Abdomen PDF

lOMoARcPSD|44175252 AZYGOS VEIN - Venous blood from the thorax is drained by the azygos vein into the SVC - Drains both parietal and visceral components of the thorax, except for the heart - Drains the venous blood from the organs/components supplies by the descending aorta: thoracic walls,...

lOMoARcPSD|44175252 AZYGOS VEIN - Venous blood from the thorax is drained by the azygos vein into the SVC - Drains both parietal and visceral components of the thorax, except for the heart - Drains the venous blood from the organs/components supplies by the descending aorta: thoracic walls, pericardium, lungs, trachea, bronchi, oesophagus, diaphragm - The way venous blood drains into the azygos vein varies greatly between people - Azygos vein is positioned posteriorly against the vertebral column - The heart is positioned more anteriorly, therefore the azygos vein must arch anteriorly - It arches over the right lung root, and then drains into the SVC - Impression from the azygos vein is seen on the medial surface of the right lung GI TRACT - Abdomen = cavity between thorax (above) and pelvis (below) - Abdominal wall is mostly made of muscle and covering structures (not bone) - These structures attach to the thorax and pelvis ANTERIOR ABDOMINAL WALL Bony Framework - Consists of bones of the thorax (above) and pelvis (below) - Anterior abdominal wall structures attach to: o Inferior border of the thorax o Iliac crest o Anterior superior iliac spine (ASIS) — inferior and anterior to iliac crest o Pubic tubercle (lateral) o Pubic crest (medial)  lOMoARcPSD|44175252 Lining/Covering Structures 8 structures, listen from superior to deep: - (1) skin - (2) superficial fascia (fat) - (3, 4, 5) paired muscles o 3 flat layers, located laterally § External Oblique § § Internal Oblique § Transversus abdominus § Fibre direction varies to increase abdominal wall support o 2 vertical muscles, located medially - (6) transversalis fascia - (7) extra-peritoneal fascia - (8) peritoneum = serous membrane lining the abdominal wall (parietal peritoneum) and viscera (visceral peritoneum) Lateral Flat Muscles - 3 layers, paired - Fleshy laterally, replaced by aponeuroses medially - Aponeuroses allow the abdomen to expend - Aponeuroses from each side meet and interdigitate, forming the linear alba (raphe)  lOMoARcPSD|44175252 External Oblique (EO) muscles - Superficial layer - Fibre direction = inferomedial - Medial attachment = linear alba - Superior attachment = ribs (EO fibres overlap the costal margin) - Posterior attachment = thoracolumbar fascia with the posterior abdominal wall - Inferior attachment o Lateral part attaches to the iliac crest and ASIS o Central part is free o Medial part attaches to the pubic tubercle and pubic crest (fibrous split of the tendons) - Inguinal ligament o Formed by free, central part of the inferior border of the EO o Thickened as band curves under o Extends from ASIS to pubic tubercle Internal Oblique (IO) Muscles - Intermediate layer - Fibre direction = superomedial (perpendicular to EO) - Medial attachment = linear alba - Superior attachment = costal margin - Posterior attachment = thoracolumbar fascia - Inferior attachment = lowermost IO fibres arise from the lateral 2/3 of the inguinal ligament, arch up and then go down to insert on the pubic crest via a conjoint tendon  lOMoARcPSD|44175252 Transversus Abdominus (TA) Muscles - Deep layer - Fibre direction = transverse - Medial attachment = linear alba - Superior attachment = costal margin - Posterior attachment = thoracolumbar fascia - Inferior attachment = lowermost TA fibres arise from the lateral 1/3 of the inguinal ligament, arch up and then go down to insert onto the pubic crest via a conjoint tendon - Conjoint tendon = 2 structures (IO and TA) which insert via a common tendon - Deep to the TA is transversalis fascia Medial Vertical Muscles Rectus Abdominus - Located on either side of the linear alba - Principle vertical muscle supporting the anterior abdominal wall - Origin on pubis, insertion on ribcage (overlaps costal margin) - 3 tendinous intersections which make the muscle stronger (4 short muscles, not 1 long muscle) - Enclosed in rectus sheath o Formed by aponeuroses of EO, IO and TA which pass behind or infront of the rectus abdominus o EO aponeurosis = in front o IO aponeurosis = splits and passes in front and behind o TA aponeurosis = behind o Creates a fibrous compartment for rectus abdominus  lOMoARcPSD|44175252 Pyramidalis Muscles - Pyramid shaped - Small - Don t support the anterior abdominal