Anatomy Flashcards
Retroperitoneal structures include GI structures that lack mesentery and non-GI structures.
Injuries to retroperitoneal structures –> blood gas accumulation in retroperitoneal space
Suprarenal (adrenal) glands
Aorta + IVC
Duodenum (2nd through 4th parts)
Pancreas (except tail)
Ureters
Colon (descending and ascending)
Kidneys
Esophagus (thoracic portion)
Rectum (partially)
Important gastrointestinal ligaments (6)
- Falciform
- Hepatoduodenal
- Gastrohepatic
- Gastrocolic
- Gastrosplenic
- Splenorenal
Falciform ligament
- Connects: liver to anterior abdominal wall
- Structures contained:
- Ligamentum teres hepatis (derivative of fetal umbilical vein)
- Notes:
- Derivative of ventral mesentery
Hepatoduodenal ligament
- Connects: liver to duodenum
- Structures contained:
- Portal triad - proper hepatic a., portal vein, common bile duct
- Notes:
- Pringle maneuver - ligament may be compressed between thumb and index finger (placed in omental foramen to control bleeding)
- Borders omental foramen (foramen of Winslow), which connects greater and lesser sacs
Gastrohepatic ligament
- Connects liver to lesser curvature of stomach
- Structures contained:
- Gastric arteries
- Notes:
- Separates greater and lesser sacs on the right
- May be cut during surgery to access lesser sac
Gastrocolic ligament
- Connects greater curvature and transverse colon
- Structures contained:
- Gastroepiploic arteries
- Notes:
- Part of greater omentum
Gastrosplenic ligament
- Connects: Greater curvature and spleen
- Contains:
- Short gastrics, left gastroepiploic vessels
- Notes:
- Separates greater and lesser sacs on the left
- Part of greater omentum
Splenorenal ligament
- Connects: Spleen to posterior abdominal wall
- Structures contained:
- Splenic artery and vein, tail of pancreas
Digestive Tract Anatomy
Layers of the gut (inside to outside - MSMS)
- Mucosa - epithelium, lamina propria, muscularis mucosa
- Submucosa - includes submucosal nerve plexus (Meissner), secretes fluid
- Muscularis externa - includes myenteric nerve plexus (Auerbach), motility (inner circular layer, outer longitudinal layer)
-
Serosa (when intraperitoneal), adventitia (when retroperitoneal)
- Vasculature
- Lymphatics
Ulcers can extend into submucosa, inner or outer muscular layer.
Erosions = mucosa only
Frequencies of basal electric rhythm (slow waves)
- Stomach - 3 waves/min
- Duodenum - 12 waves/min
- Ileum - 8-9 waves/min
Digestive Tract Histology
Esophagus
Stomach
- Esophagus:
- nonkeratinized stratified squamous epithelium
- Stomach:
- gastric glands
Digestive Tract Histology
Duodenum
Jejunum
Ileum
Colon
Duodenum:
- villi and microvilli increase absorptive surface
- brunner glands (HCO3- secreting cells of submucosa)
- crypts of Lieberkuhn
Jejunum
- plicae circulares
- crypts of lieberkuhn
Ileum
- Peyer patches (lymphoid aggregates in lamina propria, submucosa)
- Plicae circulares (proximal ileum)
- crypts of lieberkuhn
- Largest number of goblet cells in small intestine
Colon
- crypts of lieberkuhn but NO VILLI
- Abundant goblet cells
Abdominal aorta and branches
T12
L1
L2
L3
L4
L5
Arteries supplying GI structures branch anteriorly.
Arteries supplying non-GI structures branch laterally and posteriorly.
