Anatomy: The Abdomen I

superior = diaphragm

inferior = muscles of the pelvis

anterolaterally = musculoaponeurotic walls

protect + enclose abdominal contents

flexibility = for respiration, posture, locomotion

Transverse:

• subcostal plane (most superior)

• transtubercular plane (most inferior)

Sagittal:

• midclavicular lines (x2)

1. Right hypochondriac

2. Right lumbar

3. Right inguinal

4. Epigaastric

5. Umbilical

6. Hypogastric

7. Left hypochondriac

8. Left lumbar

9. Left inguinal

Superior = midclavicular planes; pass approximately 9 cm from the midline

inferior = midinguinal points; midway between the anterior superior iliac spine and the superior edge of the pubic symphysis on each side

subcostal plane = passes through inferior border of the 10th costal cartilage on each side

transtubercular plane = passes through the iliac tubercles (approx. 5 cm posterior to anterior superior iliac spine) + body of L5

approximate midpoint between:

superior border of manubrium + superior border of pubic symphysis

(L1 vertebral level)

• comonly transects the pylorus (distal part of stomach)

• fundus of gallbladdar

• neck of pancreas

• origins of superior mesenteric artery & portal vein

• root of transverse mesocolon

• duodenojejunal junction

• hila of kidneys

anterior superior iliac spine on each side

(easily palpated)

posterior abdominal wall

(includes lumbar vertebral column)

thoracic cage to the pelvis

superior = 7th - 10th rib cartilages + xiphoid process

inferior = inguinal ligament + superior margins of the anterolateral aspects of the pelvic girdle (iliac crests, pubic crests, + pubic symphysis).

1. 
   external oblique

2. internal oblique

3. transverse abdominis

1. Camper fascia (superficial, fatty, subcutaneous)

2. Scarpa fasca (deep, membranous, subcutaneous)

3. a) Superficial Investing (deep) fascia

4. b) Intermediate Investing (deep) fascia

5. c) Deep Investing (deep) fascia

6. Endoabdominal (transversalis) fascia

1. skin (cut edge)

2. extraperitoneal fat

3. parietal peritoneum

at the unbilicus

b/c the abdomin is a positive pressure area

• higher chance of herniation so intersecting fibers = added strength

FAT

too much fat** = obesity;** can cause sagging folds “panniculi” (apron)

• face

• bottocks

fun facts from Dr. Ray :)

1. many elastic and collagen fibers

2. Camper fascia = superficial fatty layer
   - Scarpa fascia = deep membranous layer

perineal region as the superficial perineal fascia (Colles fascia)

NOT into the thighs (fascia lata)

Significant because:

fluids** escaping from a ruptured vessel or urethra (blood and/or urine) may **accumulate deep to it

the external aspects of the three muscle layers of the anterolateral abdominal wall + their aponeuroses (flat expanded tendons)

the internal aspect of the abdominal wall

"transversalis fascia"

| (relatively firm)

"parietal peritoneum"

(internal to transversalis fascia; separated by extraperitoneal fat)

1. potential space b/t membranous layer of subcutaneous tissue + deep fascia (covering rectus abdominis + external oblique m.)

fluid may accumulate

• cannot spread inferiorly into the thigh because the membranous layer fuses with the deep fascia of the thigh (fascia lata)

1. helps protect against contamination therefore, during surgeries, entry into the periotoneal cavity is aoided as much as possible.

it can be opened during surgery

• access structures on/in anterior aspect of posterior abdominal wall without entering the peritoneal sac

• minimize risk of contamination

• Space of Bogros = b/t transversalis fascia + parietal peritoneum; anterolateral part of potential space used for placing prostheses (ex. when repairing inguinal hernias);

5 muscles

• 3 flat (external oblique, internal oblique, and transverse abdominal)

• 2 verticle (rectus abdominis, pyrimidalis)

external oblique

internal oblique

transverse abdominal

origin: External surfaces of 5th - 12th ribs

insertion: Linea alba, pubic tubercle + anterior half of iliac crest

innervation: Thoracoabdominal nerves (T7 - T11) + subcostal nerve

• - largest, most superficial*

• - run inferomedially*

• - left superficial become right deep; Right superficial become left deep @ linea alba*

