Digestive Anatomy Flashcards
What makes up the digestive system?
- Digestive tract
- Accessory organs
What are under digestive tract?
Mouth, teeth, pharynx, esophagus, stomach, small intestine, large intestine
What are accessory organs?
- Salivary glands (parotid, sublingual and submandibular)
- Liver
- Gallbladder
- Pancreas
What makes up the abdominal cavity?
- Peritoneum
- Mesenteries
- Peritoneal cavity
What is the structure of the peritoneum?
- Parietal peritoneum (outer layer): lines the body wall
- Visceral peritoneum (inner layer): covers the surface layer of organ and continues with parietal
- Peritoneal cavity: filled with fluid (peritoneum fluid) allows organs to slide each other and along the body wall to function
What are mesenteries?
- Double layer of peritoneum –> fused back to back –> one connects to organ, one connect to the body wall
- Fold of membrane that attaches the intestine to the abdominal wall and holds it in place
What is dorsal mesentery?
- Attached to the dorsal body wall
- Dorsal: posterior part of the body (cranial + spinal)
What is ventral mesentery?
- Attached to the ventral body wall
- Ventral: anterior part of body (thoracic + abdominal + pelvic)
What are retroperitoneal organs?
- Lose their mesentery during development
- Mesentery reabsorbed and lost –> lie behind the peritoneum
- SAD PUCKER
o Suprarenal (adrenal) glands
o Aorta/IVC
o Duodenum (except the proximal 2 cm)
o Pancreas (except tail)
o Ureters
o Colon (ascending and descending)
o Kidneys
o Esophagus
o Rectum
What are intraperitoneal organs?
- Retains their mesentery, covered by visceral peritoneum
- Stomach
- 5cm-4th part of duodenum
- Jejunum
- Ileum
- Liver
- Spleen
- Cecum
- Appendix
- Transverse and sigmoid colon
- Upper third of rectum
- (intraperitoneal organs perforates can see the contents of organs spilling into peritoneal cavity eg. perforated appendicitis)
What are the subdivisions of peritoneum?
- Mesentery
- Mesocolon
- Greater Omentum
- Lesser Omentum
- Ligaments
Describe the mesentery of small intestine
- Attached to the jejunum and ileum
- Double layer peritoneum
- Have blood vessels, lymphatics
- Anchors the jejunum and ileum
What is the mesentery that covers large intestine?
Mesocolon
What is a mesocolon?
- A mesentery joining the colon to the dorsal abdominal wall
- Parts of the transverse coon
- Eg. transverse mesocolon, sigmoid mesocolon etc
What is the mesentery that covers stomach?
Omentum (2 types: greater and lesser)
Describe the omentum
- Stabilize stomach in position
- Forms a root for blood vessels, nerves and lymphatics to go between the stomach
What is the greater omentum?
- Attaches the stomach to transverse colon
- Attach from the greater curvature of the stomach and covers and hangs over the intestine
- Double sheet of peritoneum, folded on itself = 4 layers
What is the lesser omentum?
- Attaches the stomach and duodenum to liver
- Attach from lesser curvature of the stomach
- Double layer of peritoneum
What is the mesentery of liver?
- Ligaments
- Double layer folds of peritoneum
- Attach liver to surrounding organ or abdominal wall
What are the subdivisions of peritoneal cavity?
- Greater peritoneal cavity
- Lesser peritoneal cavity
What makes up the greater sac?
- Greater peritoneal cavity
What makes up the lesser sac?
- Lesser peritoneal cavity
What is the role of a peritoneal cavity?
- Divides into spaces, compartments
- Closed space –> cannot be visualize in radiology, but apparently in pathology
- Treatment for peritoneal diseases
What is the Foramen of Winslow?
- Passage between the greater and lesser sac that allows communications between the sacs
What is the structure of an alimentary canal?
- Lumen
- Wall layers
What are the wall layers of the alimentary canal?
- Mucosa, submucosa, muscularis externa, serosa
What are the special features of layers for the oesophagus and retroperitoneal organs?
- They have adventitia instead of serosa
- Wall layers: mucosa, submucosa muscularis externa and adventitia
What makes up the mucosa layer of the alimentary canal?
- epithelium
- lamina propria
- muscularis mucosae
What is the type of epithelium that lines the mucosal layer of the alimentary canal?
- Epithelium (2 main types)
o Stomach to rectum: simple columnar epithelium + cells secretes mucous and enzymes
o Esophagus to anal canal: stratified squamous non-keratinized epithelium (protection + avascular)
What is the lamina propria of the mucosal layer of the alimentary canal?
o Under epithelium lining + loose connective tissue and capillaries for nourishment + glands + lymphatic vessels
o Presence of MALT (mucosa-associated lymphoid tissue): defense against microbes entering alimentary canal
What is the muscularis mucosae of the mucosal layer of the alimentary canal?
o Smooth muscle tissue + inner circular + contraction for motility of mucous membrane –> enhancing secretion
o Protects underlying layers
o Absorb digestive products
What makes up the muscularis externa layer of the alimentary canal?
- outer longitudinal muscle
- inner circular muscle
Describe the muscularis externa layer of the alimentary canal
- Outer longitudinal muscles and inner circular muscle
o Circular: muscles in circular shape of tube (INNER)
o Longitudinal: horizontal way, straight (OUTER) - Aka muscularis propria: external to submucosa
- Provides motility in alimentary canal
- Some inner circular muscle thickens –> form anatomical sphincters –> eg. pyloric sphincter (at stomach and duodenum) and ileocecal valve (at small and large intestine), internal anal sphincter (upper part of anal canal)
o Controls passage of nutrients or waste in GI to prevent regurgitation - Between two muscle layers: have myenteric nerve plexus (motility of alimentary canal)
What makes up the serosa layer of the alimentary canal?
