Embed Size (px)
Citation preview
DIGESTIVE SYSTEM
Chapter 25
DIGESTIVE SYSTEM
� Mouth
� Pharynx
� Esophagus
� Teeth
� Tongue
� Salivary glands
Digestive Tract Accessory Organs
� Esophagus
� Stomach
� Small intestines
� Large intestines
� Anus
� Salivary glands
� Pancreas
� Liver
� Gallbladder
FUNCTIONS OF DIGESTIVE SYSTEM
� Ingestion
� Digestion
� Propulsion
� Secretion
Absorption� Absorption
� Excretion
Major Subdivisions of
the Digestive Tract
Oral Cavity
Mechanical processing, moistening,
mixing with salivary secretions
Pharynx
Muscular propulsion of materials into the esophagus
Mouth
Esophagus
Transport of materials to the stomach
Accessory Organs of
the Digestive System
Salivary Glands
Secretion of lubricating fluid containing enzymes thatbreak down carbohydrates
Liver
FIGURE 25.1 COMPONENTS OF THE DIGESTIVE SYSTEM© 2015 Pearson
Education, Inc.
Stomach
Chemical breakdown of materials via acid and enzymes; mechanical processingthrough muscular contractions
Small Intestine
Enzymatic digestion and absorption ofwater, organic substrates, vitamins, and ions
Large Intestine
Enzymatic digestion and absorption ofwater, organic substrates, vitamins, and ions
Anus
Secretion of bile (importantfor lipid digestion), storageof nutrients, many othervital functions
Gallbladder
Storage and concentrationof bile
Pancreas
Exocrine cells secrete buffers and digestive enzymes; endocrine cells secrete hormones
Major Subdivisions of
the Digestive Tract
Accessory Organs of
the Digestive System
Oral Cavity
Pharynx
Esophagus
Salivary Glands
Liver
Stomach
Small Intestine
Large Intestine
Gallbladder
Pancreas
Pharyngeal
Arches
Palatoglossal
arch
Palatopharyngeal
arch
Uvula
Palatine
tonsil
Hard palate
Soft palate
FIGURE 25.5B THE ORAL CAVITY© 2015 Pearson
Education, Inc.
tonsil
Gingiva
Openings of
submandibular
ducts
Opening of parotid duct
Entrance to auditory tube
Hardpalate
Softpalate
Palatine tonsil
Uvula
Pharyngeal tonsil
FIGURE 25.5A THE ORAL CAVITY© 2015 Pearson
Education, Inc.
Hyoid bone
Palatopharyngealarch
Epiglottis
Lingual tonsil
TONGUE � Dorsum contains papillae
� Papillae contain taste
buds
� Embedded glands release
lingual lipase
� Lingual frenulum� Lingual frenulum
attaches tongue to floor of
mouth
� Tongue muscles
controlled by CN XII
Hypoglossal nerve
Muscles of the Tongue
SALIVARY GLAND
� 1. Parotid
� 2. Submadibular
� 3. Sublingual
� Produce amylase
Largest: Parotid � Largest: Parotid
Drains to mouth via
parotid duct
TEETH� Designed for mastication
� Crown: covered by enamel,
consists of dentin
(mineralized matrix) and
pulp which is highly
vascularized
� Neck : area of gingiva
� Root: consists of root canal,
artery vein, and nerve
� Apical foramen- end of root
canal
� Peridontal ligament
Deciduous Teeth Permanent Teeth
FIGURE 25.7C TEETH
Maxillary dental arcade
Hard palate
3rd Molar (17–21 yr)
2nd Molar (12–13 yr)
1st Molar (6–7 yr)
2nd Premolar (10–12 yr)
1st Premolar (10–11 yr)
Cuspid(11–12 yr)
Lateral incisor (8–9 yr)
Central incisors (7–8 yr)
The normal orientation of adult teeth. The normal range of
ages at eruption for each tooth is shown in parentheses.
