavity
Rectum
Urinary bladder

26. Fig. 26.7
Serous membranes
Liver
Diaphragm
Mesenteries are folds of peritoneum around intraperitoneal GI tract organs
Greater omentum extends from greater curvature of stomach
often accumulates adipose
Lesser omentum connects lesser curvature of stomach and proximal duodenum to liver
Stomach
Lesser omentum
Pancreas
Duodenum
Mesocolon
Transverse colon
Jejunum
Greater omentum
Parietal peritoneum
Mesentery proper
Visceral peritoneum
Ileum
Peritoneal cavity
Rectum
Urinary bladder

27. Serous membranes Mesentery proper suspends small intestine
Fig. 26.7
Serous membranes
Liver
Diaphragm
Stomach
Lesser omentum
Mesentery proper suspends small intestine
full of blood vessels, lymph vessels, and nerves
Mesocolon is fold of peritoneum that attaches parts of large intestine to posterior abdominal wall
Pancreas
Duodenum
Mesocolon
Transverse colon
Jejunum
Greater omentum
Parietal peritoneum
Mesentery proper
Visceral peritoneum
Ileum
Peritoneal cavity
Rectum
Urinary bladder

28. 4 layers of tissues in GI tract
Mucosa
Fig. 26.9
Epithelium
4 layers of tissues in GI tract
variations from one organ to another
Lamina propria
Muscularis mucosae
Mesentery
Vein
Artery
Submucosa
Lymph vessel
Submucosal gland
Lumen
Blood vessel
Submucosal nerve plexus
Muscularis
Inner circular layer
Myenteric nerve plexus
Outer longitudinal layer
Serosa

29. Mucosa epithelium lining lumen
Fig. 26.9
Mucosa
Epithelium
Lamina propria
Muscularis mucosae
Mesentery
Mucosa
epithelium lining lumen
lamina propria is areolar connective tissue
muscularis mucosae
Vein
Artery
Lymph vessel
Lumen

30. Submucosa areolar or dense irregular connective tissue
Fig. 26.9
Submucosa
areolar or dense irregular connective tissue
includes mucin-secreting glands (ducts project through mucosa)
includes blood and lymph vessels, nerves
Mesentery
Vein
Artery
Submucosa
Lymph vessel
Submucosal gland
Lumen
Blood vessel
Submucosal nerve plexus

31. Muscularis 2 layers of smooth muscle
inner layer lies circumferentially; thickening makes a sphincter
outer layer lies longitudinally
Myenteric nerve plexus controls contractions
Lumen
Muscularis
Inner circular layer
Myenteric nerve plexus
Outer longitudinal layer
Fig. 26.9

32. Fig. 26.9
Serosa or adventitia
Areolar connective tissue with collagen and elastic fibers
Serosa is covered with visceral peritoneum
Adventitia is outside peritoneum
Serosa
Lumen

33. Fig. 26.9
Blood vessels, lymphatic vessels, and nerves enter from adjacent organs or mesentery
Blood vessels
fenestrated capillaries within mucosa layer
veins in mucosa anastomose in submucosa then exit
Mesentery
Vein
Artery
Lymph vessel
Lumen

34. Lymph vessels and tissues
Fig. 24.2
Lymph vessels and tissues
Lacteal is blind-end lymphatic capillaries within villus of small intestine
Absorb fats and fat-soluble vitamins
Lymphatic capillaries form lymphatic vessels outside organ walls
Many lymph nodes near organs and within mesentery
Lymph transported to cisterna chyli then thoracic duct
Interstitial fluid
Capillary bed
Venule
Lymphatic
capillaries
Tissue cells
Arteriole
Lacteals
(a) Capillary bed and lymphatic capillaries

35. (a) Pharynx and esophagus
Diaphragm
Stomach
Inferior
esophageal
sphincter
Esophageal
hiatus
Esophagus
Superior esophageal
Laryngopharynx
Oropharynx
Esophagus
Fig
~25cm long, mostly within thorax; between trachea and vertebrae
Connects to pharynx at superior esophageal sphincter
closed during inhalation
Connects to stomach at esophageal hiatus
works with diaphragm to prevent reflux from stomach

36. Acid reflux
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Reflux esophagitis is pain and irritation of esophagus from stomach acid
more common in smokers, overweight people, overeaters
Gastroesophageal reflux disease (GERD) = erosion and scarring of esophageal tissue
more advanced cases become Barrett esophagus
increases chance of cancer
Barrett
esophagus
(a) Endoscopic view of a normal
esophagus.
(b) An endoscopic view of the
esophagus shows the signs
of Barrett esophagus.

37. Esophagus does not absorb nutrients
Fig
(b) Esophagus, transverse section
Esophagus does not absorb nutrients
Mucosa has thick, nonkeratinized stratified squamous epithelium
withstands abrasions of bolus
Submucosa has lots of elastic fibers
stretches during swallowing
mucous glands provide lubricating mucus
Muscularis has two layers
skeletal and smooth muscles
skeletal muscle contracts and returns to shape faster
Mucosa
Muscularis mucosae
Submucosa
Muscularis
Adventitia
LM 11x
Stratified squamous
epithelium
Mucosa
Lamina propria
Muscularis mucosae
LM 65x
(c) Esophageal mucosa