- Outermost layer of all intraperitoneal organs
- Contributed by visceral peritoneum
- Epithelial cells (mesothelial cells)
- Outer layers (adventitia)
o For retroperitoneal organs
o Esophagus lie in the thorax, outermost layer have adventitia
What are the intrinsic nerve plexus of the alimentary canal?
- Myenteric nerve plexus
- Submucosal nerve plexus
What is the anatomy of the oral cavity?
- Lips are lined with mucous membrane –> buccal mucosa
- Hard palate: anterior, separates oral and nasal cavity, made up of palatine bone
- Soft palate: posterior, mobile skeletal muscles separate the oropharynx and nasopharynx
o Temporary close the opening of nasopharynx, oropharynx
o Move when swallowing, close the oropharynx - Uvula: hangs from soft palate
- Vestibule: keep food between the teeth and help with speech
- Soft palate to tongue: palatoglossal fold/arch
- Palatopharyngeal arch
- In between these two arches/fold: palatine fold
- Aaaaa: soft palate goes up –> palatoglossal and palatopharyngeal folds
What makes up the tongue?
- Vascular and sensitive
- Muscular organ with interlacing bundles of skeletal muscles of intrinsic and extrinsic
- Sensory organ for taste
- Oral cavity + tongue: lined with stratified squamous non-keratinised epithelium
- Sulcus terminal
o V shape line (behind V is pharynx area, infront V is oral cavity)
o Divides tongue into anterior 2 thirds and posterior
o Separates the oral and pharynx
o Dorsal of tongue is not smooth –> aka papilla - Papilla: bumps on the tongue, all have taste buds except for filiform papillae
- 4 kinds of papilla
- Posterior of tongue –> have lymphoid follicles
o Collection of lymphoid follicles are lingual tonsils
o Extrinsic muscles: help protrude or elevate tongue, up down in out
o Intrinsic muscles: help give shape and size changes of the tongue, - Midline groove: anterior part –> separate the right and left tongue
What makes up the adult dentition?
- 32 dentitions
o 8 each side (bottom, top divide into two) (8 x 4 sides)
o 2, 1, 2, 3 (from centre to side)- 2 incisors (central and lateral)
- 1 canine
- 2 premolar (bicuspids): first and second premolars
- 3 molar (first, second and third/wisdom)
- Pulp: contains blood vessels, nerve and connective tissue
What makes up the fetus dentition?
- 20 deciduous (milk) teeth o 5 each side o 2, 1, 2 (from centre to side) - 2 incisors - 1 canine - 2 molars (first and second)
What are the corresponding glands and ducts in the oral cavity?
- 3 types and in pairs (left and right side)
- All are exocrine (have ducts)
- Parotid gland & parotid duct (or Stensen’s duct)
o Largest
o Infront of ear
o Between the masseter muscle and skin
o Open to oral vestibule, next to second upper molar
o Facial nerve pass through parotid gland
o Diseased parotid gland facial nerve is cut facial paralysis one side - Submandibular gland & submandibular duct
o Under jawline, under the chin
o Opens at the base of lingual frenulum - Sublingual gland & sublingual ducts
o Under the tongue
o Opens via 10-20 ducts into the floor of mouth
o Anterior to submandibular gland
What are the cells present at the salivary glands?
Serous, mucous
What is the role of serous cells?
- produce a watery secretion containing enzymes, ions and tiny bit of mucin
What is the role of mucous cells?
produce mucus, stringy, vicious solution
What cells can be found on the parotid and submandibular glands?
mostly serous cells
What cells can be found on sublingual glands?
mostly mucous cells
What cells can be found on buccal glands (inner side of cheeks) ?
equal serous and mucous cells
What are the functions of the pharynx, oropharynx, and laryngopharynx?
- Pharynx: transport food to esophagus (protection of airway from aspiration of food particles)
o Connects mouth to esophagus - Oropharynx and laryngopharynx: common passage for air, food and liquids
Which part of pharynx has no digestive role?
Nasopharynx
What are the components of the oesophagus?
- Starts at the neck –> crosses through thorax within mediastinum
- Presence of longitudinal muscles
- Pierces diaphragm at esophageal hiatus and enter abdomen and join at junction gastroesophageal or cardiac orifice
- Cardiac orifice: surrounded by a ring of smooth muscles aka Lower Esophageal Sphincter (LES) or cardiac sphincter
- LES: physiological sphincter
o Remains contracted and closed
o Opens to incoming food, or when swallow
o Both LES + muscular diaphragm helps keeps LES close when food is not swallowed - UES: Upper Esophageal Sphincter
o Junction of pharynx, upper end of esophagus, muscularis externa modified to form UES
o Aka cricopharyngeal sphincter
o Most narrow point of the entire alimentary canal
o Made up of skeletal muscle
What is the histology of esophagus?
- Mucosa: lined with stratified squamous NK epithelium (eat hard food)
- Submucosa: areolar connective tissue
o Had many glands that produce mucous for the rib
- Muscularis externa o Inner circular layer o Outer longitudinal layer o Upper 1/3: skeletal muscle o Middle 1/3: mixed (both skeletal and smooth) o Lower 1/3: smooth muscle
- Adventitia: fibrous connective tissue