c
Mandibular dental arcade
Central incisors (6–7 yr)
Lateral incisor (7–8 yr)
Cuspid (9–10 yr)
1st Premolar (10–12 yr)
2nd Premolar (11–12 yr)
1st Molar (6–7 yr)
2nd Molar (11–13 yr)
3rd Molar (17–21 yr)
THE PHARYNX
� Pharyngeal constrictors
�Push the bolus toward the esophagus
� Palatopharyngeus
�Elevates the larynx�Elevates the larynx
� Stylopharyngeus
�Elevates the larynx
� Palatal muscles
�Raise the soft palate
Palatal Muscles
Tensor velipalatini
Levator velipalatini
Laryngeal Elevators
Stylopharyngeus
PalatopharyngeusPalatopharyngeus
Pharyngeal Constrictors
Superior pharyngeal constrictor
Middle pharyngeal constrictor
Inferior pharyngeal constrictor
Esophagus
Lateral viewa
FIGURE 25.8 THE SWALLOWING PROCESS
1 Buccal Phase
Hard palate
Tongue
Epiglottis
Larynx
Soft palate
Bolus
Esophagus
2
3 Esophageal Phase
Peristalsis
© 2015
Pearson
Education,
Inc.
2 Pharyngeal Phase
Esophagus
Diaphragm
Stomach
Thoracic cavity
FIGURE 25.3A
PERISTALSIS
AND SEGMENTATION
1
Longitudinal muscle
Peristalsis
INITIAL STATE
Circular muscle
Frommouth
Toanus
Contraction ofcircular musclesbehind bolus
Contraction
2
© 2015 Pearson
Education, Inc.
2
Contraction
Contraction
Contraction oflongitudinal musclesahead of bolus
Contraction in circular muscle layer forces bolus forward
3
a Peristalsis propels materials along the length of the digestive tract by coordinated contractions of the circular and longitudinal layers.
FIGURE 25.3B
PERISTALSIS AND
SEGMENTATION
3
2
1
Segmentation
© 2015
Pearson
Education,
Inc.
b Segmentation movements primarily involve the circular muscle layers. These activities churn and mix the contents of the digestive tract, but do not produce net movement in a particular direction.
4
3
Mesenteric artery and vein
Mesentery Plica
FIGURE 25.2A HISTOLOGICAL STRUCTURE OF THE DIGESTIVE TRACT© 2015 Pearson
Education, Inc.
Mucosa
Submucosa
Muscularisexterna
Serosa(visceral
peritoneum)
THEMUCOSA
� Inner lining of digestive tract
� Mucous membrane
� Cells are stratified squamous or simple columnar
� Stratified squamous Epithelium location:
� Simple columnar Epithelium location:
� Mucosa makes up folds called plicae
� Lamina propria
THE SUBMUCOSA
�Surrounds the muscularis
mucosae
�Contains large blood vessels and
lymphaticslymphatics
�Contains submucosal plexus
(innervation of the mucosa)
MUSCULARIS EXTERNA
�Surrounds submucosa
�Mostly smooth muscle fibers
�Forms sphincters or valves
Contains myenteric plexus �Contains myenteric plexus
SEROSA (VISCERAL PERITONEUM)
�Covers the muscularis externa
THE ESOPHAGUS
� Hollow muscular tube from pharynx to stomach
� Enters peritoneal cavity by passing through
esophageal hiatus of diaphragm
� Innervated by CN X
Contains upper and lower esophageal sphincter� Contains upper and lower esophageal sphincter
� Esophageal wall made up of mucosa lining,
submucosa, smooth muscle layer (muscularis
mucosae), muscularis externa
� Does not have serosa layer
FIGURE 25.9 HISTOLOGY OF THE
ESOPHAGUS
Muscularismucosae
Mucosa
Stratified squamous epithelium
Laminapropria
© 2015
Pearson
Education,
Inc.
a Low-power view of a section through the esophagus
LM x 5
Submucosa
Muscularisexterna
The esophagus The esophageal mucosa
b The esophageal mucosa
LM x 300
Muscularismucosae
THE STOMACH
� Histology: _________,
� Gastric pits with: mucous surface cells, mucous
neck cells, parietal cells, chief cells,
enteroendocrine cells
� Regions of stomach: lesser and greater curvature,
cardia, fundus, body, and pylorus, gastric rugae
HISTOLOGY OF THE STOMACH
� Gastric pits: produce cells to continuously
replace lost stomach cells.
