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Anatomy

Head and Neck

Question 58 of 180

The levator palpebrae superioris muscle is innervated by which of the following nerves:

Answer:

The levator palpebrae superioris muscle originates from the roof of the orbit and inserts into the superior tarsus, is innervated by the oculomotor nerve and raises the upper eyelid.

The upper and lower eyelids are anterior structures that protect the eyeball when closed. The space between the eyelids is the palpebral fissure.

Layers

The layers of the eyelids consist of (from anterior to posterior)

  • skin
  • subcutaneous tissue
  • voluntary muscle
  • the orbital septum (an extension of periosteum which attaches to the tarsus)
  • the tarsus (a plate of dense connective tissue which provide the major support for the eyelid)
  • conjunctiva (a thin membrane, composed primarily of stratified squamous epithelium, which covers the posterior surface of each eyelid before reflecting onto the sclera of the eyeball).

The upper and lower eyelids are basically the same, except for the addition of two muscles in the upper eyelid, the levator palpebrae superioris and the superior tarsal muscle, and the inferior tarsal muscle in the lower eyelid.

By Henry Vandyke Carter [Public domain], via Wikimedia Commons

Layers of the Eyelids. (Image by Henry Vandyke Carter [Public domain], via Wikimedia Commons)

Muscles

The orbicularis oculi muscle is innervated by the facial nerve and closes the eyelids. Loss of function of the orbicularis oculi causes an inability to close the eyelids tightly and a drooping of the lower eyelid (ectropion) resulting in spillage of tears. This leads to drying of the cornea, with subsequent ulceration and secondary infection.

The levator palpebrae superioris muscle originates from the roof of the orbit and inserts into the superior tarsus. It is innervated by the oculomotor nerve and acts to raise the upper eyelid. Loss of function of the levator palpebrae superioris muscle results in a complete ptosis.

The superior tarsal muscle is a collection of smooth muscle fibres in companion with the levator palpebrae superioris, innervated by postganglionic sympathetic fibres from the superior cervical ganglion, which helps to maintain upper eyelid opening. Loss of function of the superior tarsal muscle results in a partial ptosis.

Muscles of the Eyelids. (Image by Henry Vandyke Carter [Public domain], via Wikimedia Commons)

Innervation

The sensory innervation of the eyelids and conjunctiva is from:

  • the supraorbital nerve (ophthalmic nerve)
  • the supratrochlear nerve (ophthalmic nerve)
  • the infratrochlear nerve (ophthalmic nerve)
  • lacrimal branches (ophthalmic nerve)
  • the infraorbital nerve (maxillary nerve)

By Patrick J. Lynch, medical illustrator (Patrick J. Lynch, medical illustrator) [CC BY 2.5], via Wikimedia Commons

Cutaneous Innervation of the Head. (Image by Patrick J. Lynch, medical illustrator [CC BY 2.5], via Wikimedia Commons)

Glands

Embedded in the tarsal plates are modified sebaceous tarsal glands (Meibomian glands) which empty an oily substance onto the free margin of each eyelid that increases the viscosity of tears and decreases the rate of evaporation of tears from the surface of the eyeball.

Blockage and inflammation of a tarsal gland is a chalazion and is on the inner surface of the eyelid. External sebaceous and sweat glands associated with the eyelash follicles may also become blocked and inflamed causing a stye on the edge of the eyelid.

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  • Biochemistry
  • Blood Gases
  • Haematology
Biochemistry Normal Value
Sodium 135 – 145 mmol/l
Potassium 3.0 – 4.5 mmol/l
Urea 2.5 – 7.5 mmol/l
Glucose 3.5 – 5.0 mmol/l
Creatinine 35 – 135 μmol/l
Alanine Aminotransferase (ALT) 5 – 35 U/l
Gamma-glutamyl Transferase (GGT) < 65 U/l
Alkaline Phosphatase (ALP) 30 – 135 U/l
Aspartate Aminotransferase (AST) < 40 U/l
Total Protein 60 – 80 g/l
Albumin 35 – 50 g/l
Globulin 2.4 – 3.5 g/dl
Amylase < 70 U/l
Total Bilirubin 3 – 17 μmol/l
Calcium 2.1 – 2.5 mmol/l
Chloride 95 – 105 mmol/l
Phosphate 0.8 – 1.4 mmol/l
Haematology Normal Value
Haemoglobin 11.5 – 16.6 g/dl
White Blood Cells 4.0 – 11.0 x 109/l
Platelets 150 – 450 x 109/l
MCV 80 – 96 fl
MCHC 32 – 36 g/dl
Neutrophils 2.0 – 7.5 x 109/l
Lymphocytes 1.5 – 4.0 x 109/l
Monocytes 0.3 – 1.0 x 109/l
Eosinophils 0.1 – 0.5 x 109/l
Basophils < 0.2 x 109/l
Reticulocytes < 2%
Haematocrit 0.35 – 0.49
Red Cell Distribution Width 11 – 15%
Blood Gases Normal Value
pH 7.35 – 7.45
pO2 11 – 14 kPa
pCO2 4.5 – 6.0 kPa
Base Excess -2 – +2 mmol/l
Bicarbonate 24 – 30 mmol/l
Lactate < 2 mmol/l

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