Gross Anatomy II - week 5 Lecture Notes.pdf

Regions of the Anterolateral Abdominal Wall symptoms and signs of abdominal diseases are located and recorded with reference to regions mapped out on anterolateral abdominal wall abdominal quadrants: anterolateral abdomina...

Regions of the Anterolateral Abdominal Wall symptoms and signs of abdominal diseases are located and recorded with reference to regions mapped out on anterolateral abdominal wall abdominal quadrants: anterolateral abdominal wall is divided into 4 quadrants (upper right, upper left, lower right and lower left quadrants) by a vertical plane and a horizontal plane that intersect at umbilicus vertical and horizontal planes: subcostal plane à horizontal plane that connects lowest points of right and left costal margins (10th costal cartilages) lies at the level of body of L3, near its upper border transtubercular plane- horizontal plane connecting tubercles of right and left iliac crests (lies at the level of body of L5, near its upper border midclavicular plane- vertical plane that passes through midpoint of clavicle and intersects halfway a line connecting anterior superior iliac spine (ASIS) to pubic tubercle 2 midclavicular planes and 2 horizontal planes (subcostal and transtubercular) are used to divide anterolateral abdominal wall into 9 regions: upper part (above subcostal plane): consists of epigastric region or epigastrium (center) and right and left hypochondriac regions middle part (between subcostal and transtubercular planes): consists of umbilical region (center) and right and left lateral regions (lumbar regions or flanks) lower part (below transtubercular plane): consists of pubic, hypogastric region or hypogastrium (center) and right and left inguinal (iliac) regions https://sites.google.com/view/grossanatomyii/week-5-lecture-notes 6/21/24, 1 34 PM Page 3 of 38 :  https://sites.google.com/view/grossanatomyii/week-5-lecture-notes 6/21/24, 1 34 PM Page 4 of 38 :  Layers of the Anterolateral Abdominal Wall (Superficial to Deep) skin superficial fascia muscles with their deep (investing) fasciae transversalis fascia extraperitoneal fascia parietal peritoneum Superficial Fascia divided into 2 layers in lower part of anterior abdominal wall: superficial, fatty layer (Camper’s fascia): continuous with superficial fat over rest of body and may be extremely thick deep, membranous layer (Scarpa’s fascia): on each side, it fuses with fascia lata (deep fascia of thigh) about a fingerbreadth below inguinal ligament and in the midline, it is continuous with superficial fascia of penis (or clitoris), dartos tunic/fascia (scrotum) and superficial perineal fascia (Colles’ fascia) https://sites.google.com/view/grossanatomyii/week-5-lecture-notes 6/21/24, 1 34 PM Page 5 of 38 :  Abdominal Muscles Transversalis Fascia superficial and deep surfaces of flat abdominal muscles are covered by deep (investing) fascia. These fascial layers are unremarkable, except for fascia that covers deep surface of transversus abdominis (transversalis fascia), which is better developed transversalis fascia is part of continuous layer of fascia (endoabdominal fascia) that lines inner surface of abdominal walls à name of fascia changes depending on region or muscle it covers (diaphragmatic fascia, transversalis fascia, iliacus fascia, etc.) Extraperitoneal Fascia layer of loose connective tissue, with a variable amount of fat, located between transversalis fascia and parietal peritoneum Parietal Peritoneum serous membrane that lines inner surface of anterolateral abdominal wall https://sites.google.com/view/grossanatomyii/week-5-lecture-notes 6/21/24, 1 34 PM Page 7 of 38 :  Muscles of the Anterolateral Abdominal Wall 3 broad and thin (flat) muscles on each side: external oblique, internal oblique and transversus abdominis on each side of anterior midline there is a long, vertical muscle (rectus abdominis) there is usually a small muscle anterior to lower part of rectus abdominis called pyramidalis (absent in about 20% of people) 3 flat abdominal muscles are muscular (fleshy) posterolaterally and aponeurotic (fibrous) anteromedially aponeuroses of 3 flat muscles pass medially and enclose rectus abdominis (and pyramidalis, if present) to form rectus sheath in midline of anterior abdominal wall, aponeuroses of 3 right flat muscles join aponeuroses of 3 left flat muscles à form fibrous band (linea alba) that extends from xiphoid process to pubic symphysis External Oblique Origin: outer surface of lower 8 ribs Insertion: on