Week 4: Abdomen & Pelvis

Peritoneum

Serous membrane that lines the abdominal cavity

Visceral Peritoneum

The inner layer of the peritoneum that surrounds the organs of the abdominopelvic cavity

Parietal Peritoneum

The outer layer of the peritoneum that lines the interior of the abdominopelvic wall

Transumbilical Plane (L3/4 disc)

Divides the abdomen into upper and lower halves

Peritoneal cavity

A potential space containing peritoneal fluid, between the parietal and visceral layers of the peritoneum. Within the abdominal cavity and continues inferiorly into the pelvic cavity

Abdominal Viscera in RUQ

Liver: Right Lobe
Gallbladder
Stomach: Pylorus
Duodenum: Parts 1-3
Pancreas: Head
Right suprarenal gland
Right Kidney
Right colic (hepatic) flexure
Ascending colon: superior part
Transverse colon: right half

LUQ Viscera

Liver: Left Lobe
Spleen
Stomach
Jejunum and proximal ileum
Pancreas: body and tail
Left kidney
Left suprarenal gland
Left colic (hepatic) flexure
Transverse colon: left half
Descending colon: superior part

RLQ viscera

Cecum
Appendix
Most of ileum
Ascending colon: inferior part
Right ovary
Right uterine tube
Right Ureter: abdominal part
Right spermatic cord: abdominal part
uterus (if enlarged)
Urinary bladder (if very full)

LLQ viscera

Sigmoid colon
Descending colon: inferior part
Left ovary
Left Uterine tube
Left Ureter: abdominal part
Left spermatic cord: abdominal part
Uterus (if enlarged)
Urinary bladder (if very full)

External Oblique Origin

External surfaces of 5th-12th ribs

External Oblique Insertion

Linea alba, pubic tubercle, and anterior half of iliac crest

External Oblique innervation

Thoracoabdominal nerves (T7-T11 spinal nerves) and subcostal nerve

External Oblique Action

Unilateral: Trunk Contralateral Rotation
Bilateral: Trunk Flexion
Compress & Support Abdominal Viscera

External oblique fiber orientation

Inferomedially

Internal Oblique Origin

Lower fibers: connective tissue deep to lateral third of inguinal ligament

Mid-upper fibers: Thoracolumbar fascia & anterior two thirds of iliac crest

Internal Oblique Insertion

Inferior borders of 10th-12th ribs, Linea alba, and Pecten pubis via conjoint tendon

Internal Oblique Innervation

Thoraco-abdominal nerves (anterior rami of T6-T12 spinal nerves) and first lumbar nerve

Internal Oblique Action

Unilateral: Trunk Ipsilateral Rotation
Bilateral: Trunk Flexion
Compress & Support Abdominal Viscera

Internal oblique fiber orientation

Superomedial

Transversus Abdominus Origin

Internal surfaces of 7th-12th costal cartilages

Thoracolumbar fascia

Iliac crest

Lateral third of the inguinal ligament

Transversus Abdominus insertion

Line alba with aponeurosis of internal oblique, pubic crest, and pecten pubis via conjoint tendon

Transversus Abdominus innervation

Thoracoabdominal nerves (ventral rami of T6-T12 spinal nerves) and first lumbar nerve

Transversus Abdominus Action

Compresses and supports abdominal viscera

Transverse Abdominis fiber orientation

Transverse

Rectus Abdominus Origin

Pubic crest and pubic symphysis

Rectus Abdominus insertion

Xiphoid process and costal cartilages of ribs 5-7

Rectus Abdominus innervation

Thoraco-abdominal nerves (anterior rami of T6–T12 spinal nerves)

Rectus Abdominus action

Flexes trunk (lumbar vertebrae) and compresses abdominal viscera

Stabilizes and controls tilt of pelvis (antilordosis)

3 Flat muscles of the Anterolateral Abdominal wall

• External oblique

• Internal oblique

• Transverse abdominis

These form Rectus Sheath & Linea Alba via aponeuroses

2 Vertical muscles of the Anterolateral Abdominal wall

• Rectus abdominis

• Pyramidalis

What is the significance, clinically, for the internal oblique and transversus abdominus muscles to attach to the thoracolumbar fascia?

