CHAPTER 22

INTRODUCTION TO THE UPPER LIMB, BACK, THORAX, AND ABDOMEN

Overview and Topographic Anatomy

Osteology

Muscles

Contents of the Thorax

Contents of the Abdomen

Vascular Supply

Nerve Supply

Questions

Overview and Topographic Anatomy

GENERAL INFORMATION

Osteology

UPPER LIMB

BACK

THORAX

ABDOMEN

Muscles

UPPER LIMB

BACK

THORAX

ABDOMEN

Contents of the Thorax

PLEURAL CAVITY

There are 2 pleural cavities

The cavity is composed of a 2-layered pleural sac that secretes a thin layer of serous fluid

• Visceral layer—lines the lung and fissures

• Parietal layer—lines the wall of the cavity

• Costal—lines the cavity along the ribs

• Mediastinal—lines the cavity along the mediastinum

• Diaphragmatic—lines the cavity along the diaphragm

• Cervical (cupula)—lines the cavity forming a dome in the ribs opposite the apex of the lung

Pleural reflections—Abrupt lines where the parietal pleura folds back or changes direction

• Vertebral (posterior)—where costal pleura is continuous with the mediastinal pleura at the vertebral column

• Costal (inferior)—where costal pleura is continuous with diaphragmatic pleura

• Sternal (anterior)—where costal pleura is continuous with the mediastinal pleura posterior to sternum

Boundaries

• Anterior midline—6th rib (right) 4th rib (left)

• Midclavicular line—8th rib

• Midaxillary line—10th rib

• Scapular line—12th rib

Inferior border of lungs in quiet respiration

• Anterior midline—6th rib (right) 4th rib (left)

• Midclavicular line—6th rib

• Midaxillary line—8th rib

• Scapular line—10th rib

Pleural recesses—potential spaces in the pleural cavity where parts of the parietal pleura contact one another during quiet respiration

• Costomediastinal—potential space where costal and mediastinal pleurae come together

• Costodiaphragmatic—potential space where costal and diaphragmatic pleurae come together

Pulmonary ligament—a fold created where the mediastinal pleura at the root of the lung come together and extend inferiorly

LUNGS

MEDIASTINUM

Region in the middle of the thorax between the two pleural sacs

Subdivided into superior and inferior

HEART

Contents of the Abdomen

STOMACH

Part of the foregut

There are 4 anatomical parts of the stomach:

• Cardia—where esophagus enters the stomach

• Fundus—created by the superior portion of the greater curvature

• Body—primary central area

• Pylorus—inferior portion that continues to narrow until reaching the pyloric sphincter

The mucosal lining of the stomach are raised elevations known as gastric rugae

There are 2 major curvatures:

• Greater curvature—provides attachment for some remnants of the dorsal mesogastrium:

• Gastrophrenic

• Gastrosplenic

• Greater omentum

• Lesser curvature—provides attachment for remnants of the ventral mesogastrium:

• Lesser omentum

• Hepatogastric portion (hepatoduodenal portion does not attach to the stomach)

There are 2 sphincters associated with the stomach:

• Esophageal—not an anatomical sphincter

• Pyloric—has a thick muscular sphincter

Receives extensive autonomic nerve supply

Is supplied by branches of the celiac artery

Releases pepsin and hydrochloric acid to aid in digestion

DUODENUM

Is the first of the 3 parts of the small intestine:

• Duodenum

• Jejunum

• Ileum

Part of the foregut and midgut

There are 4 anatomical parts of the duodenum:

• 1st part—intraperitoneal, part of foregut

• 2nd part—retroperitoneal, part of foregut

• Minor duodenal papilla—where accessory pancreatic duct (if present) drains

• Major duodenal papilla—where pancreas, liver, and gallbladder drain

• 3rd part—retroperitoneal, part of midgut

• 4th part—retroperitoneal, part of midgut

The mucosal lining of the duodenum are raised elevations known as plicae circulares

Receives extensive autonomic nerve supply

Is supplied by branches of the celiac and superior mesenteric arteries

Is the portion of the small intestine where the majority of chemical digestion occurs