wall TESTICULAR DESCENT - Develop high up in the posterior abdominal wall (in extra-peritoneal fat) - Has to enter the scrotum to be functional as spermatogenesis is inhibited at core body temperature (2- 3O lower is ideal) - To do this, must descend to the anterior abdominal wall and leave the abdomen - Testes in the posterior abdominal wall connect to the scrotum through the gubernaculum (fibrous cord, also present in females) - Testicular descent occurs ~7 months during gestation Inguinal Rings - To leave the abdomen from extra-peritoneal fat, it needs to create a hole in transversalis fascia and the EO aponeurosis - Deep inguinal ring = circular hole in transversalis fascia - Superficial inguinal ring = triangular split in EP aponeurosis (fibrous split at inferior attachment) - Path between deep and superficial inguinal rings is oblique  lOMoARcPSD|44175252 Inguinal Canal - Path the testes take to descend into the scrotum - Goes through transversalis fascia (deep inguinal ring), TA, IO and EO (superficial inguinal ring) layers - The inguinal canal is superior to the inguinal ligament - Boundaries: o Floor = inguinal ligament o Roof = arching IO and TA fibres o Anterior wall = EO aponeurosis and IO fibres (laterally) o Posterior wall = transversalis fascia and conjoint tendon (medially) - Once the inguinal canal emerges from the superficial inguinal ring, it is the spermatic cord - Females still have inguinal canals (less prominent) Inguinal Hernia - Inguinal canal is a communicating structure from the abdomen to the perineum - Increased abdominal pressure can lead to abdominal contents protruding through the abdominal wall at sites of weakness (=hernia) - Inguinal hernia = protrustion of abdominal contents into the inguinal canal Cryptorchidism - Undescended testes - Can be abdominal, inguinal or pre-scrotal - Needs to be surgically corrected before 18 months — 2 years - Can cause infertility - Increases risk of testicular cancer  lOMoARcPSD|44175252 POSTERIOR ABDOMINAL WALL - Consists of muscle (and lumbar vertebra) - Attach to bony thorax, pelvis and vertebrae o Superiorly attach to the 12th rib o Medially attach to lumbar vertebrae o Laterally attach to thoracolumbar fascia o Inferiorly attach to the iliac crest Psoas Major - Paired muscle (on either side of the lumbar vertebrae) - Longitudinally oriented - Arises from the lumbar vertebra body - Passes inferiorly and under the inguinal ligament - Inserts on the lesser trochanter of the femur - Psoas minor o Lines the surface of psoas major anteriorly o Smaller than psoas major o Not present in all people or on both sides Quadratus Lumborum - Lateral to psoas major - Paired muscle on either side of psoas major - Arises from the 12th rib and the tips of the lumbar vertebrae transverse processes - Inserts onto iliac crest - Fills the space between the 12th rib and the iliac crest Iliacus - Paired muscle - Fills the space in the iliacus fossa of the hipbone - Inferior to quadratus lumborum and lateral to psoas major  lOMoARcPSD|44175252 Thoracolumbar Fascia - Muscles of the anterior and posterior abdominal walls and back muscles are all enclosed in thoracolumbar fascia - Fascia of anterior and posterior abdominal walls meets lateral to quadratus lumborum - Posterior abdominal wall muscles end where anterior abdominal wall muscles start - Creates a complete muscular wall ABDOMINAL QUADRANTS - Median plane = vertically oriented, from xiphoid process to pubic symphysis - Transumbilical plane = horizontally oriented, crosses the umbilicus - Creates 4 quadrants: left upper, right upper, left lower, right lower - Used to describe positioning of abdominal viscera  lOMoARcPSD|44175252 PERITONEUM - Innermost layer of the abdominal walls - Parietal peritoneum = lines abdominal wall - Visceral peritoneum = lines viscera - Peritoneal cavity = potential space between parietal and visceral peritoneum - Intraperitoneal viscus = suspended in the abdominal cavity, completely lined with visceral peritoneum - Retroperitoneal viscus o Sits up against the posterior abdominal wall o Outside the abdominal cavity o Inner surface lined with parietal peritoneum o e.g. kidneys are up against the posterior abdominal wall and its anterior surface is lined with parietal peritoneum MESENTERY - Double fold of peritoneum - Pathway for nerves and vessels - Provides motility - Not all viscera in the abdomen have a mesentery o Alternating pattern of viscera with and without mesentery in the GI tract o Intraperitoneal viscera have a mesentery o Retroperitoneal