L31: Digestive System #1 Flashcards
what are the organs of the gastrointestinal tract?
- oral cavity
- pharynx
- esophagus
- stomach
- small intestine
- large intestine
in the Git tract wall, what pushes materials from one end to the other?
smooth muscle
what do the organs of the GI tract form?
a continuous 9-10m tube from the mouth to the anus
what are the accessory digestive organs?
- liver
- gallbladder
- pancreas
- sublingual salivary glands
what is ingestion
acquisition of nutrients
digestion?
Mechanical and chemical breakdown of
ingested food
propulsion?
Movement of food through GI tract
peristalsis and segmentation
secretion?
Release of mucins, water, acid, and enzymes
into the lumen of the digestive system
absorption?
Transport of nutrients from the digestive
system to the circulatory system
defecation?
elimination of feces
Peristalsis?
Wave muscular contraction that occurs
throughout the GI tract (similar to pushing
toothpaste through the toothpaste tube)
Segmentation?
Back-and-forth churning that occurs mainly in
the small intestine
Tonsils?
- patches of lymphatic tissue found at the entrance of the pharynx
- protection against ingested and inhaled pathogens
Enamel?
white outer surface of tooth (only in crown), calcified surface that is stronger than bone
Dentin?
surface directly beneath enamel that is less calcified, similar to bone
Pulp?
inner most part of the tooth, houses the nerve and blood supply to the tooth
CROWN?
(externally visible covered by enamel)
NECK?
(covered by gingiva, lacks enamel, not located in
alveolar bone
ROOT?
housed in alveolar bone, different teeth have different numbers of roots
what is the tongue?
Skeletal muscle and
covered by stratified
squamous epithelium
function of the tongue?
- Assistance in chewing
• Sensory analysis by touch, temperature, and taste receptors
• Secretion of mucins and the
enzyme lingual lipase that aids in breaking down the triglycerides
function of salivary glands?
- Lubricate the oral cavity & moisten food
- Dissolve chemicals that simulate the taste buds
- Anti-microbial substances
- Parasympathetic innervation simulates salivary gland secretion
parotid?
• Anteriorly to the ear
• 25-30% of the saliva passes into the oral cavity
via the parotid duct
• Glossopharyngeal nerve (CN IX)
sublingual?
Inferiorly to tongue and internal to oral mucosa
• 3-5% of saliva passes to the inferior surface of
the oral cavity via the sublingual ducts
• Facial nerve (CN VII
Submandibular?
Inferior to the mandible • 60-70% of the saliva passes to the floor of the mouth (lingual frenulum) via the submandibular duct • Facial nerve (CN VII)
action of temporalis?
TMJ elevation; Jaw closing; retraction of
the mandible; side to side movements
action of masseter?
TMJ elevation; Jaw closing; retraction and
protraction of the mandible; side to side
movements
action of medial pterygoid?
TMJ elevation; Jaw closing; side to side
movements
action of digastric?
Jaw opening; TMJ depression; larynx
elevation
action of mylohyoid?
Jaw opening; TMJ depression; floor of
mouth elevation; hyoid elevation
action of geniohyoid?
Jaw opening; TMJ depression; larynx
elevation; hyoid retraction
what are the oropharynx and laryngopharynx lined with?
nonkeratinized stratified squamous
epithelium
blood supply of pharynx?
branches of the external carotid a.
what drains the pharynx?
internal jugular veins
esophagus?
• hollow muscular tube connecting the pharynx to the stomach • 25cm long •Located within the mediastinum
what kind of muscle is the esophagus?
skeletal and smooth
role of the wall of the esophagus?
wall secretes a lubricant
functions of stomach
- Storage of digestive food
- Mechanical breakdown of
ingested food - Chemical digestion via acids and enzymes
(preliminary protein
digestion)
ingested food is then called?
chyme (viscous, acidic, soupy mixture)
lesser omemtum is attached to?
role?
- lesser curvature
- stabilises position of stomach
greater omentum is attached to?
role?
- greater curvature
- its adipose tissue protects the abdomen
role of lesser and greater omenta?
house (or convey) the blood vessels and nerves of the stomach
what makes up the small intestine?
duodenum + jejunum + ileum
role of small intestine
Important digestive and absorptive functions (carbohydrates, proteins, and fat) – Secretions and buffers provided by pancreas, and gall bladder (liver)
where does the small intestine begin and end?
Begins at pyloric sphincter (stomach/small intestine transition) and ends at Ileocecal valve (small
intestine /large intestine transition )
where does the duodenum originate?
pyloric sphincter
is the duodenum retroperitoneal?
it is Retroperitoneal apart from the most
proximal part which is intraperitoneal
how does the duodenum connect to the liver?
by the lesser omentum
what is the duodenum covered in and why?
It is covered by a lining of mucous
membrane which protects the
epithelium from the acid chyme that
comes from the stomach
what is the duodenum?
mixing bowl – chyme with bile &
pancreatic secretions
how do bile and pancreatic juice enter the duodenum?
via the duodenal papilla
Jejunum?
• Important digestive and absorptive functions (carbohydrates, proteins, and fat) • Intraperitoneal suspended by the mesentery proper
Ileum?
• Absorption of vitamin B12; salts and all products of digestion that were not absorbed by the jejunum • Intraperitoneal suspended by the mesentery proper
where does the ileum end? role?
a sphincter, the ileocecal valve, which controls the flow of materials
from the ileum into the cecum of the large intestine
what are circular folds (plicae circulares)
- To increase surface for absorption & to slow the passage of food, all parts of the small
intestine contain plicae (circulares): circular folds of the intestinal lining
-Plicae are duplications of the mucous membrane - They appear in duodenum and jejunum prominently and become less common in aboral
ileum
what are intestinal villi? role?
- finger-like projections (1mm) long
- located on mucosal surface of all parts of small intestine
- increase surface area of intestinal wall and contain intestinal cells
what are microvilli? role?
- finger-like projections of plasma membrane on apical surface of columnar epithelial cells
- increase surface area for absorption and chemical digestion
how much do plicae, villi and microvilli increase intestinal surface area?
plicae: 3 fold
villi: 30 fold
microvilli: 600 fold
what are the four columns of the large intestine
- ascending
- transverse
- descending
- sigmoid
what controls movement in the large intestine
local reflexes in the autonomic nervous system
what does gastroileal reflex result in?
accumulation of more chyme in the cecum and ascending colon
what propels fecal material towards the rectum
gastrocolic reflex controls mass movements
does the large intestine have villi?
no
in the large intestine, what absorbs nutrients not absorbed in the small intestine
simple columnar epithelial cells
role of goblet cells in large intestine
secrete mucin to lubricate undigested material
difference between muscle of internal anal sphincter and external?
internal: ring of smooth muscle
External: ring of skeletal muscle