- T12: IVC (Right), Celiac trunk, Middle Suprarenal
- L1-L2: SMA, Renal, Gonadal (testicular/ovarian)
- L3: IMA
- L4: “BiFOURcation”
- L5: R & L common iliac (w/ R & L internal iliac coming off), median sacral artery
SMA (Wilkie’s) Syndrome
Intermittent intestinal obstruction symptoms (primarily postprandial pain) when transverse (third) portion of duodenum is compressed between SMA and aorta
Typically occurs in conditions associated with diminished mesenteric fat (e.g., low body weight/malnutrition)
GI Blood Supply and Innervation:
Foregut
Artery: Celiac trunk (L gastric, common hepatic, splenic)
PSNS: Vagus
SNS: T5-T11
Vertebral level: T12-L1
Structures supplied:
- Pharynx (vagus nerve only), lower esophagus (celiac artery only) to proximal duodenum
- Liver, gallbladder, pancreas, spleen (mesoderm)
GI Blood Supply and Innervation:
Midgut
Artery: SMA
PSNS: Vagus
SNS: T11-T12
Vertebral level: L1
Structures supplied:
- Distal duodenum to proximal 2/3 transverse colon
GI Blood Supply and Innervation:
Hindgut
Artery: IMA
PSNS: S2-S4
SNS: L1-L2
Vertebral level: L3
Structures supplied:
- Distal 1/3 transverse colon to upper portion of rectum
Celiac Trunk = main blood supply of stomach
Strong anastomoses exist between:
Common hepatic artery, L gastric a., splenic artery
Anastomoses:
L and R gastroepiploics
L and R gastrics
Portosystemic anastomoses (3)
Site of anastamosis:
Clinical Sign:
Portal <–> Systemic:
- Esophagus
- Esophageal varices
- Left gastric <–> azygos
- Umbilicus
- Caput medusae
- Paraumbilical <–> small epigastric veins of anterior abdominal wall
- Rectum
- Anorectal varices
- Superior rectal <–> middle and inferior rectal
Treatment for portal HTN
TIPS (transjugular intrahepatic portosystemic shunt) b/w portal vein and hepatic vein relieves portal HTN by shunting blood to systemic circulation, bypassing liver
Pectinate (dentate) line
Formed where endoderm (hindgut) meets ectoderm
Above pectinate line issues
Blood supply
Lymphatic drainage
Internal hemorrhoids, adenocarcinoma
**Internal hemorrhoids receive visceral innervation –> not painful
Arterial supply: superior rectal artery (branch of IMA)
Venous drainage: superior rectal vein –> inferior mesenteric vein –> portal system
Lymphatic drainage to internal iliac lymph nodes
Below pectinate line issues
Blood supply
Lymphatic drainage
External hemorrhoids, anal fissures, SCC
**External hemorrhoids receive somatic innervation (inferior rectal branch of pudendal n.) –> PAINFUL if thrombosed
Arterial supply: inferior rectal artery (branch of internal pudendal a.)
Venous drainage: inferior rectal vein –> internal pudendal vein –> internal iliac vein –> common iliac vein –> IVC
Lymphatic drainage to superficial inguinal nodes
Anal Fissure
Description:
Association:
Tear in anal mucosa below pectinate line
- Pain while pooping
- Blood on toilet Paper
- Located Posteriorly b/c area is Poorly Perfused
Associated with low-fiber diets and constipation
Liver tissue architecture
What does the apical surface of hepatocytes face?
What does the basolateral surface face?
Kupffer cells?
Hepatic stellate (Ito) cells?
Apical: Bile canaliculi
Basolateral: sinusoids
Kupffer cells (specialized macrophages) form lining of sinusoids
Hepatic stellate (Ito) cells in space of Disse store vitamin A (when quiescent) and produce ECM (when activated)
Zone I, II, III
Zone I - periportal zone
- Affected 1st by viral hepatitis
- Ingested toxins (e.g., cocaine)
Zone II - intermediate zone
- Yellow fever
Zone III - pericentral vein (centrilobular) zone
- Affected 1st by ischemia
- Contains cytochrome P-450 system
- Most sensitive to metabolic toxins
- Site of alcoholic hepatitis
Biliary Structures
Gallstones –> symptoms
Tumors that arise in head of pancreas (usually ductal adenocarcinoma) can cause what?
Gallstones (filling defects) that reach confluence of common bile duct and pancreatic ducts at ampulla of Vater can block both common bile and pancreatic ducts (double duct sign), causing both cholangitis and pancreatitis respectively.