viscera do not have a mesentery OESOPHAGUS - Begins at C6 from the pharynx - Descends down the midline - Passes through the diaphragm at T10 - Enters the stomach from the right side - Muscular tube with inner circular and outer longitudinal muscles Constrictions - Cervical constriction o Where the oesophagus begins o C6 o Anatomical sphincter - Thoracic constriction o Bifurcation of the trachea and aortic arch compress the oesophagus from the left side o T4/5 - Diaphragmatic constriction o Oesophagus passes through the diaphragm, which creates a functional sphincter o T10  lOMoARcPSD|44175252 Oesophagogastric Junction - Where oesophageal mucosa changes to stomach mucosa - Sudden change - Z-line STOMACH - Left upper quadrant - Dilated J shaped - Hollow viscus - Intraperitoneal - 2 openings: o Cardiac orifice = proximal, where oesophagus enters stomach o Pyloric orifice = distal, where the duodenum starts - 2 curvatures: o Lesser curvature (right side) o Greater curvature (left side) - 2 surfaces: anterior and posterior surfaces - 4 parts: o Cardia = region near cardiac orifice o Fundus = part above cardiac orifice, holds gas o Body = majority of the stomach o Pyloric part = distal narrowing § Pyloric antrum (wider) § Pyloric canal (narrower, more distal) - Pyloric sphincter/pylorus o Anatomical sphincter o Located at the end of the pyloric canal o Controls the amount of chyme entering the duodenum (assists with absorption) o Rugae = gastric folds/mucosa on the internal surface  lOMoARcPSD|44175252 SMALL INTESTINE - Hollow viscus - 3 parts: duodenum, jejunum, ileum - Function in digestion and absorption - Wall comprises 2 complete muscle coats (inner circular and outer longitudinal muscles) Duodenum - Short - Retroperitoneal - C shapes - Laterally is the right kidney, medially is the head of pancreas - 4 parts: o 1st part (duodenal cap) = immediately after the pylorus o 2nd part § Descending component § Between the right kidney and pancreas § Papilla on internal medial wall secrete pancreatic enzymes and bile into the duodenum § Major duodenal papilla = secretes products from the bile duct and main pancreatic duct § Minor duodenal papilla = superior to major, secretes products from the accessory pancreatic duct o 3rd part = horizontal, crosses midline o 4th part = hooks around and joins with the jejunum  lOMoARcPSD|44175252 Jejunum - large (proximal 40% of small intestine) - intraperitoneal - the mesentery attaches jejunum to abdominal wall - Left upper quadrant - Larger calibre, holding more gastric contents as more absorption occurs in the jejunum - Mucosal folds increase surface area - Thick walled - Highly vascularised - Less fat in the mesentery (vessels and nerves more visible) Ileum - Large (distal 60% of the small intestine) - Intraperitoneal - the mesentery connects ileum to abdominal wall - Right lower quadrant (changes during pregnancy) - Lower calibre, holds less gastric contents as less absorption occurs in the ileum - Less mucosal folds - Less vascularised - Less fat in the mesentery (vessels and nerves less visible) LARGE INTESTINE - Ileocaecal junction = where the ileum enters the large intestine - Ascending colon o Retroperitoneal o Large intestine begins to ascend - Transverse colon o Intraperitoneal o Begins at the hepatic/right colic flexure near the liver o Traverses the midline o Longest part - Descending colon o Retroperitoneal o Begins at splenic flexure/left colic flexure near the spleen o Descends - Sigmoid colon = bends inferiorly and medially (S shaped, intraperitoneal) - Sigmoid colon then becomes the rectum and anal canal  lOMoARcPSD|44175252 Large Intestine Wall - Complete layer of inner circular muscle - Outer longitudinal layer of muscles is incomplete and split into 3 bands (tenia coli) - Tenia coli follow the entire length of the large intestine, but don t completely cover it à gives baggy appearance (haustra) - Omental appendices = fatty tags along the tenia coli Caecum - Intraperitoneal - Blind pouch - Inferior to ileocaecal junction - Right lower quadrant Appendix - Intraperitoneal - Right lower quadrant - Inferior to ileocaecal junction - Base of appendix located where the 3 tenia coli bands meet - Position varies, but the base is always the same Rectum - Retrperitoneal - Tenia coli bands merge to form a complete outer layer of longitudinal muscles at the rectum - No tenia coli - No haustra - No omental appendices  lOMoARcPSD|44175252 LIVER - Right upper quadrant - Sits under the right dome of the diaphragm - Solid viscus - Intraperitoneal - Partially protected by thoracic cage - Function in bile production and nutrient metabolism Diaphragmatic Surface - Anterior and superior - Where the liver sits against the diaphragm - Smooth - Partially protected by ribcage - Covered by peritoneum Visceral Surface - Posterior and inferior - Interface between liver and other viscera - Concaved due to impression of adjacent structures - IVC and gall bladder located at this surface - Covered by peritoneum (except IVC and gall bladder)  lOMoARcPSD|44175252 Portal Hepatis - Hilum (holds vessels, nerves, lymphatics and ducts) - Portal triad = portal vein, hepatic artery, bile duct - Bile duct = carries bile from the liver to the duodenum - Hepatic artery = principle arterial supply to the liver - Portal vein = carries venous blood from the GI tract, contains nutrients for metabolism in the liver Heptatic Veins - Drains the venous blood from the liver - Not in the hilum - Runs through grooves - Drains directly into the IVC Lobes - Diaphragmatic surface: falciform ligament separated the liver into 2 anatomical lobes (larger right and smaller left lobes) - Visceral surface o Right and left anatomical lobes o Fissures and grooves have structures running in them: § Left sagittal fissure (ligaments run in) § Right sagittal fissure (IVC and gall bladder located in) o Between these fissures is the hilum, separating the liver into 2 more accessory lobes: § Caudate lobe (above hilum) § Quadrate lobe (below hilum) o Accessory lobes are actually in the right lobe  lOMoARcPSD|44175252 GALL BLADDER - Located at the visceral surface of the liver - Not covered in peritoneum - Hollow viscus - Right upper quadrant - 4 parts: o Fundus = blind end o Body o Neck = narrowing o Cystic duct - Function to store and concentrate bile (produced by the liver) - Overconcentration of bile à gall stones Bile Pathway - Bile goes from the liver, through hepatic ducts to the common hepatic duct - Common hepatic duct and cystic duct merge to form the common bile duct - Common bile duct enters the duodenum through the major duodenal papilla - Major duodenal papilla has a functional sphincter - Contraction (regulated by nerves) causes the sphincter to close, and causes bile to fill and collect in the gall bladder - Gall bladder contracts, pushing bile through the cystic and bile ducts into the duodenum PANCREAS - Left upper quadrant - Retroperitoneal - Solid viscus - 4 parts: o Head = surrounded by C shaped duodenum o Neck o Body o Tail = located against spleen - Exocrine and endocrine functions - Exocrine secretion into the duodenum: o Main pancreatic duct § Collects pancreatic enzymes from the tail, body, neck and head § Secretes into the duodenum via the major duodenal papilla  lOMoARcPSD|44175252 o Accessory pancreatic duct § Collects pancreatic enzymes from the head § Secretes into the duodenum via the minor duodenal papilla SPLEEN - Left upper quadrant - Solid viscus - Intraperitoneal - Associated with GI tract organs - Largest lymphatic organ - Rich blood supply - 2 surfaces: diaphragmatic and visceral surfaces - Hilum is located at the visceral surface (where splenic arteries/veins enter/exit the spleen) - Located against the diaphragm and ribs 9, 10 and 11 on the left side - Fracture of these ribs can cause damage to the spleen - Spleen is soft and highly vascularised with a delicate capsule - Sharp edges of fractured ribs can lacerate the capsule, causing profuse bleeding into the abdominal cavity ABDOMINAL AORTA - Abdominal organs are supplied by the abdominal aorta - Enters the abdomen at T12 - Bifurcates into the iliac arteries at L4  lOMoARcPSD|44175252 Anterior Surface 3 Unpaired Branches - Supply unpaired viscera (GI tube) - Celiac trunk = foregut (abdominal oesophagus to the major duodenal papilla) - Superior mesenteric artery = midgut (major duodenal papilla to distal 1/3 of the transverse colon) - Inferior mesenteric artery = hindgut (distal 1/3 of the transverse colon to ½ way through the anal canal) 3 Paired Branches - Supply paired viscera - Suprarenal arteries = adrenal glands - Renal arteries = kidneys - Testicular/ovarian arteries = gonads Posterior Surface - Paired arteries supply the abdominal wall structures - Phrenic arteries = diaphragm - Parietal arteries = anterior and posterior abdominal walls VENOUS DRAINAGE - All abdominal venous blood drains into the IVS - Venous blood from paired viscera and abdominal walls drains directly into the IVC - Venous blood from unpaired viscera (except the liver) drains into the IVC via the portal vein