Lecture 22: Digestive System Flashcards
Differentiate between organs of the alimentary canal and accessory digestive organs
Two groups of organs:
- Alimentary canal ie GI tract
- digests and absorbs food
- mouth, pharynx, oesophagus, stomach, small intestine, and large intestine - Accessory digestive organs
- teeth, tongue, gallbladder
- digestive glands- salivary glands
- liver
- pancreas
Be able to label a diagram of the digestive system
Slide 4
Do it!
What are the 6 essential activities in digestion
- Ingestion
- Propulsion
- Mechanical digestion
- Chemical digestion
- Absorption
- Defection
What is the peritoneum and peritoneal cavity. What is their location and function
Peritoneum: serous membrane of the abdominal cavity
-visceral peritoneum: on external surface if most digestive organs
-parietal peritoneum: line the body wall
Peritoneal cavity:
-between the two peritoneums
-fluid lubricates mobile organs
Mesentary: is a double layer of peritoneum
-routes for blood vessels, lymphatics, and nerves
-holds organs in place and stores fat
Retroperitoneal organs lie posterior to the peritoneum
Intra peritoneal organs are surrounded by the peritoneum
Refer to slide 8 for visual
Blood supply: splanchnic circulation
What is the hepatic portal circulation
Arteries
-celiac –> hepatic, splenic, and left gastric
-inferior and superior mesenteric
The hepatic portal circulation
-drains nutrient rich blood from all digestive organs
-delivers it to the liver for processing
Histology of the alimentary canal
Four basic layers (tunics)
-mucosa (innermost)
-lines the lumen
-functions:
-secretes mucus, digestive enzymes and hormones
-absorbs end products of digestion
-protects against infectious disease
Submucosa
Muscularis externa
Serosa (outermost)
Refer to slide 11 for imageWhat is the enteric system, what’s its function?
Sensory:
-linked to the CNS via afferent visceral fibers
Motor:
-long ANS fibers synapse with enteric plexus
-sympathetic impulses inhibit secretion and motility
-parasympathetic impulses stimulate
Mouth
Oral (buccal) cavity
- bounded by lips, cheeks, palate, and tongue
- oral orifice is the anterior opening
- lined with stratified squamous epithelium
Be able to label diagram of oral cavity and pharynx slide 14
Do it!
Lips and cheeks
Contain orbicularis oris and buccinator muscles
- vestibule: recess internal to lips and cheeks, external to teeth and gums
- oral cavity proper lies within the teeth and gums
Palate:
-hard palate: palatine bones and palatine process of the maxillae
-slightly corrugated to help create friction against the tongue
Soft palate: fold formed mostly of skeletal muscle
-closes of the nasopharynx during swallowing
-uvula projects down its free edge
What is the structure and function of the tongue
Functions Include:
-mixing food during chewing
-formation of the bolus
-initiation of swallowing, speech, and taste
Intrinsic muscles: change the shape of the tongue
Extrinsic muscles: alter the tongues position
Lingual frenulum: attachment to the floor of the mouth
Surface of tongue has papillae… Of 4 types
1. Filiform-give the tongue roughness and provide friction
2. Fungiform- scattered over the tongue
3. Circumvallate (vallate) -V shaped row in back of tongue
-these three above house tastbuds
4. Foliate- on lateral aspects of the posterior tongue
Refer to slide 18 for picture
What are the 3 salivary glands and what is their functions
(Parotid, submandibular, sublingual) Saliva: -cleanses mouth -moistens and dissolves food chemicals -aids in bolus formation -contains amylase enzymes for breakdown of starch -strong sympathetic stimulation inhibits salivation and results in dry mouth Refer to slide 21
Structure and function of teeth and their aid in digestion
Slide 23
32 permanent teeth
Incisors:
-chisel shaped for cutting
Canines: fang like teeth that tear or pierce
Premolars (bicuspids) and molars
-have broad crowns with rounded cusps for grinding or crushing
Tooth structure
Slide 25
Crown: the exposed part above the gingiva (gum)
Root: portion embedded in the jawbone
Cementum: calcified connective tissue
-covers root and attaches it to the periodontal ligament
Periodontal ligament
-forms fibrous joint called gomphosis
Dentin: bone like material under enamel
Pulp cavity: cavity surrounded by dentin
Pulp: connective tissue, blood vessels, and nerves
Root canal: extends from pulp cavity to the apical foremen of the root
Pharynx structure and function
Oropharynx and laryngopharynx
- allows passage of food, fluids and air
- skeletal muscle layer: inner longitudinal, outer pharyngeal constrictors
Esophagus
-flat muscular tube from laryngopharynx to stomach
-pierces diaphragm at esophageal hiatus
-joins stomach at the cardiac orifice
-muscularis: skeletal superiorly; smooth inferiorly
-adventitia instead of serosa
Slide 28
Stomach: gross anatomy
Slide 30
Cardiac region (cardia)
-surrounds the cardiac orifice
Fundus:
-dome-shaped region beneath the diaphragm
Body
Pyloric region: pylorus is continuous with the duodenum through the pyloric valve (sphincter)
Greater curvature: convex lateral surface
Lesser curvature: concave medial surface
Omentums:
-lesser omentum (from liver to the lesser curvature)
-greater omentum (drapes from greater curvature, and anterior to small intestine)
ANS nerve supply:
-sympathetic via splanchnic nerves and celiac plexus
-parasympathetic via vagus nerve
Blood supply:
Artery: celiac trunk
Veins if the hepatic portal system
Small intestine: gross anatomy
- major organ of digestion and absorption
-2-4m long; from pyloric sphincter to ileocecal valve
Subdivisions:
1. Duodenum (retroperitoneal)
2. Jejunum (attached posterior lay by mesentery)
3. Ileum (attached posteriorly by mesentery)
Slide 35
Duodenum:
Also be able to label diagram on slide 37
First part of small intestine
-has the bile duct and main pancreatic duct
Has the below to increase surface area for nutrient absorption
-circular folds (plicae circulares)
-villi
-microvilli
Liver
-largest gland in the body
-four lobes: right, left, caudate and quadrate
Falciform ligament:
-separates the larger right and smaller left lobes
-suspends liver from the diaphragm and anterior abdominal wall
Round ligament: (ligamentum Teres)
-what’s left of the fetal umbilical vein along free edge of falciparum ligament
Refer to slide 40
What are the associated structures of the liver?
Lesser omentum anchors liver to stomach
Portal triad: 3 components
- hepatic vein: from liver to inferior vena cava
- hepatic artery and hepatic portal vein at the porta hepatis
- bile ducts
- common hepatic duct leaves the liver
- cystic duct connects to gallbladder
- bile duct formed by union of the above 2 ducts
Bile:
- yellow-green, alkaline solution containing
- bile salts: cholesterol deriviates that function in fat emulsification and absorption
- bilirubin: pigment formed from heme
Liver microscopic anatomy:
Portal triad at each corner of lobule
- bile ducts receives bile from bile canaliculi
- portal arteriole is a branch of the hepatic artery
- hepatic venule is a branch of the hepatic portal vein
Liver sinusoids are leaky capillaries
The gallbladder
- thin walled muscular sac
- stores and concentrates bile by absorbing its water and ions
- releases bile via the cystic duct, which flow into the bile duct
Pancreas
Location
Endocrine function
Exocrine function
Location:
- deep to the greater curvature of the stomach
- head is circled by the duodenum, tail abuts the spleen
Endocrine function:
-pancreatic islets secrete insulin and glucagon
Exocrine function:
-secretes pancreatic juice: amylase, lipases
