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Anatomy - NEETMDS- courses
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Anatomy

Levator Palpebrae Superioris Muscles

  • This is a thin, triangular muscle that elevates the upper eyelid.
  • It is continuously active except during sleeping and when the eye is closing.
  • Origin: roof of orbit, anterior to the optic canal.
  • Insertion: this muscle fans out into a wide aponeurosis that inserts into the skin of the upper eyelid. The inferior part of the aponeurosis contains some smooth muscle fibres that insert into the tarsal plate.
  • Innervation: the superior fibres are innervated by the oculomotor nerve (CN III), and the smooth muscle component is innervated by fibres of the cervical sympathetic trunk and the internal carotid plexus.

 

Illnesses involving the Levator Palpebrae Superioris

  • In third nerve palsy, the upper eyelid droops (ptosis) and cannot be raised voluntarily.
  • This results from damage to the oculomotor nerve (CN III), which supplies this muscle.
  • If the cervical sympathetic trunk is interrupted, the smooth muscle component of the levator palpebrae superioris is paralysed and also causes ptosis.
  • This is part of Horner's syndrome.

 

The Rectus Muscles

 

  • There are four rectus muscles (L. rectus, straight), superior, inferior, medial and lateral.
  • These arise from a tough tendinous cuff, called the common tendinous ring, which surrounds the optic canal and the junction of the superior and inferior orbital fissures.
  • From their common origin, these muscles run anteriorly, close to the walls of the orbit, and attach to the eyeball just posterior to the sclerocorneal junction.
  • The medial and lateral rectus muscles attach to the medial and lateral sides of the eyeball respectively, on the horizontal axis.
  • However, the superior rectus attaches to the anterosuperior aspect of the medial side of the eyeball while the inferior rectus attaches to the anteroinferior aspect of the medial side of the eye.

 

The Oblique Muscles

The Superior Oblique Muscle

  • This muscle arises from the body of the sphenoid bone, superomedial to the common tendinous ring.
  • It passes anteriorly, superior and medial to the superior and medial rectus muscles.
  • It ends as a round tendon that runs through a pulley-like loop called the trochlea (L. pulley).
  • After passing though the trochlea, the tendon of the superior oblique turns posterolaterally and inserts into the sclera at the posterosuperior aspect of the lateral side of the eyeball.

 

The Inferior Oblique Muscle

  • This muscle arises from the maxilla in the floor of the orbit.
  • It passes laterally and posteriorly, inferior to the inferior rectus muscle.
  • It inserts into the sclera at the posteroinferior aspect of the lateral side of the eyeball.

  • Articulations

    Classified according to their structure, composition,and movability
    •    Fibrous joints-surfaces of bones almost in direct contact with limited movement
        o    Syndesmosis-two bones united by interosseous ligaments
        o    Sutures-serrated margins of bones united by a thin layer of fibrous tissue
        o    Gomphosis-insertion of a cone-shaped process into a socket

    •    Cartilaginous joints-no joint cavity and contiguous bones united by cartilage
        o    Synchondrosis-ends of two bones approximated by hyaline cartilage
        o    Symphyses-approximating bone surfaces connected by fibrocartilage

    •    Synovial joints-approximating bone surfaces covered with cartilage; may be separated by a disk; attached by ligaments 
        o    Hinge-permits motion in one plane only
        o    Pivot-permits rotary movement in which a ring rotates around a central axis
        o    Saddle-opposing surfaces are convexconcave. allowing great freedom of motion
        o    Ball and socket - capable of movement in an infinite number of axes; rounded head of one bone moves in a cuplike cavity of the approximating bone

    Bursae
    •    Sacs filled with synovial fluid that are present where tendons rub against bone or where skjn rubs across bone
    •    Some bursae communicate with a joint cavity 
    •    Prominent bursae found at the elbow. hip, and knee'

    Movements
    •    Gliding
        o    Simplest kind of motion in a joint
        o    Movement on a joint that does not involve any angular or rotary motions
    •    Flexion-decreases the angle formed by the union of two bones
    •    Extension-increases the angle formed by the union of two bones
    •    Abduction-occurs by moving part of the appendicular skeleton away from the median plane of the body
    •    Adduction-occurs by moving part of the appendicular skeleton toward the median plane of the body
    •    Circumduction
        o    Occurs in ball-and-socket joints
        o    Circumscribes the conic space of one bone by the other bone
    •    Rotation-turning on an axis without being displaced from that axis
     

The Palate

  • The palate forms the arched roof of the mouth and the floor of the nasal cavities.
  • The palate consists of two regions: the anterior 2/3 or bony part, called the hard palate, and the mobile posterior 1/3 or fibromuscular part, known as the soft palate.

