Anatomy of the Abdomen I (University of the Western Cape) PDF

Anatomy of the Abdomen I Anterior Abdominal Wall University of the Western Cape  Abdomen Overview – Cylindrical chamber between inferior thoracic aperture & pelvic inlet – Enclosed by the abdominal wall & contains the peritoneal cavity Abdominal org...

Anatomy of the Abdomen I Anterior Abdominal Wall University of the Western Cape  Abdomen Overview – Cylindrical chamber between inferior thoracic aperture & pelvic inlet – Enclosed by the abdominal wall & contains the peritoneal cavity Abdominal organs are either suspended in the peritoneal cavity by mesentery (intraperitoneal) or positioned between cavity & musculoskeletal wall (retroperitoneal) – Contents: Major organs of the gastrointestinal tract, urinary system, suprarenal glands, major nerves & blood vessels – Functions: (1) houses & protects major viscera, (2) assists breathing, (3) changes in intra-abdominal pressure – coughing, sneezing & voiding – micturition, defecation & parturition 2  Abdominal Cavity General organization: a central tube (GIT) is suspended from the posterior abdominal wall and partly from the anterior wall. Abdominal Wall The abdominal wall consists partly of bone but mainly of muscle. Skeletal part: 5 lumbar vertebrae, costal margin, ribs XI & XII, pelvic bones. Muscular part: anterolateral wall & part of posterior abdominal wall. 3 Contents & Functions 4  Abdomen Surface Topography – Used to describe the location of abdominal organs & pain associated with abdominal problems 2 Schemes: I. 4 quadrants – horizontal transumbilical plane & vertical median plane II. 9 regions – 2 horizontal planes - transpyloric & intertubercular – 2 vertical planes – midclavicular planes (Lt & Rt) 5  Four-Quadrant Pattern Nine-Region Pattern Transpyloric plane Midclavicular planes Transumbilical plane Median plane Intertubercular plane It is customary to relate pains, swellings, or positions of organs to one of these regions e.g. an epigastric swelling; the appendix is in the hypogastric (pubic) region. 6  Abdomen Abdominal Wall – Covers a wide area, costal margin to pelvic bones – Layers (superficial to deep): i. Skin – shows ‘creases’, represent Langer’s lines ii. Superficial fascia: fatty layer – contains variable fat ♀>♂; membranous layer – fibrous tissue iii. Muscles: covers by deep fascia; support, protect, move trunk, maintain posture, increase intra- abdominal pressure iv. Extraperitoneal fascia: thin, transparent membrane v. Parietal peritoneum: innermost layer 7  Superficial Deep Skin External oblique Superficial Internal oblique fascia (fatty) Transversus abdominis Superficial fascia Extraperitoneal (membranous) fat Transversalis fascia Deep fascia Parietal 8 peritoneum  Anterior Abdominal Wall Anterolateral Muscles – 5 paired muscles in the anterolateral group: – 3 flat muscles, each originates posteriorly and inserts anteriorly along midline via an aponeurosis : I. External oblique II. Internal oblique III.Transversus abdominis – 2 vertical muscles, located near midline and enclosed in a tendinous sheath formed by the flat muscles: IV. Rectus abdominis V. Pyramidalis 9  External oblique muscle Origin: outer surfaces of the lower 8 ribs (ribs V-XII). Insertion: lateral lip of iliac crest, aponeurosis attached to linea alba. Innervation: lower 6 thoracic spinal nerves. Function: compress abdomen, flex and bend trunk, rotation. 10  Anterior superior iliac spine Pectineal ligament Inguinal ligament Pubic tubercle Lower border of external oblique is Lacunar ligament thickened and forms the inguinal ligament. The lacunar ligament and pectineal ligament are fibrous extensions at the medial end of the inguinal ligament. 11  Internal oblique muscle & aponeurosis Origin: thoracolumbar fascia, iliac crest, lateral 2/3 of inguinal ligament. Insertion: lower 4 ribs, linea alba, pubic crest and pectineal line. Innervation: lower 6 thoracic spinal nerves and L1. Function: compress abdomen, flex and bend trunk, rotation. 12 Internal oblique Transversus abdominis External oblique Thoracolumbar fascia 13 Transversus abdominis muscle & aponeurosis Origin: thoracolumbar fascia, iliac crest, lateral 1/3 of inguinal ligament, costal cartilages of lower 6 ribs. Insertion: linea alba, pubic crest and pectineal line. Innervation: lower 6 thoracic spinal nerves and L1. Function: compress abdomen. 