External Oblique Muscle
Location: Most superficial and largest of the flat abdominal muscles. Shape: Fibers run inferomedially (‘hands in pockets’). Function: Compresses abdomen; contralaterally rotates and bilaterally flexes the trunk.
Internal Oblique Muscle
Location: Deep to the external oblique. Shape: Fibers run superomedially (perpendicular to external oblique). Function: Compresses abdomen; ipsilaterally rotates and bilaterally flexes the trunk.
Transversus Abdominis Muscle
Location: Deepest of the three flat abdominal muscles. Shape: Fibers run horizontally (transversely). Function: Compresses abdominal contents; stabilizes the lumbar spine and pelvis (‘corset muscle’).
Rectus Abdominis Muscle
Location: Long, paired muscle running vertically along the anterior abdominal wall. Shape: ‘Six-pack’ muscle. Function: Flexes the lumbar spine and tenses the abdominal wall.
Tendinous Inscriptions (Intersections)
Location: Three or four fibrous bands that cross the rectus abdominis muscle horizontally. Shape: Horizontal lines segmenting the muscle. Function: Adhere the rectus abdominis to the anterior rectus sheath, creating the ‘six-pack’ appearance.
Anterior Rectus Sheath
Location: Fibrous compartment located anterior to the rectus abdominis muscle. Shape: Aponeurosis formed by the external oblique and a split layer of the internal oblique. Function: Encloses and protects the rectus abdominis muscle.
Posterior Rectus Sheath
Location: Fibrous compartment located posterior to the rectus abdominis muscle, primarily above the arcuate line. Shape: Aponeurosis formed by the transversus abdominis and a split layer of the internal oblique. Function: Encloses and protects the rectus abdominis muscle.
Arcuate Line
Location: Horizontal line on the inner surface of the anterior abdominal wall, about one-third of the way from the umbilicus to the pubic crest. Shape: A curved line marking a structural change. Function: Marks the point where the posterior rectus sheath ends, and the inferior epigastric vessels enter the rectus sheath.
Linea Alba
Location: Midline fibrous band running vertically from the xiphoid process to the pubic symphysis. Shape: A white line down the center of the abdomen. Function: Connects the left and right rectus sheaths, serving as an attachment point for abdominal muscles.
Inguinal Canal
Location: An oblique passage through the inferior part of the anterior abdominal wall. Shape: A 4 cm long canal running parallel to the inguinal ligament. Function: Allows passage of the spermatic cord (in males) or the round ligament of the uterus (in females) from the abdomen to the perineum.
Inguinal Ligament
Location: Extends from the anterior superior iliac spine (ASIS) to the pubic tubercle. Shape: A folded-under, inferior border of the external oblique aponeurosis. Function: Forms the floor of the inguinal canal and serves as a retinaculum for structures passing from the trunk to the lower limb.
Inguinal Rings (Superficial & Deep)
Location: The deep ring is an opening in the transversalis fascia; the superficial ring is an opening in the external oblique aponeurosis. Shape: Openings at either end of the inguinal canal. Function: Serve as the entrance (deep) and exit (superficial) of the inguinal canal.
Spermatic Cord (Round Ligament of Uterus)
Location: Passes through the inguinal canal. Shape: A bundle of structures including fascia, vessels, nerves, and the ductus deferens (male) or round ligament (female). Function: Suspends the testis in the scrotum and contains structures running to and from the testis.
Testes
Location: Paired oval organs located within the scrotum. Shape: Ovoid glands. Function: Produce sperm (spermatogenesis) and male sex hormones, primarily testosterone.
Scrotum
Location: A fibromuscular cutaneous sac located inferior to the penis. Shape: Pouch of skin and muscle. Function: Contains the testes, epididymis, and lower parts of the spermatic cord; regulates testicular temperature for optimal sperm production.
Ductus (Vas) Deferens
Location: A muscular tube that runs from the epididymis, through the spermatic cord and inguinal canal, to the ejaculatory duct. Shape: Long, cord-like tube. Function: Transports sperm from the epididymis to the ejaculatory ducts in anticipation of ejaculation.
Cremaster Muscle
Location: A thin layer of skeletal muscle found within the spermatic cord. Shape: Muscle fibers surrounding the cord. Function: Contracts to elevate the testes (cremasteric reflex), important for temperature regulation.
External Spermatic Fascia
Location: The outermost fascial layer covering the spermatic cord. Shape: Thin membranous layer. Function: A covering for the spermatic cord, derived from the aponeurosis of the external oblique muscle.
Iliohypogastric Nerve (L1)
Location: Arises from the L1 spinal nerve, runs across the quadratus lumborum, and pierces the transversus abdominis. Shape: A nerve branching from the lumbar plexus. Function: Provides motor innervation to the internal oblique and transversus abdominis, and sensory innervation to the skin of the suprapubic and gluteal regions.
Ilioinguinal Nerve (L1)
Location: Arises from the L1 spinal nerve, travels with the spermatic cord through the inguinal canal. Shape: A nerve that passes through the superficial inguinal ring. Function: Provides sensory innervation to the skin of the upper medial thigh, root of the penis and scrotum (male), or mons pubis and labia majora (female).
Inferior Epigastric Artery
Location: Arises from the external iliac artery and ascends on the deep surface of the anterior abdominal wall to enter the rectus sheath below the arcuate line. Shape: Artery running superiorly. Function: Supplies blood to the rectus abdominis muscle and the anterior abdominal wall.
Superior Epigastric Artery
Location: A terminal branch of the internal thoracic artery, it descends within the rectus sheath. Shape: Artery running inferiorly. Function: Supplies blood to the upper rectus abdominis muscle and anastomoses with the inferior epigastric artery.
Median Umbilical Fold
Location: A single fold in the midline extending from the apex of the bladder to the umbilicus. Shape: Midline peritoneal fold. Function: Covers the median umbilical ligament, which is a remnant of the fetal urachus.
Medial Umbilical Fold
Location: Paired folds lateral to the median umbilical fold. Shape: Paired peritoneal folds. Function: Covers the medial umbilical ligaments, which are remnants of the fetal umbilical arteries.
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Unit 129
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Arm37
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Unit 225
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Thorax, Chest Wall, Pleura and Lungs26
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Heart and Great Vessels46
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Abdominal Wall and Inguinal Region48
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Peritoneum and Abdominal Viscera47
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Diaphragm and Posterior Abdominal Wall34
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Pelvic Cavity39
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Pelvic Cavity and Viscera35
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Perineum1
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Bones and Fascia of the Lower Limb43
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Anterior and Medial Thigh40
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Gluteal Region23
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Posterior Thigh and Popliteal Fossa11
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Anterior and Lateral Leg and Foot24
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Posterior Leg and Foot31
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Joints of the Leg and Foot48
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Anterior and Medial Thigh Muscles of The Leg13
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Gluteal Region/Posterior Thigh Muscles13
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Posterior Leg Muscles7
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Anterior Leg and Dorsum of Foot and Lateral Leg Muscles8
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Plantar Foot Muscles10
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Back and Suboccipital Muscles25
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Vertebral Column26
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Anterior Neck Muscles and Nerves3