Together, they form a muscular girdle that puts pressure on abdominal viscera which increases intra-abdominal pressure and elevates the relaxed diaphragm during forced expiration - cough, sneeze

What are other movements that the abdominal muscles can do individually or combined?

Increase Intra-abdominal pressure:

- Forced expiration

- Defecation

- Micturition (urination)

- Vomiting

- Childbirth

- Heavy lifting

Trunk movements & pelvis tilting

- Rectus abdominis flexes trunk (or posteriorly tilts pelvis)

- Obliques laterally flex & rotate trunk

What layers would you have to cut through from posterior to anterior to reach the kidneys?

External Oblique —> Aponeurosis of Transversus abdominus —> Quad Lumborum

Parietal peritoneum characteristics

Lines internal wall

- Sensitive to pressure, pain, heat, cold, laceration

- Pain localized

Visceral peritoneum characteristics

Line organs

- Sensitive to stretching & chemical irritation

- Pain referred to dermatomes

Intraperitoneal

Completely surrounded by visceral peritoneum

Extraperitoneal

Outside the peritoneum

Retroperitoneal

Behind the peritoneum

Subperitoneal

Inferior to parietal peritoneum; superior surface of the organ is covered with parietal peritoneum

Intraperitoneal organs

Stomach

Jejunum and Ileum

Transverse and sigmoid colon

Appendix

Liver

Spleen

Extraperitoneal organs

Organs outside of the parietal peritoneum, but typically covered by parietal peritoneum on one side

Retroperitoneal organs

Located outside, or posterior to, the peritoneum
Includes most of pancreas, duodenum, and parts of large intestine

Subperitoneal organs

Bladder

Prostate

Rectum

What passes through the Caval Opening

IVC

Right Phrenic Nerve

Lymphatic Vessels going to the liver

What passes through the Esophageal Hiatus

Esophagus

Vagal trunks

Gastric vessels

Lymphatic vessels

Right crus

What passes through the Aortic Hiatus (Median Arcuate Ligament)

Descending aorta

Thoracic duct

Azygous vein

Hemi-azygous vein

Median Arcuate Ligament

Joins the R & L crura and forms the Aortic Hiatus

What Passes through Medial Arcuate Ligament

Psoas major

What passes through the Lateral Arcuate Ligament

Quadratus lumborum

Level of Caval opening of the diaphragm

Level of T8-9

Level of Esophageal Hiatus of the diaphragm

Level of T10

Level of Aortic Hiatus of the diaphragm

Level of T12

Veins from Abdominopelvic region to Inferior Vena Cava (IVC)

R&L Common Iliac Veins

Hepatic Portal Vein tributaries

Right Suprarenal Vein

R&L Renal Veins —> Inferior Vena Cava

Right Gonadal Vein

Inferior Phrenic Veins

L3 & L4 Lumbar veins

Basic flow of Lymph in Posterior Abdominal wall

Internal & External Iliac lymph nodes —> Common Iliac lymph nodes —> Lumbar lymph nodes —> Pre-Aortic lymph nodes —> Intestinal lymphatic trunks

Intestinal lymphatic trunks + Lumbar lymphatic trunks + Thoracic lymphatic trunks = Cisterna Chyli

Cisterna Chyli —> Thoracic duct —> Left Subclavian vein —> Internal jugular vein —> Left Venous Angle

What are Hiatal Hernias?

When the stomach protrudes into the thorax through the Esophageal Hiatus of the diaphragm

Type of Hiatial Hernias

• Para-esophageal

• Sliding

Para-esophageal Hernia

- Less common

- Fundus and pouch of peritoneum protrude

- No regurgitation because Cardia stays in place

Sliding Hernia is more or less common

More

Sliding Hernia

- Abdominal esophagus, cardia, and fundus move superiorly through hiatus when laying down or bending over

- Regurgitation possible due to weak right crus of diaphragm

What are Abdominal Hernias?

