Download Chapter 15 The Digestive System

Chapter 24
The Digestive System
Dr Glenn Huff
Kaplan University
Anatomy and Physiology 2
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DIGESTIVE SYSTEM
• Irregular tube called
alimentary canal or
gastrointestinal (GI) tract
• Food must first be digested,
then absorbed, and later
metabolized
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Slide 3
WALL OF THE DIGESTIVE TRACT
• Digestive tract described as tube
that extends from mouth to anus
• Wall of the digestive tube is formed
by four layers of tissue:
•
•
•
•
Mucosa
Submucosa
Muscularis
Serosa
• forming folds called mesenteries
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Slide 5
MOUTH
• Roof—
• hard palate (parts of maxillary and palatine
bones)
• soft palate, an arch-shaped muscle
separating mouth from pharynx; uvula, a
downward projection of soft palate
• Floor—formed by
• tongue
• muscles;
• papillae,
• taste buds,
• lingual frenulum,
• Typical tooth
• Three main parts—crown, neck, and root
• Enamel - hardest tissue in body
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MOUTH
• Types of teeth—incisors, cuspids,
bicuspids, and tricuspids
• Twenty teeth in temporary set; - cutting first tooth 6 months;
- set complete 2 years
• Thirty-two teeth in permanent set;
6 years = first permanent
tooth;
• set complete usually between
ages of 17 and 24 years
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SALIVARY GLANDS
• Parotid glands—largest
salivary glands
• Submandibular glands—
open into mouth on either
side of frenulum
• Sublingual glands—open
into floor of mouth
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PHARYNX
• Subdivided into three
anatomical
components:
• Nasopharynx
• Oropharynx
• Laryngopharynx
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ESOPHAGUS
• Connects pharynx to
stomach
• Dynamic passageway for
food
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STOMACH
• Size—expands after large meal;
about size of large sausage when
empty
• Food enters stomach through
gastroesophageal (cardiac)
sphincter
• Pyloric sphincter muscle closes
opening between pylorus (lower part
of stomach) and duodenum
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Stomach
• Wall - smooth muscle fibers;
contractions produce churning
movements (peristalsis)
• Lining—mucous membrane;
microscopic glands that
secrete gastric juice and
hydrochloric acid into stomach;
mucous membrane lies in folds
(rugae) when stomach is empty
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SMALL INTESTINE
• Size—about 7 meters (20
feet) long but only 2 cm or
so in diameter
• Divisions
• Duodenum
• Jejunum
• Ileum
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SMALL INTESTINE
• Wall— smooth muscle fibers
• Lining—
• mucous membrane;
• microscopic glands
• villi
• (microscopic finger-shaped
projections from surface of
mucosa into intestinal
cavity)
• contain blood and lymph
capillaries
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LIVER AND GALLBLADDER
• Size and location—liver is largest
gland; fills upper right section of
abdominal cavity and extends over
into left side
• Secretes bile
• Ducts
• Hepatic
• Cystic
• Common bile
• Gallbladder
• Location—undersurface of the liver
• Function—concentrates and stores bile
produced in the liver
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PANCREAS
• Exocrine gland that lies behind
stomach
• Functions
• Pancreatic cells secrete pancreatic
juice (most important digestive juice)
into pancreatic ducts; main duct
empties into duodenum
• Pancreatic islets (of Langerhans)—
cells not connected with pancreatic
ducts; secrete hormones glucagon
and insulin into the blood
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LARGE INTESTINE
• Divisions
• Cecum
• Colon—ascending, transverse, descending,
and sigmoid
• Rectum
• Food enters through ileocecal valve;
external opening called anus
• Wall—contains smooth muscle fibers
that contract to produce churning,
peristalsis, and defecation
• Lining—mucous membrane
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APPENDIX
• Blind tube off cecum
• No important digestive
functions in humans
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PERITONEUM
• Definitions—peritoneum, serous
membrane lining abdominal cavity and
covering abdominal organs;
• parietal layer of peritoneum lines
abdominal cavity;
