Anatomy of Abdomen- GI tract

Adonye Banigo & Abigail Vooght, Oct 2010

Plan- Lecture 1 Abdo Wall

Surface markings Regions Layers Inguinal canal & hernias Incisions

Abdo cavity Whistlestop tour of GI tract Viscera + peritoneum + embryology Peritoneal cavity

Surface markings Abdominal wall

surgical incisions Inguinal canal

hernias Whistle stop tour of gut (mouth > anus) incl. landmarks Embryology of gut

Foregut/ midgut/ hindgut principles

Peritoneum and mesenteries

Referred pain

Plan- Lecture 2

Key features of each organ The GI adnexae- liver, gallbladder, pancreas,

spleen Not including the bony pelvis, genitourinary

system, or histology of the gut

The Abdominal Wall

Role of Abdo Wall

• Moving the trunk• Depressing the ribs• Compressing the abdomen• Supporting and protecting organs

Surface Markings

Linea Alba

Linea semilunaris

Tendinous intersections (3)

Landmarks

Xiphisternum T9

Iliac crest

Costal Margin

Umbilicus L3/4

Midclavicular line

9 regions

Midclavicular line

Transpyloric plane (L1)

Transtubercular plane (L4/5)

9 regions

Umbilical

Suprapubic

Epigastric

9 regions

Lumbar

Iliac Fossae

Hypochondrium

9 regions

Layers of Abdo Wall- Laterally

Skin Superficial fascia

Camper’s (soft & spongy fat!) Scarpa’s (membranous)

External Oblique (Aponeurosis) Internal Oblique Transversus Abdominis Transversalis Fascia Extraperitoneal fat Peritoneum

Layers of Abdo Wall- Medially

Skin Superficial fascia

Camper’s (soft & spongy fat!) Scarpa’s (membranous)

Rectus Abdominis and Rectus Sheath Transversalis Fascia Extraperitoneal fat Peritoneum

Abdo wall- Layers Medially

Arcuate line (of Douglas)

Costal Margin

Inguinal canal

Passage for spermatic cord ♀// round ligament ♂ 4cm long Deep (internal) ring to superficial (external) ring Boundaries:

Anteriorly- E-O aponeurosis + I-O lateral 1/3 Posteriorly- transversalis fascia + conjoint tendon medially Above- arching fibres of internal oblique + transversalis Below- inguinal ligament (infolded gutter of E-O)

1) External oblique aponeurosis, 2) Internal oblique muscle, 3) Transversus abdominis muscle, 4) Endo abdominal fascia, 5) Internal inguinal ring, 6) Iliopubic tract, 7) Inguinal ligament, 8) Pubic symphisis, 9) Spermatic cord, 10) Interparietal connective tissue (cremasteric fascia), 11) cremasteric muscle, 12) Aponeurotic layer of posterior inguinal wall, 13) Fascial layer of posterior inguinal wall

Extenal Oblique Aponeurosis

Transversalis fascia

AS

IS

Pu

bic

Tu

bercle

Posterior

Anterior

Inguinal Canal- conceptual- from above

Conjoint Tendon

Internal Oblique

Deep and Superficial Rings

Deep Ring: Transversalis fascia evagination into canal as

internal spermatic fascia ½ inch above midpoint of inguinal ligament Transmits spermatic cord or round ligament

Superficial Ring: V-shaped defect in E-O aponeurosis Transmits spermatic cord + ilioinguinal nerve

Spermatic Cord: 3 coverings,6 constituents Coverings

External spermatic Fascia (from E-O apo) Cremastic muscle + fascia (?I-O, TA) Internal spermatic Fascia (transversalis fascia)

Constituents Ductus Deferens Arteries: Testicular artery, artery to ductus Veins: Pampiniform plexus Lymphatics Nerves: Genital br of genitofemoral n + sympathetic twigs Processus Vaginalis