an anterior view, fibers run inferiorly and medially (similar to external intercostals). The lower fibers insert into iliac crest any remaining fibers become continuous with an aponeurosis which inserts into xiphoid process, linea alba and pubic bone inguinal (Poupart’s) ligament: lower border of external oblique aponeurosis that extends from ASIS to pubic tubercle and it is folded backward on itself forming the inguinal ligament (forms boundary between abdomen and thigh) superficial inguinal ring- opening in external oblique aponeurosis located immediately superior to pubic tubercle. It is the anterior (superficial) opening of inguinal canal https://sites.google.com/view/grossanatomyii/week-5-lecture-notes 6/21/24, 1 34 PM Page 8 of 38 :  Insertion: on an anterior view, upper fibers run superiorly and medially (similar to internal and innermost intercostals) while lower fibers are more horizontal, upper fibers insert into inferior border of lower 3 or 4 ribs and their costal cartilages à remaining fibers become continuous with an aponeurosis which inserts into xiphoid process, linea alba and pubic bone has a lower free border that arches over contents of inguinal canal Transversus Abdominis lies deep to internal oblique Origin: deep surface of lower 6 costal cartilages, thoracolumbar fascia, iliac crest and lateral ⅓ of inguinal ligament Insertion: fibers run horizontally forward à become continuous with an aponeurosis which inserts into xiphoid process, linea alba and pubic bone has a lower free border that arches over contents of inguinal canal Rectus Abdominis long strap muscle that extends along whole length of anterior abdominal wall à narrower and thicker below, broader and thinner above à it is separated from its fellow by linea alba Origin: pubic symphysis and pubic crest Insertion: 5th, 6th and 7th costal cartilages and xiphoid process divided into segments by 3 transverse fibrous bands (tendinous intersections or inscriptions) à superior tendinous intersection is just inferior to xiphoid process, inferior one is at the level of umbilicus, middle one is half-way between the other two Pyramidalis small triangular muscle located anterior to lower part of rectus abdominis, within rectus sheath may be absent on one or both sides Origin: anterior surface of body of pubis Insertion: linea alba Action: tensor of linea alba Actions of the Anterolateral Abdominal Muscles their tone plays an important role is supporting and protecting abdominal organs oblique muscles are involved in flexion, lateral flexion and rotation of trunk https://sites.google.com/view/grossanatomyii/week-5-lecture-notes 6/21/24, 1 34 PM Page 10 of 38 :  rectus abdominis flexes trunk transversus abdominis contributes little to trunk movements by contracting simultaneously with diaphragm, with glottis of larynx closed, anterolateral abdominal muscles increase intra-abdominal pressure à help with evacuation of contents of abdominal and pelvic hollow organs (micturition, defecation, vomiting, childbirth) assist in forced expiration (coughing and sneezing) by pulling down ribs and sternum Rectus Sheath (Netter’s Plate 253) formed by aponeurosis of 3 flat abdominal muscles contents: rectus abdominis pyramidalis (if present) terminal parts of lower 5 (7th to 11th) intercostal nerves and subcostal nerve superior and inferior epigastric vessels upper ¾ of anterior abdominal wall- aponeurosis of internal oblique splits into 2 laminae. The anterior lamina joins aponeurosis of external oblique to form anterior wall of rectus sheath and the posterior lamina joins aponeurosis of transversus abdominis to form posterior wall of rectus sheath lower ¼ of anterior abdominal wall-3 aponeuroses pass anterior to rectus abdominis muscle to form anterior wall of sheath. There is no posterior aponeurotic wall. At this level, rectus abdominis muscle is directly related posteriorly to transversalis fascia arcuate line is a curved line that marks lower end of posterior aponeurotic wall of rectus sheath. It is located half-way between umbilicus and pubic symphysis. Inferior to arcuate line, posterior aponeurotic wall of rectus sheath is lacking (aponeurosis of 3 flat abdominal muscles pass anterior to rectus muscle) posterior wall of sheath is not attached to rectus abdominis muscle, but the anterior wall of sheath is firmly attached to tendinous intersections of rectus abdominis muscle https://sites.google.com/view/grossanatomyii/week-5-lecture-notes 6/21/24, 1 34 PM Page 11 of 38 :  Nerves of the Anterolateral