• visceral layer of peritoneum covers
abdominal organs;
• peritoneal space lies between parietal
and visceral layers
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Peritoneum
• Extensions—largest are the
mesentery and greater omentum
• Mesentery is extension of parietal
peritoneum, which attaches most of
small intestine to posterior abdominal
wall
• Greater omentum, or “lace apron,”
hangs down from lower edge of
stomach and transverse colon over
intestines
• X-ray studies of the GI tract—
radiopaque contrast medium used to
help visualize structures in study
images
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DIGESTION
• Definition—transforms foods into
substances that can be absorbed
and used by cells
• Mechanical digestion—
• chewing (mastication),
• swallowing (deglutition),
• peristalsis
• break food into tiny particles, mix them
well with digestive juices, and move
them along the digestive tract
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Digestion
• Chemical digestion—breaks up
large food molecules into
compounds that have smaller
molecules; brought about by
digestive enzymes
• Enzymes and chemical digestion
• Enzymes are specialized protein
molecules that act as catalysts
• Breakdown process called
hydrolysis
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DIGESTION
• Carbohydrate digestion—mainly in small
intestine
• Pancreatic amylase—breaks
polysaccharides down to disaccharides
• Intestinal juice enzymes
• Maltase—changes maltose to
glucose
• Sucrase—changes sucrose to
glucose
• Lactase—changes lactose to glucose
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DIGESTION
• Protein digestion—starts in stomach;
completed in small intestine
• Gastric juice enzyme pepsin partially
digests proteins
• Pancreatic enzyme, trypsin, continues
digestion of proteins
• Intestinal enzymes, peptidases,
complete digestion of partially digested
proteins and convert them to amino
acids
• Fat digestion
• Bile contains no enzymes but emulsifies
fats (breaks fat droplets into very small
droplets)
• Pancreatic lipase changes emulsified
fats to fatty acids and glycerol in small
intestine
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ABSORPTION
• Definition—process by which digested
food moves from intestine into blood or
lymph
• Foods and most water minerals and
vitamins are absorbed from small
intestine; some water and vitamin K
also absorbed from large intestine
• Surface area absorption
• Structural adaptations increase absorptive
surface area
• Fractal geometry—study of fragmented
geometric irregular shapes such as those
Slide 37
in
lining
of
intestine
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Next week: Urinary System, Chapter 26
Lab: Influence of Fluid Intake on Urine
Formation - Power Phys
Review time!
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Which structure prevents food or
water from entering the trachea?
A.
B.
C.
D.
E.
Arytenoid cartilage
Epiglottis
Nasopharynx
Thyroid cartilage
Paranasal sinus
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Which of the following is the
primary gas exchange site?
A.
B.
C.
D.
E.
Trachea
Bronchiole
Nasal sinuses
Alveolus
Bronchus
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The point where the trachea divides into
right and left primary bronchi is a ridge
called
A.
B.
C.
D.
E.
Carina
Secondary bronchioles
Parietal pleura
Visceral pleura
Diaphragm
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Which of the following are cells of the
alveoli that produce surfactant?
A.
B.
C.
D.
E.
Type I alveolar cells
Type II alveolar cells
Type III alveolar cells
Surface cells
Macrophages
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With which body system does the
respiratory system work to regulate
the pH of body fluids?
A.
B.
C.
D.
E.
muscular
digestive
nervous
endocrine
urinary
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Which of the following is the dominant
method of carbon dioxide transport?
A.
B.
C.
D.
Bound to hemoglobin
Bound to oxygen
Dissolved in plasma as a gas
Dissolved in plasma as bicarbonate
ions
E. Diffusion
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Exhalation begins when
A.
B.
C.
D.
Inspiratory muscles relax
Diaphragm contracts
Blood circulation is the lowest
Both Inspiratory muscles relax and
Diaphragm contracts
E. All of these choices
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