Intrinsic Muscles of the Tongue

The Superior Longitudinal Muscle of the Tongue

  • The muscle forms a thin layer deep to the mucous membrane on the dorsum of the tongue, running from its tip to its root.
  • It arises from the submucosal fibrous layer and the lingual septum and inserts mainly into the mucous membrane.
  • This muscle curls the tip and sides of the tongue superiorly, making the dorsum of the tongue concave.

 

The Inferior Longitudinal Muscle of the Tongue

  • This muscle consists of a narrow band close to the inferior surface of the tongue.
  • It extends from the tip to the root of the tongue.
  • Some of its fibres attach to the hyoid bone.
  • This muscle curls the tip of the tongue inferiorly, making the dorsum of the tongue convex.

 

The Transverse Muscle of the Tongue

  • This muscle lies deep to the superior longitudinal muscle.
  • It arises from the fibrous lingual septum and runs lateral to its right and left margins.
  • Its fibres are inserted into the submucosal fibrous tissue.
  • The transverse muscle narrows and increases the height of the tongue.

 

The Vertical Muscle of the Tongue

  • This muscle runs inferolaterally from the dorsum of the tongue.
  • It flattens and broadens the tongue.
  • Acting with the transverse muscle, it increases the length of the tongue.

Muscles Around the Nose

The Nasalis Muscle

  • This muscle consists of a transverse (compressor naris) and alar (dilator naris) parts.
  • It is supplied by the buccal branch of the facial nerve.

The Lips

  • These are mobile muscular folds that surround the mouth, the entrance of the oral cavity.
  • The lips (L. labia) are covered externally by skin and internally by mucous membrane.
  • In between these are layers of muscles, especially the orbicularis oris muscle.
  • The upper and lower lips are attached to the gingivae in the median plane by raised folds of mucous membrane, called the labial frenula.

Sensory Nerves of the Lips

  • The sensory nerves of the upper and lower lips are from the infraorbital and mental nerves, which are branches of the maxillary (CN V2) and mandibular (CN V3) nerves.

Pharyngeal Arch

Arch Artery

Cranial Nerve

Skeletal elements

Muscles

1

Terminal Branch of maxillary artery

Maxillary and mandibular division of trigemenial (V)

Derived from arch cartilages (originating from neural crest):

From maxillary cartilages:

Alispenoid, incus

From mandibular:

Mackel’s cartilage, malleus

 

Upper portion of external ear (auricle) is derived from dorsal aspect of 1st pharyngeal arch.

 

Derived by direct ossification from arch dermal mesenchyme:

Maxilla, zygomatic, squamous portion of temporal bone, mandible

 

Muscles of mastication (temporalis, masseter, and pterygoids), mylohyoid, anterior belly of digastric, tensor tympani, tensor veli palatini (originate from cranial somitomere 4)

2

Stapedius artery (embryologic) and cortiotympanic artery (adult)

Facial nerve (VII)

Stapes, styloid process, stylohyoid ligament, lesser horns and upper rim of hyoid (derived from the second arch cartilage; originate from neural crest).

 

Lower portion of external ear (auricle) is derived from 2nd pharyngeal arch.

Muscles of facial expression (orbicularis oculi, orbicularis oris, auricularis, platysma, fronto-ooccipitalis, buccinator), posterior belly of digastric, stylohyoid, stapedius (originate from cranial somitomere 6)

3

Common carotid artery, most of internal carotid

Glossopharyngeal (IX)

Lower rim and greater horn of hyoid (derived from the third arch cartilage; originate from neural crest cells)

Sytlopharyngeus (originate from cranial somitomere 7)

4

Left: Arch of aorta;

Right: Right subclavian artery;

Original sprouts of pulmonary arteries

Superior laryngeal branch of vagus (X)

Laryngeal cartilages (Derived from the 4th arch cartilage, originate from lateral plate mesoderm)

Constrictors of pharynx, cricothyroid, levator veli palatine (originate from occipital somites 2-4)

6

Ductus arteriosus; roots of definitive pulmonary arteries

Recurrent laryngeal branch of vagus (X)

Laryngeal cartilages (derived from the 6th-arch cartilage; originate from lateral plate mesoderm)

Intrinsic muscles of larynx (originate from occipital somites 1 and 2)
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