Abdominal Wall ventral rami of T7 to T11 spinal nerves (7th to 11th intercostal nerves) ventral ramus of T12 spinal nerve (subcostal nerve) ventral ramus of L1 spinal nerve (iliohypogastric and ilioinguinal nerves) for a large part of their course, these nerves run forward between internal oblique and transversus abdominis 7th to 11th intercostal nerves and subcostal nerve enter rectus sheath and supply rectus abdominis; iliohypogastric and ilioinguinal nerves do not enter rectus sheath nerves of anterolateral abdominal wall provide sensory innervation to skin and parietal peritoneum that line the outer and inner surfaces, respectively, of anterolateral abdominal wall and provide motor innervation to muscles of anterolateral abdominal wall Dermatomes of the Anterolateral Abdominal Wall T7 - just inferior to tip of xiphoid process T10 -level of umbilicus L1 -pubic symphysis and area immediately superior to it https://sites.google.com/view/grossanatomyii/week-5-lecture-notes 6/21/24, 1 34 PM Page 12 of 38 :  arteries of the anterior abdominal wall Arteries of the Anterolateral Abdominal Wall superior epigastric artery- terminal branch of internal thoracic artery (descends posterior to rectus abdominis within rectus sheath and supplies upper central part of anterior abdominal wall. It anastomoses with inferior epigastric artery) inferior epigastric artery- originates from distal part of external iliac artery (just above inguinal ligament) (runs superiorly and medially and enters rectus sheath and ascends posterior to rectus abdominis. It supplies lower central part of anterior abdominal wall. It anastomoses with superior epigastric artery deep circumflex iliac artery -originates from distal part of external iliac artery (just above inguinal ligament) and runs superiorly and laterally toward ASIS. It supplies lower lateral part of anterior abdominal wall 10th and 11th posterior intercostal arteries, subcostal artery and lumbar arteries (they supply lateral part of anterior abdominal wall) superficial epigastric and superficial circumflex iliac arteries (branches of femoral artery) - supply superficial structures of lower part of anterior abdominal wall https://sites.google.com/view/grossanatomyii/week-5-lecture-notes 6/21/24, 1 34 PM Page 15 of 38 :  Veins of the Anterolateral Abdominal Wall (netter’s plate 259) superficial veins: form a network that radiates out from umbilicus --- network drains superiorly into axillary vein and inferiorly into femoral vein and may provide collateral circulation during blockage of either vena cava deep veins (accompany corresponding arteries): superior epigastric vein- drains into internal thoracic vein inferior epigastric and deep circumflex iliac veins- drain into external iliac vein lower posterior intercostal and subcostal veins- drain into azygos (right) or hemiazygos (left) veins lumbar veins- drain into inferior vena cava Lymphatic Drainage of the Anterior Abdominal Wall superficial lymph vessels: above level of umbilicus lymph drains upward toward anterior axillary lymph nodes below level of umbilicus lymph drains downward toward superficial inguinal lymph nodes deep lymph vessels: follow arteries and deep veins and drain into internal thoracic (parasternal), external iliac, posterior mediastinal and lumbar (para-aortic) lymph nodes https://sites.google.com/view/grossanatomyii/week-5-lecture-notes 6/21/24, 1 34 PM Page 16 of 38 :  Inguinal Canal oblique passage, about 4 cm in length, through lower part of anterior abdominal wall lies parallel and immediately above medial part of inguinal ligament contents: males-spermatic cord (formed by structures running between testis and abdominopelvic cavity) and ilioinguinal nerve females- round ligament of uterus (fibrous cord that extends from uterus to labium majus), genital branch of genitofemoral nerve and ilioinguinal nerve in males, genital branch of genitofemoral nerve is part of spermatic cord openings: deep inguinal ring (opening in transversalis fascia) located approximately halfway between ASIS and pubic tubercle (inferior epigastric vessels pass medial to deep inguinal ring) superficial inguinal ring (opening in aponeurosis of external oblique) located immediately superior to pubic tubercle walls: (Netter’s Plate 263) anterior: aponeurosis of external oblique posterior: transversalis fascia inferior: inguinal ligament superior: lower borders of internal oblique and transversus abdominis https://sites.google.com/view/grossanatomyii/week-5-lecture-notes 6/21/24, 1 34 