• - continued anteromedially as aponeurosis*

aponeuroses

| (strong, sheet-like)

• between the midclavicular line and the midline (medially)

• at the spinoumbilical line; running from umbilicus to anterior superior iliac spine (inferiorly)

• most become continuous with tendinous fibers of the contralateral internal oblique*

• interweaved aponeuroses form a midline raphe

• extends from xiphoid process to the pubic symphysis

1. aponeurosis fibers interweave from:

• right + left sides

• superficial + intermediate; intermediate + deep layers

1. "rectus sheath"

2. contains the rectus abdominis + pyramidalis

Inferior attachment = pubic crest (medial to pubic tubercle)

inferior margin = inguinal ligament (thickened fibrous band; free posterior edge spanning b/t anterior superior iliac spine + pubic tubercle)

• continuous inferiorly w. deep fascia of thigh

• acts as a retinaculum (retaining band) for structures passing deep to it

(iliopsoas muscle + femoral vessels + nerve)

most herniations happen here = weak area

Origin: Thoracolumbar fascia, anterior two-thirds of iliac crest + lateral half of inguinal ligament

Insertion: Inferior borders of 10th - 12th ribs, linea alba + pecten pubis via conjoint tendon

Innervation: Thoracoabdominal nerves (anterior rami of T7-T12 nerves) + first lumbar nerves

Main action: Compress + support abdominal viscera; flex + rotate trunk

• - deep to extrenal; superficial to transversus*

• - run anterosuperiorly*

Origin: Internal surfaces of 7th - 12th costal cartilages, thoracolumbar fascia, iliac crest + lateral third of inguinal ligament

Insertion: Linea alba w. aponeurosis of internal oblique, pubic crest + pecten pubis via conjoint tendon

Innervation: Thoracoabdominal nerves (anterior rami of T7-T12 nerves) first lumbar nerves

Main action: Compresses + supports abdominal viscera

• - run transverly*

• - deep to internal obliques*

• long, broad, strap-like muscle

(broad + thin superiorly; narrow + thick inferiorly)

• principal vertical muscle of anterior abdominal wall

• paired rectus muscles; separated by the linea alba; lie close together inferiorly

• Most of rectus abdominis is enclosed in rectus sheath

• anchored transversely by attach. to anterior layer of the rectus sheath (three or more tendinous intersections)

• sometimes herniation may occur; connection not strong

• level of xiphoid process

• umbilicus

• halfway between these two

Origin: Pubic symphysis and pubic crest

Insertion: Xiphoid process and 5th - 7th costal cartilages

Innervation: Thoracoabdominal nerves (anterior rami of T7-T12 nerves)

Main action: Flexes trunk (lumbar vertebrae) + compresses abdominal viscera; stabilizes and controls tilt of pelvis (balancing pelvis)

- absent in approximately 20% of people

• small, triangular muscle

• lies anterior to inferior rectus abdominis

• attaches to anterior surface of pubis + anterior pubic ligament

• ends in linea alba

• tenses linea alba (when present)

• strong, incomplete fibrous compartment of rectus abdominis + pyramidalis muscles

• formed by decussation + interweaving of aponeuroses of flat ab. muscles

• external oblique aponeurosis contributes to anterior wall of sheath throughout its length

• superior 2/3 of internal oblique aponeurosis splits into 2 layers (laminae) at the lateral border of rectus abdominis; one passes anterior, the other passes posterior

• anterior lamina joins aponeurosis of external oblique = anterior layer of sheath

• posterior lamina joins aponeurosis of the transverse abdominal = posterior layer of sheath

• approx. 1/3 of distance fr. umbilicus to pubic crest --> aponeuroses of 3 flat muscles pass anterior to rectus abdominis = anterior layer of sheath

• (fibers of anterior + posterior layers of sheath interlace @ anterior median line = linea alba)

• **(only thin transversalis fascia left to cover rectus abdominis posteriorly)*

because the transverse abdominal muscle pass internal to the costal cartilages and the internal oblique attaches to the costal margin…

→Form a strong expandable support for the anterolateral abdominal wall.

→Protect the abdominal viscera from injury.