� Mucous surface cells
� Produce mucus to protect lining of stomach� Produce mucus to protect lining of stomach
� Mucous neck cells
� Produce mucus to lubricate food entering stomach
� Parietal cells
� Secrete intrinsic factor and hydrochloric acid
� Chief cells
� Secrete pepsinogen which converts to pepsin
� Enteroendocrine cells- produce hormones
� G cells produce hormone gastrin
FIGURE 25.12CD HISTOLOGY OF THE
STOMACH WALL
Layers of the
Stomach Wall
Mucosa
Gastric pit (opening to gastric gland)
Mucous epithelium
Muscularis mucosae
Lamina propria
Gastric pit
Gastric gland
Luminal surface
Lamina propria
Mucous neck cells
Cells of
Gastric
Glands
Parietal cells
c
Muscularis mucosae
Submucosa
Muscularis externa
Oblique muscle
Circular muscle
Longitudinal muscle
Serosa
Myentericplexus
Artery and vein
Diagrammatic view of the organization of the stomach wall. This corresponds to a sectional view through the area indicated by the box in part (b).
Lymphatic vessel
Diagrammatic view of a gastric gland and micrograph of the gastric mucosa.
d
LM x 200
G cell
Chief cells
Smooth muscle cell
Muscularismucosae
Mesenteries of the
Stomach
Lesser Omentum
Hepatogastric Ligament
Hepatoduodenal Ligament
Liver
STOMACH
Retractor
Diaphragm
Spleen
Left gastric artery
Right gastric artery
Lesser curvature
(medial surface)
Esophagus
FIGURE 25.10 ANATOMY OF THE STOMACH© 2015 Pearson
Education, Inc.
Greater Omentum
Gall bladder
Right kidney
Greater curvature
(lateral surface)
Duodenum
Longitudinal muscle layer
Circular muscle layer
Obliquemuscle layer
(overlying mucosa)
Musculature of
the Stomach
FIGURE 25.10 ANATOMY OF THE STOMACH© 2015 Pearson Education, Inc.
BLOOD SUPPLY TO STOMACH
� Three branches from celiac trunk:
� Left gastric artery
� Supplies lesser curvature and cardia
� Splenic artery� Splenic artery
� Supplies blood to fundus
� Branches and supplies greater curvature
� Common hepatic artery
� Branches and supplies greater and lesser curvatures
Celiac trunk
Inferior vena cava
Left gastric
Superior mesenteric
Inferior mesenteric
ABDOMINAL AORTA
THORACIC AORTA
Splenic
Common hepatic
FIGURE 22.15A ARTERIES OF THE ABDOMEN
© 2015
Pearson
Education,
Inc.
Left common iliac
RectalRight external iliac
Right internal iliac
Intestinal
WHICH OF THE FOLLOWING CELLS PRODUCE
GASTRIN, A SUBSTANCE THAT STIMULATES
SECRETORY ACTIVITY AND ENHANCES SMOOTH
MUSCLE ACTIVITY?
A. parietal cells
B. enteroendocrine cellsenteroendocrine cells
C. beta cells
D. chief cells
WHICH OF THE FOLLOWING CELLS PRODUCE
GASTRIN, A SUBSTANCE THAT STIMULATES
SECRETORY ACTIVITY AND ENHANCES SMOOTH
MUSCLE ACTIVITY?
A. parietal cells
B. enteroendocrine cells
C. beta cellsC. beta cells
D. chief cells
THE STOMACH AND LIVER ARE EXAMPLES
OF WHICH OF THE FOLLOWING?
