Extraocular Muscles : Function and Innervation

Eye Movement Control Systems

Extraocular Muscles : Function

Superior Oblique muscle : can depress and abduct the eye from the neutral position. From the adducted position, it is the only muscle that can depress the eye

Inferior Oblique muscle : can elevate and abduct the eye from the neutral position.From the adducted position, it is the only muscle that can elevate the eye

Superior rectus muscle : can elevate and adduct the eye from neutral position. it is the only muscle that can elevate the eye from the abducted position

Inferior rectus muscle : can depress and adduct the eye from the neutral position. From the abducted position , it is the only muscle that can depress the eye.

The Lateral rectus muscle can abduct the eye.

Innervation:

Cranial Nerve III :

• Medial rectus : adducts eye
• Superior rectus : elevate, intorts, adducts eye
• Inferior rectus  : depresses, extorts, adducts eye
• Inferior Oblique: elevates, extorts, abducts eye

Cranial Nerve IV : 

• Superior Oblique : depresses, intorts , abducts eye

Cranial Nerve VI : 

• Lateral rectus: Abducts eye.

Intraperitoneal and Retroperitoneal Organs

Major Intraperitoneal Organs: (suspended by a mesentery)

• Stomach
• Liver and Gallbladder
• Spleen
• Duodenum, 1st part
• Tail of pancreas
• Jejunum
• Ileum
• Appendix
• Transverse colon
• Sigmoid colon

Major Secondary Retroperitoneal Organs : (loss of mesentery during development)

• Duodenum 2 & 3 parts
• Head ,neck, & body of pancreas
• Ascending colon
• Descending colon
• Upper rectum

Major Primary Retroperitoneal Organs : (never had a mesentery)

• Kidneys
• Adrenal glands
• Ureters
• Aorta
• Inferior vena cava
• Lower rectum 
• Anal canal

Germ layer Derivatives Ectoderm (Neural crest)

Neural crest

• Adrenal Medulla

• Ganglia :

-Sensory-pseudounipolar neurons
-Autonomic-postganglionic neurons

• Pigment cells

• Schwann cells

• Meninges- Pia and arachnoid mater

• Pharyngeal arch cartilage

• Odontoblasts

• Parafollicular (C) cells

• Aorticopulmonary septum

• Endocardial cushions 

Difference between Esophageal varices and Mallory-Weiss syndrome

• Laceration at the GE junction due to severe prolonged vomiting (MW syndrome)

• Dilated submucosal veins in the lower third of the esophagus ,usually secondary to portal hypertension (EV)

• Most Common Cause : alcoholism in (MW syndrome) , Cirrhosis in (EV)

• Presentation : Mild hematemesis in (MW syndrome) , Massive hematemesis when ruptured in (EV) 

• Complication : Boerhaave syndrome (esophageal rupture) in (MW syndrome) , Potentially fatal hemorrhage in (EV) 

both can possibly lead to death in alcoholics.

Colon polyps types description and their progression to malignancy

• Type : Hyperplastic polyp 

Description
Sawtooth glandular epithelium with proliferation of globet and columnar epithelial cells

Progression to Malignancy
No

• Type: Tubular adenoma

Description
Pedunculated

Progression to Malignancy
Low (4%)

• Type : Tubulovillous adenoma

Description
Combines both

Progression to Malignancy
Intermediated

• Type : Villous adenoma

Description
Sessile

Progression to Malignancy
High (30%)

• Type : Famililal Adenomatous Polyposis

Description
Autosomal Dominant Thousands of Colonic adenomatous polyps

Progression to Malignancy
100% (by 40 year)

• Type : Gardner syndrome

Description
Autosomal Dominant Associated with desmoid tumors

Progression to Malignancy
~ 100%

• Type : Turcot Syndrome

Description
Associated with CNS tumors(gliomas)

Progression to Malignancy
Highly

• Type : Peutz-Jeghers Syndrome

Description
Autosomal Dominant Hamartomas. Melanin Pigmentation of the buccal mucosa

Progression to Malignancy
No

Figure : Colonic adenocarcinoma of cecum

• Colon Cancer 

HNPCC (lynch Syndrome)

• Autosomal Dominant
• Mutation of DNA nucleotide mismatch repair gene
• Increased risk of endometrial and ovarian carcinoma