→Compress the abdominal contents to maintain or increase the intra-abdominal pressure and, in so doing, oppose the diaphragm (increased intra-abdominal pressure facilitates expulsion).

→Move the trunk and help maintain posture.

• use warm hands (cold hands=anterolateral ab. muscles tense=guarding)

• guarding: reflexive muscular rigidity that cannot be willfully suppressed

--> sign of abdominal organ inflammation

--> involuntary muscular spasms attempt to protect viscera fr. pressure (painful when abdominal infection is present)

1. supine position with thighs and knees semiflexed

• adequate relaxation of the anterolateral abdominal wall

1. upper limbs at the sides +** putting a pillow under the knees **

• relax the anterolateral abdominal muscles

quickly stroking horizontally (lateral to medial) toward the umbilicus

• Usually, contraction of the abdominal muscles is felt

• - injury to the abdominal skin results in a rapid reflex contraction of the abdominal muscles.*

umbilical ring

• fetal umbilical vessels passed to/from umbilical cord and placenta

• All layers of anterolateral abdominal wall fuse at the umbilicus.*

• (Cannot distinguish b/t different fibers)*

• their gastrointestinal tracts contain considerable amounts of air

• their anterolateral abdominal cavities are enlarging and their abdominal muscles are gaining strength

• have a relatively large liver

Eversion of the umbilicus

- usually resulting from ascites (serous fluid accumulation) or a large mass (tumor; enlarged organ)

abdominal enlargement

it means it is already pathology (3x larger than normal)

cannot palpate a normal spleen

inguinal region

umbilical region

epigastric region

Umbilical hernias

(Herniation occurs through the umbilical ring)

• anterior abdominal wall is relatively weak in umbilical ring
  (esp. in low-birth-weight infants)

women + obese people

• extraperitoneal fat and/or peritoneum protrude into the hernial sac

- the lines where abdominal aponeuroses interlace

(ocassionally have gaps; ex. midline, transition fr. aponeurosis to r.sheath)

• gaps can be congenital due to stresses of obisity + aging

OR

consequences of surgery or trauma

occurs in midline b/t xiphoid process + umbilicus (through linea alba)

(usually problems with muscle fibers at this site = hernia)

occur along semilunar lines

• hernial sac = (peritoneum) covered w. skin + fatty subcutaneous tissue

• usually people more than 40 years

• usually associated with obesity

distal, abdominal parts of the anterior rami of T7 - T11

from the thoracic spinal nerves T7 - T9 or T10

large anterior ramus of spinal nerve T12

terminal branches of the anterior ramus of spinal nerve L1

inferior thoracic spinal nerves (T7 - T12)

+

iliohypogastric and ilioinguinal nerves (L1)

injury in surgical incisions or from trauma at any level of the abdominal wall

• weakening of the muscles

• predisposed to inguinal hernia

Made to follow the cleavage lines (Langer lines) in the skin

insicions chosen for:

1. adequate exposure

2. best possibly cosmetic effect

• the type of operation

• location of the organ(s) the surgeon wants to reach

• bony or cartilaginous boundaries

• avoidance of (especially motor) nerves

• maintenance of blood supply

• minimizing injury to muscles + fascia of the wall

• aiming for favorable healing

surgeon must consider direction of the muscle fibers + location of aponeuroses and nerves

pararectus and inguinal incisions

along the lateral border of the rectus sheath

• undesirable b/c likely to cut the nerve supply to the rectus abdominis

• blood supply from inferior epigastric artery also may be compromised

for repairing hernias

• may injure the ilioinguinal nerve directly; may be inadvertently included in the suture during closure of the incision

protrusion of omentum (a fold of peritoneum) or an organ through a surgical incision

• can result if muscular + aponeurotic layers of abdomen do not heal properly

• advanced age

• debility of patient

• obesity

• post-op. wound infection

tiny perforations of the abdominal wall allow the entry of remotely operated instruments

• replaces larger conventional incisions

• many abdominopelvic surgical procedures can be done this way

• potential for nerve injury, incisional hernia, or contamination through the open wound + the time required for healing are minimized

• surgeons should know both methods, as resources might not be available*