A. intraperitoneal organs
B. retroperitoneal organs
C. interperitoneal organs
D. secondarily retroperitoneal organsD. secondarily retroperitoneal organs
THE PERITONEUM
� The abdominal organs lie within the peritoneal
cavity (abdominal cavity) and covered by visceral
peritoneum
� Intraperitoneal organs
� Stomach, liver, ileum, jejunum, parts of colon (transverse � Stomach, liver, ileum, jejunum, parts of colon (transverse
and sigmoid)
� Retroperitoneal organs
� Kidneys, ureters, abdominal aorta, most of duodenum,
pancreas, ascending and descending colon, and rectum
� Secondarily retroperitoneal organs
� Pancreas, duodenum
MESENTERIES
� Fused double sheets of peritoneal membrane
� Function:
� Mesentery proper suspends digestive organs except
duodenum
� Mesocolon = attaches to _large intestine___________
� Transverse mesocolon = attaches to transverse
mesocolon
� Sigmoid mesocolon = attaches to sigmoid colon
MESENTERIES CONTINUED
� Fusion fascia
� Attaches the ascending, descending, and rectum to
posterior abdominal wall
� Lesser omentum
� Mesentery that lies between the stomach and the � Mesentery that lies between the stomach and the
liver
� Greater omentum
� Mesentery extends from stomach and covers the rest
of the abdominal organs on the anterior surface
Lesser omentum
Greater omentum (cut)
Transverse mesocolon
Fusion fascia of ascending and descending colons fuses to dorsal
FIGURE 25.4D MESENTERIES© 2015 Pearson
Education, Inc.
Mesentery proper
(mesenterialsheet)
to dorsal peritoneum
Sigmoid colon
THE STOMACH AND LIVER ARE EXAMPLES
OF WHICH OF THE FOLLOWING?
A. intraperitoneal organs
B. retroperitoneal organs
C. interperitoneal organs
D. secondarily retroperitoneal organs
Mesenteric artery and vein
Mesentery Plica
Plica
Mucosal
epithelium
Lamina
propria
Mucosa
Villi
Mucosal glands
Submucosal gland
Muscularis
mucosae
Lymphatic vessel
FIGURE 25.2AB HISTOLOGICAL STRUCTURE OF THE DIGESTIVE TRACT© 2015 Pearson
Education, Inc.
Three-dimensional view of the histologicalorganization of the general digestive tube
a
Mucosa
Submucosa
Muscularisexterna
Serosa(visceral
peritoneum)
An enlarged section of the digestivetube showing the structure of a plica
Artery and vein
Submucosal
plexus
Circular muscle
layer
Myenteric plexus
Longitudinal
muscle layer
b
SMALL INTESTINE
� Approx 20 feet by 1.5-2.5 in diameter
� Duodenum
� 10 inches; receives digestive enzymes from pancreas,
bile from liver and gallbladder
� Jejunum� Jejunum
� 8 feet, site of most digestion and absorption
� Ileum
� 12 feet long
Duodenum
Jejunum
Ileum
FIGURE 25.13 REGIONS OF THE SMALL INTESTINE
© 2015 Pearson
Education, Inc.
Ileum
FIGURE 25.14A-C HISTOLOGY OF THE INTESTINAL WALL
Villi
Plica circularis
Lymphoid nodule
Layers of the
Small Intestine
Lamina propria
© 2015 Pearson
Education, Inc.
Muscularismucosae
Small Intestine
Mucosa
Submucosa
Muscularis
externa
Serosa
Submucosalplexus
Circular layer of smooth muscle
Myenteric plexus
propria
Longitudinal layer of smooth muscle
Lymphatic vessel
VenuleArteriole
FIGURE 25.14C
HISTOLOGY OF
THE INTESTINAL WALL
Goblet cell
Columnar epithelial cell
Lacteal
Nerve
Capillary network
Lamina propria
Diagrammatic viewof a single villus showing the capillary and lymphatic supply
c
Lymphatic vessel
VenuleArteriole
propria
REGIONAL SPECIALIZATIONS OF SMALL
INTESTINES
� Duodenum
� Contains duodenal submucosa glands
� Receives bile from liver and gallbladder
� Buffers and digestive enzymes from pancreas
� Jejunum� Jejunum
� Has prominent plicae and villi
� Ilium
� Contains prominent lymphoid centers called
aggregated lymphoid nodules (Peyer’s patches)
REGULATION OF SMALL INTESTINES
� Vagal (CN X) stimulation, enteroendocrine cells
of small intestines release:
� Secretin
�Causes liver to begin making bile
Causes pancreas to release buffers �Causes pancreas to release buffers
� Cholecyostokinin
�Causes pancreas to release digestive
enzymes
�Causes gallbladder to contract to release bile
�Causes hepatopancreatic sphincter to open
LARGE INTESTINES
� Approx 5 feet in length by 3 inches in diameter
� Receives blood from branches of superior and
inferior mesenteric arteries
� Function:
1.1.