A major histological feature is the presence of mucus-secreting glands, Brunner’s glands

JEJUNUM AND ILEUM

Are the final 2 parts of the small intestine:

• Duodenum

• Jejunum

• Ileum

Part of the midgut

Is intraperitoneal

Is suspended by the mesentery proper

The mucosal lining has raised elevations known as plicae circulares

Receives extensive autonomic nerve supply

Is supplied by branches of the superior mesenteric artery

JEJUNUM

Is about 7—8 feet in length

Has scattered lymphatic nodules and very few Brunner’s glands

Has prominent plicae circulares

Vascular supply has large prominent arterial arcades terminating with long vasa recta

ILEUM

Is about 6—12 feet in length

Ileum has extensive Peyer’s patches (lymphatic nodules)

Has fewer plicae circulares than the jejunum

Vascular supply has large smaller layers of arterial arcades terminating with short, compact vasa recta

Ends in the large intestine at the ileocecal valve

Is the embryological connection to the umbilicus via the vitelline duct; a Meckel’s diverticulum is a remnant of the duct in the adult

LARGE INTESTINE

Is divided into:

• Cecum with appendix

• Ascending colon

• Transverse colon

• Descending colon

• Sigmoid colon

• Rectum

Has the following characteristic features:

• Taeniae coli—3 separate bands of longitudinal muscle

• Haustra—pouch-like appearance caused by the contraction of the taeniae coli

• Epiploic appendages—small pouches of fat along the peritoneum

Part of the midgut and hindgut

Is intraperitoneal and retroperitoneal

The mucosal lining has raised elevations known as plicae semilunares

Receives extensive autonomic nerve supply

Is supplied by branches of the superior mesenteric and inferior mesenteric arteries

Major function is the absorption of water from the indigestible waste and expulsion from the body

CECUM

Is intraperitoneal

Connects ileum to the large intestine at the ileocecal valve

Blind pouch

Appendix is a small (typically around 4 inches) blind tubular intraperironeal structure connected to the cecum

ASCENDING COLON

Is retroperitoneal

Begins at ileocecal valve and ascends

Makes a colic impression on the liver and makes a sharp turn to the left side of the body known as the right colic (hepatic) flexure before continuing as the transverse colon

TRANSVERSE COLON

Is intraperitoneal, suspended by the transverse mesocolon

Longest portion of the large intestine

At the area of the spleen, makes a sharp turn to travel inferiorly, known as the left colic (splenic) flexure before continuing as the descending colon

DESCENDING COLON

Is retroperitoneal

Descends until it ends at the sigmoid colon

Terminal portion of the descending colon is often called the iliac colon because it lies in the iliac fossa

Typically has a smaller diameter than the ascending colon

SIGMOID COLON

Is intraperitoneal, suspended by the sigmoid mesocolon

Begins at the level of the pelvic brim

Travels toward the midline, where it ends at the rectum

RECTUM

Begins as intraperitoneal, but is retroperitoneal until it passes through the pelvic floor

Is about 4—5 inches in length

Does not have taeniae coli as the separate bands merge to form a complete band of longitudinal muscle at the rectum

Ends at the anus

LIVER

Large, multifunctional organ, including:

• Detoxification

• Glycogen storage

• Production of hormones

• Synthesis of plasma proteins

• Production of bile

Divided into 4 anatomical lobes:

• Right—largest lobe

• Caudate—located between fissure for the ligamentum venosum and the inferior vena cava

• Quadrate—located between fissure for the ligamentum teres hepatis (round ligament of the liver) and the gallbladder

• Left—flattened lobe

Is further subdivided into functional segments based on the vascular supply

Is completely covered by visceral peritoneum except an area where the liver connects with the diaphragm, known as the bare area

The porta hepatis is the central portion of the liver where the following structures enter and exit:

• Hepatic portal vein—provides 75% of the blood to the liver

• Proper hepatic artery—provides 25% of the blood to the liver

• Common bile duct

Is intraperitoneal

Is supplied by branches of the celiac artery

All remnants of the ventral mesentery attach to the liver:

• Falciform ligament

• Coronary ligament

• Triangular ligament

• Lesser omentum

• Hepatogastric ligament

• Hepatoduodenal ligament

The liver is subject to numerous pathologies, including:

• Hepatitis

• Cirrhosis

• Cancer

PANCREAS

The pancreas functions as 2 types of glands:

• Endocrine—Islets of Langerhans producing hormones

• Exocrine—Compound tubuloalveolar pancreatic acini producing digestive enzymes

Comprised of 4 major parts:

• Head—is located in the “C” or curve formed by the duodenum; is retroperitoneal

• Uncinate process—an extension of the head crossed by the superior mesenteric vv.

• Neck—constricted portion of pancreas connecting the head to the body; is retroperitoneal

• Body—largest part of the pancreas separated from the stomach by the omental bursa, is retoperitoneal

• Tail—extends into the lienorenal ligament with the splenic vv. to the spleen

Is part of the foregut

Develops as 2 separate outgrowths from the 2nd part of the duodenum:

• Ventral pancreatic bud—an outgrowth of the hepatic bud

• Develops into the head and neck of the pancreas

• Dorsal pancreatic bud—a direct outgrowth of the 2nd of the duodenum

• Develops into the body and tail of the pancreas

Drains into the 2nd part of the duodenum

• Main pancreatic duct—drains into the major duodenal papilla by joining the common bile duct forming the hepatopancreatic ampulla

• Accessory pancreatic duct—drains into the minor duodenal papilla (if present and patent)

Is supplied by branches of the celiac and superior mesenteric arteries

Receives extensive autonomic nerve supply

GALLBLADDER AND DUCT SYSTEM

GALLBLADDER

Small intraperitoneal organ

Is part of the foregut

Stores and concentrates bile, which emulsifies fat during digestion

Is located in a fossa on the liver where the linea semilunaris attaches to the ribcage at the 9th costal cartilage

Divided into 3 parts:

• Fundus

• Body

• Neck

Is supplied by branches of the celiac artery

Receives extensive autonomic nerve supply

DUCT SYSTEM

The cystic duct joins the common hepatic duct to form the common bile duct

The common bile duct joins the main pancreatic duct within the substance of the pancreas to form the hepatopancreatic ampulla, which passes through the wall of the 2nd part of the duodenum into the major duodenal papilla

SPLEEN

A lymphatic organ on the left side of the body divided into:

• Red pulp

• White pulp

Is intraperitoneal

• Major functions include:

• Storage of red blood cells

• Filters red blood cells

• Removes old red blood cells

• Storage of monocytes

Is not a derivative of the foregut, although receives its arterial supply from branches of the celiac artery

Is located between the 9th and 11th ribs, paralleling the 10th rib

Has contact with 4 organs:

• Stomach

• Large intestine

• Left kidney

• Tail of pancreas

Is suspended by dorsal mesentery of the foregut:

• Lienorenal—contains tail of the pancreas and splenic vv.

• Gastrosplenic—contains short gastric vv. and left gastroepiploic vv.

KIDNEY, URETER, AND SUPRARENAL GLAND

KIDNEY

Paired organ

Is retroperitoneal

Has multiple functions, including:

• Filter blood

• Regulate electrolytes

• Regulate blood pressure

• Produce hormones

Nephron is function unit

Located between T11—L3, with hilum at L1

Left kidney is slightly larger than the right kidney

Right kidney is slightly inferior to the left kidney due to the liver

Surrounded by a tough capsule

Divided into:

• Cortex

• Medulla

Receives arterial supply from renal vv.

Receives extensive autonomic nerve supply

URETER

Is retroperitoneal

Carries urine from kidney to the bladder

Begins at hilum, or L1 and travels inferior to the bladder

Common sites of kidney stones include:

• Uteropelvic junction

• Crossing Iliac vv. on pelvis

• Junction with bladder

SUPRARENAL GLAND

Also known as adrenal gland

Are endocrine glands

Divided into:

• Cortex—responsible for production of mineralocorticoids, glucocorticoids, and androgens

• Medulla—responsible for catecholamines via sympathetic response (flight or flight)

Receives threefold arterial supply:

• Superior suprarenal—from inferior phrenic a.

