Digestive System
List the organs of the digestive system, differentiating the alimentary canal organs from the
accessory organs
● Alimentary canal
○ Mouth
○ Oral cavity
○ Pharynx
○ Esophagus
○ Stomach
○ Small intestine (duodenum, jejunum, ileum)
○ Large intestine
○ Anus
● accessory organs
○ Tongue
○ Liver
○ Spleen
○ Gallbladder
Describe the major actions of the digestive process
● Ingestion
○ Bringing food into the digestive system
○ Initiative digestion
● Propulsion
○ Deglutition → swallowing, contains voluntary and involuntary aspects
○ Peristalsis → wave like smooth muscle contraction, involuntary
● Mechanical digestion
○ Physically breaks big pieces of food into small pieces
○ Mastication → chewing
○ Mixing → moving food around in mouth and stomach, mix with saliva/stomach
acid, stomach churns
○ Segmentation → squishing of alimentary canal tube breaks food down
● Chemical digestion
○ Uses enzymes to break polymers into monomers that can be absorbed and used
as building blocks
○ Starts in the mouth → saliva contains enzymes that break down starch
○ Does not occur in the esophagus, starch breakdown continues from mouth
○ Starts back up in stomach → stops starch breakdown and starts up protein
breakdown
○ Finishes in small intestine
● Absorption
○ Movement of digested products out of lumen of alimentary canal, through the
lining, and into blood or lymph
○ Anything in the alimentary canal is technically outside the body
, ● Defecation
○ Elimination of human waste (feces)
○ Whatever isn't absorbed is eliminated
Describe the mechanisms of control of the digestive process, differentiating short and long
reflexes
● Sensors
○ Baroreceptors → mechanical receptors that detects stretch, stretch triggers
activity
○ Chemoreceptors → chemical receptors that detect presence of proteins/lipids/etc
to initiate action
● Nerve plexuses
○ Long reflexes (extrinsic) → requires action of the central nervous system, signal
goes organ to brain to organ
○ Short reflexes (intrinsic) → action does not require CNS, signal goes organ to
organ
● Hormones
○ Signals produce in one part of the digestive tract influence another part of the
tract
○ Ex: stomach produces hormone with effects on the large intestine
● Stimuli
○ Stretch
○ Osmolarity (concentration of things)
○ pH changes
○ Presence of specific molecules (ex: protein, lipids)
● Response
○ Activate nervous system impulse
○ Activate secretion
○ Activate smooth muscle contraction → mix and move
Define mesentery and discuss its relationship to the peritoneum
● Specialized double layer visceral peritoneum
● Visceral peritoneum lines the cavity, parietal peritoneum lines the organs
● Mesentery connects to the back of abdominal cavity and holds the organs in place
● Most organs are peritoneal (encased in peritoneum) some are retroperitoneal (behind
peritoneum)
List the four tunic of the digestive tract and describe their composition and action
● Mucosa
○ Most superficial (closest to lumen)
○ Usually simple columnar epithelium
○ Contains goblet cells which secrete mucus to help movement, can also secrete
enzymes and hormones
● Submucosa
, ○ Contains blood vessels and nerve plexus
○ Made of dense irregular connective tissue
● Muscularis externa
○ Made of smooth muscle which contracts to allow segmentation and peristalsis
○ 2 layers of muscle (interna and externa)
■ perpendicular layer contracts/dilates the vessel
■ Parallel layer stretches/shortens the vessel
● Serosa
○ Another name for the visceral peritoneum
Describe the enteric nervous system
● Intrinsic nerves in alimentary canal
○ autonomic nervous system
○ Parasympathetic activates, sympathetic inhibits
● Submucosal nerve plexus
○ Present in submucosal layer
○ Stimulation causes increase causes secretion
● Myenteric nerve plexus
○ In muscle layer
○ Stimulation causes increase in muscle contraction to cause motility
Describe the anatomy and function of each organ (alimentary and accessory) of the digestive
system
● Oral (buccal) cavity
○ Has boundaries →lips in front, cheeks on side, palate on top
○ Palate
■ Roof of oral cavity, floor of the nasal cavity
■ Hard palate → front, boney, separates nasal and oral cavity, tongue
pushes against when we swallow
■ Soft palate → back, contains uvula which closes nasopharynx when we
swallow
○ Tongue
■ Muscular structure
■ Accessory organ
■ Move food around
■ Mixes food with salvia (moisten) and enzymes in saliva
■ Forms bolus (food compressed into ball) which is what gets swallowed
■ Papillae → bumps on surface of tongue
● Filiform papillae: majority, provide grip
● Fungiform papillae: contain taste buds
● Circumvallate papillae: along back of tongue
○ Salivary glands
■ Secrete saliva
■ Two types of cells