Tumors that arise in head of pancreas –> obstruct common bile duct –> painless jaundice
Femoral region organization (lateral to medial)
Femoral triangle borders:
Femoral sheath:
Nerve-Artery-Vein-Lymphatics
Femoral triangle borders:
- Medial: adductor longus
- Lateral: Sartorius
- Superior: Inguinal ligament
Femoral sheath:
Fascial tube 3-4 cm below inguinal ligament (contains femoral vein, artery, and canal - deep inguinal lymph nodes…. but NOT femoral nerve)
Inguinal canal
Internal spermatic fascia (transversalis fascia)
Cremasteric muscle and fascia (Internal oblique)
External spermatic fascia (External oblique)
Hernias
Complicated hernia presentation
Protrusion of peritoneum through an opening, usually at a site of weakness
Contents at risk for incarceration (not reducible back into abdomen/pelvis) and strangulation (ischemia and necrosis)
Complicated hernia presentation: tenderness, erythema, fever
Diaphragmatic hernia
Most commonly a hiatal hernia (stomach herniates upward through esophageal hiatus of diaphragm) - 2 types
Abdominal structures enter thorax; may occur due to congenital defect of pleuroperitoneal membrane, or as a result of trauma
Commonly occurs on L side due to relative protection of right hemidiaphragm by liver
Sliding hiatal hernia: most common (GEJ displaced upward; “hourglass stomach”)
Paraesophageal hernia: GEJ normal –> fundus protrudes into thorax
Indirect inguinal hernia
Indirect Inguinal Hernia
Goes through internal (deep) inguinal ring, external (superficial inguinal ring), and into scrotum –> follows path of descent of testes… covered by all 3 layers of spermatic fascia
Enters internal inguinal ring LATERAL to inferior epigastric vessels
Occurs in infants owing to failure of processus vaginalis to close (can form hydrocele); much more common in males
What is the cause of indirect hernias?
Patent Processus Vaginalis
(allows communication b/w peritoneum and testes)
Direct Inguinal Hernia
Direct Inguinal Hernia
- Protrudes through inguinal (Hesselbach) triangle
- Inferior epigastric vessels
- Lateral border of rectus abdominis
- Inguinal ligament
- Bulges directly through abdominal wall medial to inferior epigastric vessels
- Goes through external (superficial) inguinal ring only
- Covered by external spermatic fascia
- Usually in elderly men (weak abdominal muscles - transversalis fascia)***
**MDs don’t LIe
Femoral hernia
Protrudes below inguinal ligament through femoral canal below and lateral to pubic tubercle
More common in females
More likely to present with incarceration or strangulation than inguinal hernias
The diaphragm is derived from four embryonic structures.
- Septum transversum
- Pleuroperitoneal membranes
- Mesoderm of body wall
- Mesoderm of esophagus
What is the most common type of hernia?
Bochdalek hernia
Occurs in posterolateral portion of diaphragm
Mesenteries divide coelomic cavity into R and L halves.
Upper abdomen:
Stomach and gut are suspended in the middle.
Liver is suspended in _______ mesentary.
Spleen is suspended in _______ mesentary.
Liver is suspended in ventral mesentary.
- Persists as hepatic ligaments and lesser omentum
- __Falciform ligament (remnant of ligamentum teres)
- Lesser omentum
- Hepatogastric
- Hepatoduodenal
Spleen is suspended in dorsal mesentary.
Dorsal Mesentary derivatives
Greater Omentum
- Gastrocolic
- Gastrosplenic
- Splenorenal
- Mesentery of small intestine
- Mesocolon
Anterior Abdominal Wall: Anatomy
above and below arcuate line
What is the surgical landmark for appendicitis?
Teniae coli
Begins as a continuous layer of longitudinal muscle that surrounds rectum just below serosa… at rectosigmoid jxn, this layer condenses to form 3 distinct longitudinal bands that travel on the outside of the entire colon before converging at the root of the appendix