2.
3.
Inferior mesenteric artery
Left colic vein
Splenic vein
Superior mesenteric artery
Inferior mesenteric vein
Aorta
Hepatic portal vein
Superior
mesenteric vein
Inferior vena cava
FIGURE 25.16A THE LARGE INTESTINE
© 2015
Pearson
Education,
Inc.
Rectum
Rectal artery
Intestinal arteries and veins
Taenia coli
Sigmoid arteries and veins
Omental appendices
THE COLON
� The wall of the colon has pouches that
allow for expansion called haustra
� Longitudinal muscles called teniae coli
aid in the process of peristalsisaid in the process of peristalsis
� The serosa of the large intestine has
numerous “flaps” of sacs of fat attached
to, extending from the intestine called
omental appendices
HISTOLOGY OF LARGE INTESTINES
� Walls are thinner than the walls of the
small intestine
� The walls lack villi
� Has numerous goblet cells� Has numerous goblet cells
� Has very distinctive intestinal crypts
�Produces lots of mucus to lubricate
undigested material
� Contains large lymphoid nodules
FIGURE 25.18A
THE WALL
OF THE
LARGE INTESTINE
Taenia coli
Omental appendices
Haustrum
Lymphoid nodule
Layers of the
Large Intestine
Mucosa
Simple columnar epithelium
Goblet cells
© 2015 Pearson
Education, Inc.
Mucosa
Submucosa
Muscularis externa
Serosa
Muscularis mucosae
Circular layer
Longitudinal layer
(taenia coli)
cells
Intestinal crypt
FIGURE 25.17
Left colic (splenic) flexure
Right colic (hepatic) flexure
Transverse colon
Haustra
Ascending colon
© 2015
Pearson
Education,
Inc.
Descending colon
Cecum
Sigmoid colon
Rectum
Major Subdivisions of
the Digestive Tract
Oral Cavity
Pharynx
Mouth
Esophagus
Accessory Organs of
the Digestive System
Salivary Glands
Liver
Stomach
Small Intestine
Large Intestine
Anus
Gallbladder
Pancreas
THE LIVER
� Largest visceral organ of the body
� Metabolic regulation
� Hematological regulation
� Bile production
FIGURE 25.21AC
Round ligament
Right hepatic duct
Cystic duct
Gallbladder
Common bile
ductLiver
Duodenum
Stomach
Pancreas
Left hepatic
duct
Common
hepatic duct
Hepatic portal vein
Common hepatic artery
© 2015 Pearson
Education, Inc.
Pancreas
Pancreas
Hepatopancreaticsphincter
Duodenal ampulla
Duodenal papilla
Intestinal lumen
Common bile duct
Pancreatic duct
Major Subdivisions of
the Digestive Tract
Oral Cavity
Pharynx
Mouth
Esophagus
Accessory Organs of
the Digestive System
Salivary Glands
Secretion of lubricating fluid containing enzymes thatbreak down carbohydrates
Liver
FIGURE 25.1 COMPONENTS OF THE DIGESTIVE SYSTEM© 2015 Pearson
Education, Inc.
Stomach
Small Intestine
Large Intestine
Anus
Secretion of bile (importantfor lipid digestion), storageof nutrients, many othervital functions
Gallbladder
Storage and concentrationof bile
Pancreas
Exocrine cells secrete buffers and digestive enzymes; endocrine cells secrete hormones
© 2015
Pearson
Education,
Inc.
FIGURE 25.19C ANATOMY OF THE LIVER
Right lobe Left lobe
Coronary ligament
Falciform
© 2015 Pearson
Education, Inc.