List the organs of the digestive system, differentiating the alimentary canal organs from the
accessory organs
● Alimentary canal
○ Mouth
○ Oral cavity
○ Pharynx
○ Esophagus
○ Stomach
○ Small intestine (duodenum, jejunum, ileum)
○ Large intestine
○ Anus
● accessory organs
○ Tongue
○ Liver
○ Spleen
○ Gallbladder
Describe the major actions of the digestive process
● Ingestion
○ Bringing food into the digestive system
○ Initiative digestion
● Propulsion
○ Deglutition → swallowing, contains voluntary and involuntary aspects
○ Peristalsis → wave like smooth muscle contraction, involuntary
● Mechanical digestion
○ Physically breaks big pieces of food into small pieces
○ Mastication → chewing
○ Mixing → moving food around in mouth and stomach, mix with saliva/stomach
acid, stomach churns
○ Segmentation → squishing of alimentary canal tube breaks food down
● Chemical digestion
○ Uses enzymes to break polymers into monomers that can be absorbed and used
as building blocks
○ Starts in the mouth → saliva contains enzymes that break down starch
○ Does not occur in the esophagus, starch breakdown continues from mouth
○ Starts back up in stomach → stops starch breakdown and starts up protein
breakdown
○ Finishes in small intestine
● Absorption
○ Movement of digested products out of lumen of alimentary canal, through the
lining, and into blood or lymph
○ Anything in the alimentary canal is technically outside the body
, ● Defecation
○ Elimination of human waste (feces)
○ Whatever isn't absorbed is eliminated
Describe the mechanisms of control of the digestive process, differentiating short and long
reflexes
● Sensors
○ Baroreceptors → mechanical receptors that detects stretch, stretch triggers
activity
○ Chemoreceptors → chemical receptors that detect presence of proteins/lipids/etc
to initiate action
● Nerve plexuses
○ Long reflexes (extrinsic) → requires action of the central nervous system, signal
goes organ to brain to organ
○ Short reflexes (intrinsic) → action does not require CNS, signal goes organ to
organ
● Hormones
○ Signals produce in one part of the digestive tract influence another part of the
tract
○ Ex: stomach produces hormone with effects on the large intestine
● Stimuli
○ Stretch
○ Osmolarity (concentration of things)
○ pH changes
○ Presence of specific molecules (ex: protein, lipids)
● Response
○ Activate nervous system impulse
○ Activate secretion
○ Activate smooth muscle contraction → mix and move
Define mesentery and discuss its relationship to the peritoneum
● Specialized double layer visceral peritoneum
● Visceral peritoneum lines the cavity, parietal peritoneum lines the organs
● Mesentery connects to the back of abdominal cavity and holds the organs in place
● Most organs are peritoneal (encased in peritoneum) some are retroperitoneal (behind
peritoneum)
List the four tunic of the digestive tract and describe their composition and action
● Mucosa
○ Most superficial (closest to lumen)
○ Usually simple columnar epithelium
○ Contains goblet cells which secrete mucus to help movement, can also secrete
enzymes and hormones
● Submucosa
, ○ Contains blood vessels and nerve plexus
○ Made of dense irregular connective tissue
● Muscularis externa
○ Made of smooth muscle which contracts to allow segmentation and peristalsis
○ 2 layers of muscle (interna and externa)
■ perpendicular layer contracts/dilates the vessel
■ Parallel layer stretches/shortens the vessel
● Serosa
○ Another name for the visceral peritoneum
Describe the enteric nervous system
● Intrinsic nerves in alimentary canal
○ autonomic nervous system
○ Parasympathetic activates, sympathetic inhibits
● Submucosal nerve plexus
○ Present in submucosal layer
○ Stimulation causes increase causes secretion
● Myenteric nerve plexus
○ In muscle layer
○ Stimulation causes increase in muscle contraction to cause motility
Describe the anatomy and function of each organ (alimentary and accessory) of the digestive
system
● Oral (buccal) cavity
○ Has boundaries →lips in front, cheeks on side, palate on top
○ Palate
■ Roof of oral cavity, floor of the nasal cavity
■ Hard palate → front, boney, separates nasal and oral cavity, tongue
pushes against when we swallow
■ Soft palate → back, contains uvula which closes nasopharynx when we
swallow
○ Tongue
■ Muscular structure
■ Accessory organ
■ Move food around
■ Mixes food with salvia (moisten) and enzymes in saliva
■ Forms bolus (food compressed into ball) which is what gets swallowed
■ Papillae → bumps on surface of tongue
● Filiform papillae: majority, provide grip
● Fungiform papillae: contain taste buds
● Circumvallate papillae: along back of tongue
○ Salivary glands
■ Secrete saliva
■ Two types of cells