PM Page 18 of 38 :  Abdominal Hernia protrusion of abdominal contents beyond normal confines of abdominal wall - has 3 parts: hernial sac, contents of sac and coverings of sac sac: pouch (diverticulum) of parietal peritoneum contents: may consist of any structure found within abdominal cavity (piece of omentum, loop of small intestine, etc.) coverings: formed by layers of abdominal wall through which hernial sac passes there are various types of abdominal hernias (inguinal, femoral, umbilical, incisional, etc.) approximately 75% of abdominal hernias occur in inguinal region (most common type of abdominal hernia) inguinal hernias occur more often in males than females Types of Inguinal Hernias https://sites.google.com/view/grossanatomyii/week-5-lecture-notes 6/21/24, 1 34 PM Page 20 of 38 :  Indirect Inguinal Hernia most common type of inguinal hernia (⅔ to ¾ inguinal hernias are indirect) hernial sac leaves abdominal cavity lateral to inferior epigastric vessels, through deep inguinal ring à neck of hernial sac is narrow results from a persistent processus vaginalis (outpouching of peritoneum that in the fetus is responsible for formation of inguinal canal) à considered to be congenital in origin more common in children and young adults https://sites.google.com/view/grossanatomyii/week-5-lecture-notes 6/21/24, 1 34 PM Page 21 of 38 :  Direct Inguinal Hernia hernial sac leaves abdominal cavity medial to inferior epigastric vessels hernial sac protrudes through an area of relative weakness in posterior wall of inguinal canal inguinal (Hesselbach’s) triangle is bounded by inferior epigastric vessels (laterally), rectus abdominis (medially) and inguinal ligament (inferiorly). the neck of hernia sac is wide https://sites.google.com/view/grossanatomyii/week-5-lecture-notes 6/21/24, 1 34 PM Page 22 of 38 :  Intraperitoneal and Retroperitoneal Relationships terms used to describe relationship of abdominal organs to their peritoneal coverings intraperitoneal organ -organ that is almost totally covered with peritoneum ( ex.: stomach, jejunum, ileum, transverse colon, sigmoid colon, spleen) retroperitoneal organ- organ that is located posterior to peritoneal sac (between peritoneal sac and posterior abdominal wall) organ is only covered with peritoneum anteriorly (ex.: most of duodenum and pancreas, ascending colon, descending colon, kidneys, suprarenal glands, abdominal aorta, IVC) Peritoneal Folds ligament: two-layered peritoneal fold that connects an organ (usually a solid organ) to abdominal wall or another organ- does not consist of dense fibrous connective tissue like ligaments associated with joints some examples: Falciform ligament- peritoneal fold that connects liver to anterior abdominal wall (above umbilicus) coronary ligament- peritoneal fold that connects liver to diaphragm splenorenal ligament -peritoneal fold that connects spleen to left kidney -gastrosplenic ligament- peritoneal fold that connects spleen to stomach https://sites.google.com/view/grossanatomyii/week-5-lecture-notes 6/21/24, 1 34 PM Page 25 of 38 :  omentum: peritoneal fold that passes from stomach and proximal part of duodenum to another organ lesser omentum- two-layered peritoneal fold that connects lesser curvature of stomach and 1st part of duodenum to visceral (inferior) surface of liver has 2 parts: hepatogastric and hepatoduodenal ligaments hepatogastric ligament is thin hepatoduodenal ligament forms right margin of lesser omentum and is thick because it contains ducts, blood vessels, lymph vessels and nerves traveling to and from liver greater omentum- hangs down from greater curvature of stomach, like an “apron”, in front of loops of jejunum and ileum. It contains a variable amount of fat and consists of 4 peritoneal layers (2 anterior layers descend from greater curvature of stomach, fold back on themselves and ascend (becoming 2 posterior layers) to attach to transverse colon. The space between 2 anterior and 2 posterior layers is obliterated. Key relationship: The greater omentum attaches the stomach to the transverse colon. The transverse mesocolon attaches the transverse colon to the posterior abdominal wall. https://sites.google.com/view/grossanatomyii/week-5-lecture-notes 6/21/24, 1 34 PM Page 28 of 38 :  mesentery: two-layered peritoneal fold that connects intestines to posterior abdominal wall that allows blood vessels, lymph vessels and nerves to reach intestines from posterior abdominal wall parts of intestines that have mesentery are more mobile and are intraperitoneal. examples: