Abdomen and GI tract Flashcards
Wall: lateral and anterior
4 muscles:
- external oblique
- internal oblique
- transversus abdominis
- rectus abdominis
Superficial layer
Skin (1), Subcutaneous tissue
Camper’s fascia, fatty (2), Scarpa’s fascia,
membranous (3)
Deep layer
Muscles (4,5,6,10) enclosed in
investing fascia
- Transversalis fascia – situated
deep to abdominal muscles (7)
- Extraperitoneal fat – variable
amount (8)
- Parietal peritoneum (9)
Vessels of Anterolateral Abdominal Wall
- Superior epigastric vessels (branches of
internal thoracic vessels) - Inferior epigastric vessels (branches of
external iliac vessels)
Muscles of Anterolateral Abdominal Wall obliques
External oblique (#4) - fibers run supero-medially, flexes and rotates the trunk, works with internal oblique
Internal oblique (#5) - fibers run perpendicular to those of external oblique.
flexes and rotates the trunk, works with external oblique
Muscles of Anterolateral Abdominal Wall: abdominis
Transversus abdominis (#6) - fibers run horizontally, no skeletal movement, horizontal orientation does not permit flexion or lateral bending, primarily raises intra-abdominal pressure
Rectus abdominis (#10) - paired muscles separated by linea alba, attachments on pubic symphysis inferiorly and XP and CC 5-7 superiorly, contained within rectus sheath, fused aponeuroses of 3 flat abdominal muscles
AM movements
Rectus abdominis- flexes the trunk
External and internal obliques- flex & rotate the trunk
Transversus abdominis- no skeletal movement, horizontal orientation does
not permit flexion or lateral bending, primarily raises intra-abdominal pressure
DS overview
alimentary canal (GI tract) - mouth, pharynx, and esophagus, stomach, small intestine, and large intestine (colon)
accessory digestive organs - teeth and tongue, salivary glands, liver, gallbladder, pancreas
Chewing apparatus
Mandible: Lower Jaw
Maxilla: Upper Jaw, Hard Palate
Mastication: mandible, chewing, mandibular branch of the trigeminal nerve (CN V3)
Chewing
Temporalis muscle – Elevates mandible; retracts mandible
Masseter muscle – Elevates mandible, limited protrusion of mandible
Lateral Pterygoid muscle – Protracts mandible; produces lateral chewing motions
Medial Pterygoid muscle – Elevates mandible (working with masseter);
provides more subtle grinding motion
Tongue
lies partly in the oral
cavity and partly in the oropharynx, taste and speech, highly mobile and assists in chewing and swallowing
Extrinsic muscles of tongue
- genioglossus – tongue protraction
- hyoglossus – tongue depression
- styloglossus – tongue retraction and elevation
Hypoglossal Nerve (motor), CN XII
Deglutition
process that transfers the food bolus from
the oral cavity (mouth) through the oro-pharynx, into the pharynx and
eventually through the esophagus into the stomach
Swallowing
- bolus of food is squeezed back into OC, pushes tongue against palate
- NP sealed off by epiglottis, larynx elevates, enlarged pharynx gets food
- pharyngeal constrictors contract, squeeze food into esophagus
- bolus of food moves down it by peristaltic contractions
Palate muscles
Tensor veli palatini: Tenses SP opens pharyngotympanic tube during swallowing
Levator veli palatini: elevates SP during
swallowing
Palatoglossus: elevates P part of tongue
Palatopharyngeal: tenses SP pulls walls of
pharynx superiorly, anteriorly and medially during swallowing
Esophagus
muscular tube propels food into stomach, pharynx continuation, descends inferior through thorax, voluntary (striated) muscle in the upper 1/3 and involuntary (smooth) muscle in the lower 1/3. A mixture of muscle fibers in middle 1/3, Vagus (CN X)
Esophagus and abdominal cavity
pierces through diaphragm, terminates at the esophago-gastric junction where contents dump into cardial portion of stomach
Stomach
Mobile intraperitoneal muscular organ, S part of peritoneal cavity, mechanical breakdown of food churned into chyme by peristalsis, chemical breakdown of proteins via acids and enzymes, gastric fluids slowly convert food mass into a liquid mixture which passes to the duodenum
Stomach features
- cardiac region – at the junction with the esophagus
- fundus – the stomach’s dome
- pylorus – termination of the stomach
- greater curvature – convex, lesser curvature – concave
- rugae – longitudinal folds that allow distention
Small intestine
convoluted tube that runs from the pyloric sphincter of the stomach to the large intestine, 2.7 - 5 m. Longest part of alimentary canal: site of most enzymatic digestion and all nutrient absorption, duodenum, jejunum, and ileum
Duodenum
5% of total length of small intestine:
- shortest, widest, and most fixed portion
- mostly secondarily retroperitoneal
- a complex organ receiving digestive enzymes from the pancreas (via the main
pancreatic duct) and bile from the liver and gallbladder (via the bile duct)
Jejunum and Ileum
Jejunum - begins at duodenojejunal
junction, 40% of total length
Ileum - ends at ileocecal junction, 55% of total length
SI walls
circular folds (plicae circulares)
- transverse ridges of the
mucosa and submucosa
- villi – finger-like projections
Large intestine
Last major organ of alimentary
canal, absorbs water and electrolytes, cecum (vermiform appendix), colon: ascending, transverse, descending, sigmoid, rectum, and anal canal
LI features
- Teniae coli: 3 thickened bands of
longitudinal smooth muscle fibers - Haustra: sacculations or pouches of
the colon between the teniae - Omental appendices: small, fatty
appendices or projections of visceral
peritoneum - Caliber: much larger internal diameter
compared to small intestine
Anus
- Rectum: fixed terminal part of LI continuous with the sigmoid colon at S3 vertebral level.