• Middle suprarenal—from aorta

• Inferior suprarenal—from renal a.

Vascular Supply

UPPER LIMB

Arterial Supply of the Axilla

Axillary—is divided into 3 parts based on its relationship to the pectoralis minor

• 1st part

• Superior thoracic—supplies 1st two intercostal spaces

• 2nd part

• Thoracoacromial

• Pectoral

• Acromial

• Deltoid—accompanies cephalic v.

• Clavicular—helps supply acromioclavicular joint

• Lateral thoracic—follows inferior border of pectoralis minor to thorax

• 3rd part

• Subscapular

• Scapular circumflex—located in triangular space

• Thoracodorsal—passes with thoracodorsal n. to latissimus dorsi

• Posterior humeral circumflex—travels in quadrangular space with axillary n.

• Anterior humeral circumflex

Arterial Supply of the Brachium

Brachial—begins at inferior border of teres major

• Profunda brachii

• Middle collateral

• Radial collateral

• Superior ulnar collateral—passes with ulnar n. posterior to medial epicondyle

• Inferior ulnar collateral

• Muscular branches

Arterial Supply of the Antebrachium

Brachial—divides into:

• Radial

• Radial recurrent

• Palmar carpal branch

• Superficial palmar branch

• Ulnar

• Anterior ulnar recurrent

• Posterior ulnar recurrent

• Common interosseous

• Palmar carpal branch

Carpus and Manus

Ulnar

• Dorsal carpal branch

• Deep branch of the ulnar

• Palmar carpal branch

• Superficial palmar arch

• Common palmar digital

• Proper palmar digital

Radial

• Princeps pollicis

• Radialis indicis

• Deep palmar arch

Veins

Two types of veins:

• Superficial—lie in superficial fascia

• Cephalic

• Basilic

• Deep (have either):

• Single similar-sized vein following the artery of the upper limb (e.g., subclavian vein or axillary vein)

• Vena comitans—accompanying vein

• A pairing of veins with both surrounding the artery

• Typically any veins that are distal to the axillary v. is a vena comitans (e.g., brachial veins, ulnar veins, and radial veins), which are paired around the artery of the same name

THORAX

Arterial

• Internal thoracic—arises from subclavian a.

• Pericardiacophrenic

• Terminates as:

• Musculophrenic

• Superior epigastric

• Intercostal arteries

• Posterior intercostal

• 2 (Costocervical trunk)

• 9 (Thoracic aorta)

• 1 Subcostal (thoracic aorta)

• Anterior intercostal

• 6 (Internal thoracic)

• 3 (Musculophrenic)

• Esophageal

• Bronchial

• Right (3rd posterior intercostal a.)

• 2 Left (aorta)

Veins

▪ Azygos system

• Posterior intercostal vv.

• Esophageal vv.

• Bronchial vv.

• Right side of thorax

• Right supreme intercostal v.

• Right superior intercostal v.

• Left side of thorax

• Left supreme intercostal v.

• Left superior intercostal v.

• Accessory hemiazygos v.

• Hemiazygos v.