Falciform
ligament
Round ligament
Gallbladder
ACCESSORY GLANDULAR DIGESTIVE
ORGANS
� Anatomy of the Liver
� Falciform ligament
�Marks the boundary between the left and right lobes
�The inferior portion of the falciform ligament
becomes thick and round and is called the roundbecomes thick and round and is called the round
ligament
� The falciform ligament spreads on the surface of
the liver attaching to the inferior side of the
diaphragm
�This spreading ligament is called the coronary
ligament
HISTOLOGICAL ORGANIZATION OF THE
LIVER
� The liver is divided into approximately 100,000 liver lobules
�Each lobule is separated by the interlobular septum
�The center of each lobule consists of a �The center of each lobule consists of a vein from the hepatic portal system
�The hepatocytes are arranged in such a manner forming cellular lines extending from the central vein outward
�Spaces created between lines of hepatocytes are called sinusoids
�Sinusoids consists of capillaries leading to central vein and Kupffer cells
© 2015 Pearson
Education, Inc.
Interlobular septum
Bile duct
Branch of hepatic portal vein
Portal area
Bile ductules
FIGURE 25.21AC
Round ligament
Right hepatic duct
Cystic duct
Gallbladder
Common bile
ductLiver
Duodenum
Stomach
Pancreas
Left hepatic
duct
Common
hepatic duct
Hepatic portal vein
Common hepatic artery
© 2015 Pearson
Education, Inc.
Pancreas
Pancreas
Hepatopancreaticsphincter
Duodenal ampulla
Duodenal papilla
Intestinal lumen
Common bile duct
Pancreatic duct
GALLBLADDER
� When hepatopancreatic sphincter is closed:
� Bile enters cystic duct into gallbladder
� Gall bladder can store 40-70 ml of bile
� Water is removed to concentrate bile
If food in sm intestines is high in fat content, sm� If food in sm intestines is high in fat content, sm
intestines release __cholecystokinin_(CCK)__
� ____ cholecystokinin __________ will cause
gallbladder to release bile
Right hepatic duct
Cystic duct
Gallbladder
Common bile
Left hepatic duct
Common hepatic duct
Common bile duct
Liver
Duodenum
Stomach
Pancreas
Major Subdivisions of
the Digestive Tract
Oral Cavity
Pharynx
Mouth
Esophagus
Accessory Organs of
the Digestive System
Salivary Glands
Liver
© 2015 Pearson
Education, Inc.
Stomach
Small Intestine
Large Intestine
Anus
Gallbladder
Pancreas
Exocrine cells secrete buffers and digestive enzymes; endocrine cells secrete hormones
Abdominal aorta
Celiac trunk
Common hepatic artery
Common bile duct
Superior pancreatic artery
Lobules
Splenic artery
Tail of pancreas
FIGURE 25.22A THE PANCREAS
© 2015
Pearson
Education,
Inc.
Pancreatic duct(to greater duodenal
papilla) with common bile duct
Superior mesenteric artery
Head of pancreas
Body of pancreas
HISTOLOGY OF PANCREAS
� Consists of lobules with:
� Acinar cells:
� Produce digestive enzymes
� Enzymes travel through the pancreatic duct to the
small intestinessmall intestines
� Pancreatic islets:
� Produce hormones
� Hormones enter bloodstream to travel to target
organs
Pancreatic
duct
Acinar cells
(exocrine)
Pancreatic islet
(endocrine)
Pancreatic
acini
FIGURE 25.22B THE PANCREAS
© 2015
Pearson
Education,
Inc.
FIGURE 25.22C
THE PANCREAS
Pancreatic acini
(exocrine)
Duct
© 2015
Pearson
Education,
Inc.
LM x 120Pancreas
Pancreatic islet
(endocrine)
PANCREATIC ENZYMES (FROM ACINAR
CELLS)
� Lipases
� Carbohydrases
� Nucleases
� Proteinases
� Insulin
� Glucagon
� Somatostatin
PANCREATIC HORMONES (FROM
PANCREATIC ISLETS
REGULATION OF PANCREATIC SECRETION
� Cholecystokinin (CKK)
� From small intestines will cause pancreas to release
digestive enzymes
� Secretin� Secretin
� From small intestines will cause the pancreas to release
buffers to neutralize acidic chyme from stomach