Indirect Inguinal Hernia

• Generally congenital• Lax deep ring• Repair by excising hernia sac and mesh to

reinforce ring

Direct Inguinal Hernia

• Generally weakness in EO aponeurosis• Repair by reinforcing external ring, suturing

mesh to conjoint tendon

PRINCIPLES OF INCISIONS• Adequate exposure of the organ• Follow cleavage lines in skin

(Langer’s lines)• Avoid neurovascular structures• Consider direction of muscles

fibres and location of aponeuroses

Abdo wall nerve supply

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9

101112-s/cL1-i/hL1-i/i

Abdo Wall Arterial Supply

Principles of Abdominal Incisions Adequate exposure of the organ Follow cleavage lines in skin (Langer’s lines) Avoid neurovascular structures Consider direction of muscle fibres and

location of aponeurosis

Midline

Paramedian

Pfannenstiel

Subcostal (Kochers)

Gridiron

Muscle split

Abdominal Incisions- access vs healing

The Abdominal Cavity

Viscera + peritoneum

Peritoneal Cavity

Viscera

• Urinary- kidneys, ureters• Endocrine- adrenal glands

Develop on post. Abdo wall (1° retroperitoneal)

Arterial supply from corresponding side of aorta

Nerve supply bilateral, true to level of origin

Referred pain to corresponding side

Digestive- GI tract, liver & biliary tract, pancreas

Haemopoietic- Spleen Develop on a mesentery

(which some lose to become 2° retroperitoneal)

Arterial supply from front of aorta

Nerve supply bilateral Referred pain to midline

Paired Unpaired

Intro: the Peritoneum

Serous membrane (latin =thin skin) 2 layers- visceral + parietal Parietal

Lines interior of body wall Nerve & vascular supply from body wall (somatic)

Visceral Covers viscera (!) Visceral supply

Mesenteries

Double layer of serous membrane (peritoneum), suspends all intraperitoneal viscera

Intermediary structure between parietal and visceral peritoneum

Function Provide mobile attachment for viscus Contains supply lines (sandwiched between 3

layers) All unpaired viscera develop on a mesentery

Whistlestop tour of gut

Stomach

Duodenum

Jejenum

Ileum

Caecum

Large Bowel

Rectum & Anus

Embryology of gut- 6/40

Midgut

Foregut

Hindgut

Posterior abdo wall

Mesentery (ventral)

Mesentery (dorsal)

Foregut Oropharynx to D2 (precisely opening of bile duct) Includes

Outgrowths: biliary tract Glands: liver & pancreas Spleen

Artery: Coeliac Nerve supply: T6- T9 spinal segments Rotation (on vertical axis of gut)- 90º left

Spleen from posterior (dorsal mesogastrium) to left Liver from anterior (ventral mesogastrium) to right

Retroperitoneal: 2nd part duodenum, spleen, most of pancreas

Rotation of foregut

Midgut

Foregut

Hindgut

Mesentery (ventral)

Mesentery (dorsal)

liver

Sp

leen

Foregut rotation 2

Greater sac

Lesser sac

Midgut

D2 to mid-transverse colon Artery: SMA Nerve supply: spinal segments T9, T10 Rotation:

On axis of SMA 270° anticlockwise 6- 10/40 gestation Via physiological hernia

Retroperitoneal: duodenum, ascending colon

Midgut rotation 6-10/40

Rotation occurs around the axis of the SMA on a single mesentery, “the mesentery”

Hindgut

Mid-transverse colon- upper anal canal Artery: IMA Nerve supply: T11 -S4 Mesenteries:

transverse mesocolon (shared with midgut) sigmoid mesocolon

Rotation: swings to left vertical axis of dorsal mesentery

Retroperitoneal: L colon (line of Toldt), rectum

Peritoneal Attachments

Bare area of liver

Lesser sac

Epiploic foramen

Greater sac

Abdominal Viscera

Next time!

Any Questions?

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