ABDOMEN

Unpaired Visceral Arteries

Celiac Artery (Artery of the Foregut)—arises at T12

• Left gastric

• Common hepatic

• Proper hepatic

• Right gastric

• Left hepatic

• Right hepatic

• Cystic

• Gastroduodenal

• Supraduodenal

• Right gastroepiploic

• Anterior and posterior superior pancreaticoduodenal

• Splenic

• Pancreatic branches

• Short gastric

• Left gastroepiploic

Superior Mesenteric Artery (Artery of the Midgut)—arises at L1

• Anterior and posterior inferior pancreaticoduodenal

• Jejunal mesenteric

• Arterial arcades and vasa recta

• Ileal mesenteric

• Arterial arcades and vasa recta

• Ileocolic

• Appendicular

• Right colic

• Middle colic

Inferior Mesenteric Artery (Artery of the Hindgut)—arises at L3

• Left colic

• Sigmoid

• Superior rectal

POSTERIOR ABDOMEN

Paired Visceral and Parietal Arteries

Paired Visceral Branches—paired branches supplying organs

• Renal—arises at L2

• Gonadal—arises between L2 and L3

• Testicular

• Ovarian

• Suprarenal

• Superior—arises from the inferior phrenic

• Middle—arises from the aorta

• Inferior—arises from the renal

Paired Parietal (Body Wall) Branches—paired branches supplying the wall

• Inferior phrenic

• Lumbar—4 arise from the aorta

ABDOMEN

Venous Supply of the Viscera

Veins that drain the abdominal viscera closely follow the celiac, superior mesenteric, and inferior mesenteric arteries

These veins eventually drain into the hepatic portal vein, which passes into the liver, allowing the liver to clear the blood of any wastes and to store nutrients

The hepatic portal vein is formed by the:

• Superior mesenteric vein

• Splenic vein

After passing through the liver, the blood returns into the systemic system via hepatic veins into the inferior vena cava

Since the veins in this region lack valves, they take the path of least resistance

If there is an obstruction in the path of the hepatic portal vein, the blood will attempt to return the blood toward the heart by bypassing the block and utilizing anastomosis between the portal system and the systemic system (vena cava)

There are 4 major collaterals between the portal and systemic systems:

• Esophageal

• Paraumbilical

• Rectal

• Retroperitoneal

Hepatic Portal Vein

• Minor direct tributaries include:

• Cystic v.

• Right gastric v.

• Left gastric v.

• Esophageal vv.

• Posterior superior pancreaticoduodenal v.

• Major tributaries include:

• Superior mesenteric vein

• Right gastroepiploic v.

• Anterior superior pancreaticoduodenal v.

• Anterior inferior pancreaticoduodenal v.

• Posterior inferior pancreaticoduodenal v.

• Middle colic v.

• Jejunal mesenteric vv.

• Venous anastomotic loops

• Vasa recta

• Ileal mesenteric vv.

• Venous anastomotic loops

• Vasa recta

• Ileocolic v.

• Right colic v.

• Splenic v.

• Pancreatic branches

• Short gastric v.

• Left gastroepiploic v.

• Inferior mesenteric—sometimes joins to form hepatic portal v.

• Left colic v.

• Sigmoid vv.

• Superior rectal v.

POSTERIOR ABDOMEN

Venous Supply of the Posterior Abdominal Wall

Veins of the posterior abdominal wall drain into the inferior vena cava

Tributaries include:

• Hepatic vv.

• Right hepatic v.

• Middle hepatic v.

• Left hepatic v.

• Inferior phrenic v.

• Suprarenal v.

• Renal v.

• Left gonadal v.

• Testicular

• Ovarian

• Right gonadal v.

• Testicular

• Ovarian

• Subcostal v.

• Lumbar vv.

Nerve Supply

UPPER LIMB

Alternating joining and branching of nerves to reorganize the terminal branches with contributions from multiple spinal cord levels

Origin from ventral rami of 5th to 8th cervical and 1st thoracic spinal nerves

General organization is:

• 5 Ventral rami

• 3 Trunks

• 6 Divisions

• 3 Cords

• 6 Branches

Nerves to muscles on ventral and dorsal surfaces of upper limb are derived from anterior and posterior divisions, respectively.

Location and arterial relations:

• Rami and trunks—Posterior triangle of neck—Subclavian a.

• Divisions—Behind clavicle—Subclavian and 1st part of axillary a.

• Cords—Axilla—2nd part of axillary a.

• Branches—Axilla—3rd part of axillary a.

Key landmark of “M” formed by medial and lateral cords and terminal branches

UPPER LIMB

POSTERIOR ABDOMINAL WALL

Nerves

• Subcostal—T12

• Iliohypogastric—L1

• Ilioinguinal—L1

• Lateral femoral cutaneous nerve—L2, L3

• Genitofemoral—L1, L2

• Genital branch—cremaster

• Femoral branch—sensory on thigh

• Femoral—L2, L3, L4

• Obturator—L2, L3, L4