14  “6-pack” Rectus abdominis muscle Origin: pubic crest, pubic tubercle and pubic symphysis. Insertion: costal cartilages of ribs V-VII, xiphoid process. Innervation: lower 6 thoracic spinal nerves. Function: compress abdomen, flex trunk and tense abdominal wall. 15 Pyramidalis muscle Origin: front of pubis and pubic symphysis. Insertion: linea alba. Innervation: T12 spinal nerve. Function: tense the linea alba. 16  Anterior Abdominal Wall Rectus sheath – The rectus abdominis and pyramidalis are enclosed in an aponeurotic sheath formed by a unique layering of the aponeuroses of the external and internal oblique and transversus abdominis – The rectus sheath completely encloses the upper ¾ of rectus abdominis, and covers only the anterior surface of the lower ¼ of the muscle Rectus sheath Rectus abdominis Rectus Arcuate line abdominis 17 Lateral View Anterior View  Anterior Abdominal Wall Rectus sheath (continued) – The rectus sheath has the following pattern: Above costal margin: anterior sheath comprises of the external oblique (EO) aponeurosis only Above arcuate line: aponeurosis of internal oblique (IO) splits to enclose the rectus abdominis; anteriorly it blends with aponeurosis of external oblique and posteriorly with that of transversus abdominis (TA) Below arcuate line: all 3 aponeuroses pass in front of the rectus abdominis; posteriorly the rectus abdominis is covered by transversalis fascia (TF) 18 19  Innervation The skin and muscles of the abdominal wall are supplied by T7-T12 and L1 spinal nerves. The anterior rami of these spinal nerves pass around the body in a plane between internal oblique and transversus abdominis. The spinal nerves enter the rectus sheath. Approaching the midline, the anterior cutaneous branches pass through the rectus abdominis muscle to supply the skin of the anterior wall. 20  Blood Supply The anterolateral abdominal wall is supplied by numerous blood vessels. These include branches of the (1) internal thoracic artery, (2) external iliac artery, and (3) femoral artery. Superior epigastric a. Inferior The superior epigastric artery epigastric a. (branch of internal thoracic a.) and the inferior epigastric artery (branch of external iliac a.) both enter the rectus sheath and anastomose. 21  Anterior Abdominal Wall Inguinal canal – A slit-like passage that extends in a downward and medial direction; 4cm long – Located above and parallel to the lower half of the inguinal ligament – It consists of: Deep (internal) ring Superficial (external) ring Anterior wall Posterior wall Roof Floor – Contents: spermatic cord in men round ligament in women 22 23  Roof Anterior Posterior wall wall Pubis bone Floor Lateral view Deep inguinal ring is lateral to the inferior epigastric vessels. 24  Contents The contents of the inguinal canal are the spermatic cord in men and the round ligament of the uterus in women. These structures enter the inguinal canal deep inguinal ring and exit the superficial inguinal ring. Spermatic cord Round ligament of uterus 25  Developing kidneys Peritoneum Mesonephric Gonads duct Testis Gubernaculum testis Gubernaculum testis 5 mm 2 months Colon Kidney 2 months The groin is a weak Epididymis area in the anterior Testis abdominal wall. Umbilical 3 months cord Penis 5 mm Epididymis Testis Urinary bladder 3 months 4 months Ureter Testicular artery and vein Vas deferens Superficial inguinal ring Pubis Epididymis Scrotal cavity (opened) lined Testis Testis by tunica Gubernaculum Scrotum 5 mm vaginalis testis 7 months Birth Sagittal sectional views of the Ureter Testicular artery positional changes involved and vein in the descent of the right Urinary bladder testis. Because the size of the Spermatic gubernaculum testis remains cord constant (see the scale bar at Scrotum (opened) the right) while the rest of the Birth fetus grows, the relative Frontal views showing the descent of position of the testis shifts. the testes and the formation of the 26 spermatic cords.  Anterior Abdominal Wall Inguinal Hernia – An inguinal hernia is a protrusion or passage of a peritoneal sac, with or without abdominal contents, through a weakened part of the abdominal wall in the groin – 2 types: indirect and direct – Indirect inguinal hernia Protruding sac enters inguinal canal by passing through deep inguinal ring, lateral to inferior epigastric vessels; most common type of inguinal hernia; more common in men than women; also called congenital inguinal hernia – Direct inguinal hernia A peritoneal sac enters the medial end of the inguinal canal directly through a weakened posterior wall; usually called an acquired inguinal hernia; commonly seen in elderly men. The bulging occurs medial to the inferior epigastric vessels 27 Indirect Direct 28  Indirect Inguinal Hernia Direct Inguinal Hernia Medial Lateral Medial Lateral Indirect: male Indirect: female Direct 29 Notes & Figures Adapted From: 1. Gray’s Anatomy For Students 2. Netter’s Atlas for Human Anatomy 3. Clinical Oriented Anatomy by Moore, Dalley & Agur 4. Instant Anatomy (http://www.instantanatomy.net/) 30