mesentery of small intestine (or just simply “the mesentery”) à connects loops of jejunum and ileum to posterior abdominal wall transverse mesocolon (mesentery of transverse colon) à connects transverse colon to posterior abdominal wall sigmoid mesocolon (mesentery of sigmoid colon) à connects sigmoid colon to posterior abdominal and pelvic walls mesenteries have a root posterior border of mesentery attached to posterior abdominal wall https://sites.google.com/view/grossanatomyii/week-5-lecture-notes 6/21/24, 1 34 PM Page 30 of 38 :  Secondary Retroperitoneal Organs early in development, all parts of digestive tract are intraperitoneal and have a mesentery with further development, some parts of digestive tract adhere to posterior abdominal wall, loose their mesentery and become retroperitoneal (more fixed in position) à they are known as secondary retroperitoneal organs (ex. most of duodenum, most of pancreas, ascending colon, descending colon) Lesser Sac (Omental Bursa) part of peritoneal cavity located posterior to lesser omentum and stomach (all remaining peritoneal cavity is referred to as “greater sac”) superior recess: upward extension of lesser sac, located between liver and diaphragm inferior recess: downward extension of lesser sac between 2 anterior and 2 posterior layers of greater omentum (usually very short due to adherence of anterior and posterior layers of greater omentum) on the left it is closed by spleen, gastrosplenic ligament and splenorenal ligament on the right it communicates with greater sac via omental (epiploic) foramen (a.k.a. opening of lesser sac, foramen of Winslow) Epiploic (Omental) Foramen (Opening of Lesser Sac, Foramen of Winslow) boundaries: anteriorly: right, free border of lesser omentum (hepatoduodenal ligament), within which are structures traveling to and from liver (3 main structures: portal vein, proper hepatic artery and common bile duct) posteriorly: inferior vena cava superiorly: caudate lobe of liver inferiorly: 1st part of duodenum https://sites.google.com/view/grossanatomyii/week-5-lecture-notes 6/21/24, 1 34 PM Page 32 of 38 :  Peritoneal Folds in the Lower Part of the Anterior Abdominal Wall 1 median umbilical fold-formed by peritoneum that covers median umbilical ligament (fibrous cord that extends from apex of urinary bladder to umbilicus) à it is a remnant of allantois of embryo (when lumen of allantois obliterates in the embryo, it is called urachus; in the adult it is known as median umbilical ligament) 2 medial umbilical folds (1 on each side) - formed by peritoneum that covers medial umbilical ligaments à fibrous cords that represent distal, obliterated parts of umbilical arteries 2 lateral umbilical folds (1 on each side) -formed by peritoneum that covers inferior epigastric vessels https://sites.google.com/view/grossanatomyii/week-5-lecture-notes 6/21/24, 1 34 PM Page 34 of 38 :  Other Subdivisions of the Abdominal Cavity transverse colon and its mesentery (transverse mesocolon) divide abdominal cavity into supracolic and infracolic compartments supracolic compartment: located above transverse colon and its mesentery- contains stomach, liver, gallbladder, spleen infracolic compartment:l ocated below transverse colon and its mesentery - contains most of the small and large intestines à divided into right and left infracolic spaces by mesentery of small intestine there is free communication between supracolic and infracolic compartments via paracolic gutters (grooves between lateral aspects of ascending and descending colon and abdominal wall) https://sites.google.com/view/grossanatomyii/week-5-lecture-notes 6/21/24, 1 34 PM Page 36 of 38 :  Nerve Supply of the Peritoneum parietal peritoneum: peritoneum that covers central part of undersurface of diaphragm is innervated by phrenic nerves (pain referred to shoulder) peritoneum that covers peripheral part of undersurface of diaphragm is innervated by lower 5 intercostal nerves and subcostal nerve remaining of parietal peritoneum is innervated by lower 5 intercostal nerves, subcostal nerve and iliohypogastric and ilioinguinal nerves visceral peritoneum is innervated by visceral sensory fibers that travel with sympathetic and parasympathetic fibers that supply organs pain originating from parietal peritoneum is usually more intense and well localized pain originating from visceral peritoneum is usually dull and poorly localized (referred pain) https://sites.google.com/view/grossanatomyii/week-5-lecture-notes 6/21/24, 1 34 PM Page 38 of 38 :