- Anal canal: last subdivision of large
intestine: - internal anal sphincter (involuntary)
- external anal sphincter (voluntary)
- anal columns: rectal vessels
- pectinate line
Pectinate line
Marks the junction between gut tube and body wall.
* Structures above line are innervated by visceral motor and sensory fibers; veins drain into the portal VS
* Structures below the line are innervated by somatic motor and sensory fibers; veins drain into the caval VS
Liver
largest internal organ and gland in body, intraperitoneal, every substance absorbed by the alimentary canal (except lipids), 1st to liver, metabolic functions, storage of glycogen, bile secretion
External liver
right, left, caudate, quadrate
Porta hepatis: passage of the hepatic portal vein, hepatic artery, hepatic ducts, hepatic
nerve plexus, and lymphatics
Falciform ligament - binds the liver to
the anterior abdominal wall
External liver part 2
- Round ligament (ligamentum teres): extends from umbilicus to the liver, obliterated remnant of UV that carried O2 blood from the placenta to fetus.
- Ligamentum venosum: a cord remnant of the ductus venosus that shunted blood from the UV to the IVC, attached to the P aspect of liver fissure
Gallbladder
muscular sac occupies gallbladder fossa, stores and concentrates bile -> absorbs water and salts, expels bile into duodenum, Right and left hepatic ducts drain right
and left portal lobes of liver, unite to
form common hepatic duct joined by cystic duct on right side to form bile duct
Pancreas
accessory digestive organ, lies
retroperitoneally in C- shaped curvature of duodenum, main pancreatic duct joins bile duct from the gallbladder, both empty in duodenum
Mesentery
2x layer of peritoneum, extends from body wall to digestive organs, holds the organs in place, provides a route for circulatory vessels and nerves, length determines
motility of an organ
Mesenteries
Lesser omentum – runs from the liver stomach.
Greater omentum – links inferior surface of stomach to adjacent organs, enlarged and covers small and parts of LI, highly mobile, may form adhesions around inflamed organs
Omentum and ligament
Omentum – a 2x layer extension of peritoneum attaching stomach and first part of the duodenum to adjacent organs
Ligaments - two layers of peritoneum that connect 2 organs to each other or an
organ to the abdominal wall, may transmit neurovascular structures
Ligament types
- hepatoduodenal ligament
-hypogastric ligament - falciform ligament (liver to
anterior abdominal wall) - splenorenal ligament (spleen to
left kidney)
Gut tube divisions in yolk sac
- foregut- rise to the esophagus, stomach, pancreas, duodenum, liver, and bile ducts
- midgut: SI distal to the bile duct, cecum, appendix, ascending and most of transverse colon
- hindgut: remainder of the colon
Blood supply in oral cavity
branches of the external carotid artery
supply O2 blood to viscera, muscles and glands of OC, via branches such as the
lingual, facial, superior thyroid and maxillary
Arterial Supply of the Alimentary Tract
supply to the abdominal part of the alimentary tract, spleen, liver, gallbladder, and pancreas is derived from the abdominal aorta: celiac trunk, superior mesenteric artery (SMA), Inferior Mesenteric artery (IMA)
Venous drainage of AT
main channel of PVS is the hepatic PV, formed by the union of the superior mesenteric and splenic veins, PVS collects blood from abdominal part
Enteric nervous system
gut’s brain, continuation of ANS, in alimentary canal, within walls,
Enteric neurons
Within the wall of the alimentary canal, these form reflex arcs of sensory, interneuron and motor neurons that
control the muscular and secretory functions of the digestive tract organs
Enteric neuron locations
- Myenteric plexus is located in the SM (muscularis externa), this plexus controls peristalsis.
- Submucosal plexus is located in the submucosal layer, this plexus controls secretion of GI glands and the muscularis mucosae
Muscularis externa
SM of tubular organs, composed of 2
layers with muscle fibers running in opposite directions. This muscle powers peristalsis
Muscularis mucosae
thin layer of SM in mucosal layer, assist
with secretion by compressing glands (Goblet cells) and can assist movement across the surface of the mucosal epithelium
ENS Innervation
Vagus and Splanchnic nerves transmit afferent (sensory) signals to the CNS.
- Visceral motor fibers from the ANS (Postganglionic S, Pre/ Postganglionic PS) synapse on the enteric neurons
S inhibits digestive function
PS stimulates digestive function