Occurs when a structure pierces the abdominal wall, creating a potential weakness

Type of Abdominal Hernias

• Epigastric

• Umbilical

Epigastric Hernia

- Protrudes through Linea alba

- Usually fat lobules in the hernia

- Painful if nerves get compressed

Umbilicial hernia

- Weakness from incomplete closure of umbilical ring

- Common in neonates

- Acquired in adults-most commonly women and obese individuals

Diastasis Recti

- Linea Alba widens due to intra-abdominal pressure from pregnancy or obesity

- Rectus Abdominis columns separate creating area of weakness in anterior abdominal wall

- Structures can herniate in epigastric or umbilical regions

What are Inguinal Hernias?

Protrusions of parietal peritoneum and and viscera

- More common in males because of the passage of the spermatic cord through the inguinal canal

Types of Inguinal Hernias

• Direct

• Indirect

Direct Inguinal hernia

- Passes through or around inguinal canal

- Lateral to the spermatic cord

- Rarely enters the scrotum

- Palpable at superficial inguinal ring

Indirect inguinal hernia

- Most common type
- Inside spermatic cord
- The hernia passes down the inguinal canal and exits at the external inguinal ring into the scrotum.
- Palpable at superficial and deep inguinal rings

2 Gridiron incisions

• McBurney

• Suprapubic

McBurney incision conditions

Appendectomy

What gridiron incision spares muscle walls

McBurney

McBurney muscles

External Obliques

Suprapubic incision

“Bikini” Incision; A transverse incision just superior to the pubic hair line

Suprapubic incision conditions

C-section

Peritonitis

Inflammation of the peritoneum, the serous membrane that surrounds the abdominal cavity and covers its organs

Peritonitis causes

• Bacterial contamination from surgery

• Traumatic penetration or rupture in gut

Peritonitis symptoms

• Pain in overlying skin

• Increased muscle tone

• Tenderness, N/V, fever, constipation

Generalized Peritonitis

• Widespread in peritoneal cavity

• Dangerous & lethal because peritoneal surfaces rapidly absorb material

Acities

The accumulation of fluid within the peritoneal cavity

• Distended abdomen

Ascites causes

• Mechanical injury —> internal bleeding

• Portal hypertension

• Metastasis of CA cells

• Starvation

Peritoneal Adhesions

Adhesions = scar tissues

Peritoneum damage = inflamed surfaces = sticky from fibrin

• Fibrin replaces with scar tissue during healing

Limits visceral movement, Causes chronic pain

Hiccups

Involuntary spasm of diaphragm

• sudden inhalation

• spasmodic closure of the glottis

Causes of hiccups

• Irritation of afferent or efferent nerve endings, or medullary centers in brainstem

• Indigestion

• Diaphragm irritation

• Alcoholism

• Lesions disturbing phrenic nerves: cerebral, thoracic, abdominal

Diaphragmatic referred pain

Shoulders and Costal margins

Phrenic diaphragmatic Pain

Shoulder

Inferior intercostal nerves diaphragmatic pain

Costal Margins

Abdominal Aortic Aneurysm (AAA)

Abnormal & excessive dilation or ballooning of abdominal aorta

Acute rupture = FATAL (90%)

AAA causes

• Congenital

• Acquired weakness of arterial wall

Imaging confirms diagnosis

Distend

Expand; swell out

Ingest

To swallow for digestion

Digest

To break down food

Raphe

Seam of fibrous tissue

Navel

Umbilical

Decussate

Cross over

Rectus

Straight

Micturition

Urination

Defecation

Elimination of feces

Hernia

Protrusion of an organ or part through the tissues and muscles normally containing it

Spermatogenesis

Formation of sperm

Path of food from entrance to exit

1. Mouth: teeth, tongue, salivary glands form bolus
2. Oropharynx: after being swallowed epiglottis closes over trachea
3. Esophagus
4. Stomach
5. Small intestine: Duodenum —> Jejunum —> Ileum
6. Large intestine: Cecum —> Ascending Colon —> Transverse Colon —> Descending Colon —> Sigmoid Colon
7. Rectum
8. Anal canal