Talk to us?

Anatomy - NEETMDS- courses
NEET MDS Lessons
Anatomy

The Soft Palate

  • This is the posterior curtain-like part, and has no bony support. It does, however, contain a membranous aponeurosis.
  • The soft palate, or velum palatinum (L. velum, veil), is a movable, fibromuscular fold that is attached to the posterior edge of the hard palate.
  • It extends posteroinferiorly to a curved free margin from which hangs a conical process, the uvula (L. uva, grape).
  • The soft palate separates the nasopharynx superiorly and the oropharynx inferiorly.
  • During swallowing the soft palate moves posteriorly against the wall of the pharynx, preventing the regurgitation of food into the nasal cavity.
  • Laterally, the soft palate is continuous with the wall of the pharynx and is joined to the tongue and pharynx by the palatoglossal and palatopharyngeal folds.
  • The soft palate is strengthened by the palatine aponeurosis, formed by the expanded tendon of the tensor veli palatini muscle.
  • This aponeurosis attaches to the posterior margin of the hard palate.

-> This is a wedge-shaped bone (G. sphen, wedge) is located anteriorly to the temporal bones.
-> It is a key bone in the cranium because it articulates with eight bones (frontal, parietal, temporal, occipital, vomer, zygomatic, palatine, and ethmoid).
-> It main parts are the body and the greater and lesser wings, which spread laterally from the body.
-> The superior surface of its body is shaped like a Turkish saddle (L. sella, a saddle); hence its name sella turcica.
-> It forms the hypophyseal fossa which contains the hypophysis cerebri or pituitary gland.
-> The sella turcica is bounded posteriorly by the dorsum sellae, a square plate of bone that projects superiorly and has a posterior clinoid process on each side.
-> Inside the body of the sphenoid bone, there are right and left sphenoid sinuses. The floor of the sella turcica forms the roof of these paranasal sinuses.
-> Studies of the sella turcica and hypophyseal fossa in radiographs or by other imaging techniques are important because they may reflect pathological changes such as a pituitary tumour or an aneurysm of the internal carotid artery. Decalcification of the dorsum sellae is one of the signs of a generalised increase in intracranial pressure.

 

The Submandibular Glands

  • Each of these U-shaped salivary glands is about the size of a thumb and lies along the body of the mandible.
  • It is partly superior and partly inferior to the posterior 1/2 of the base of the mandible.
  • It is partly superficial and partly deep to the mylohyoid muscle.
  • The submandibular duct arises from the portion of the gland that lies between the mylohyoid and hyoglossus muscle.
  • The duct passes deep and then superficial to the lingual nerve.
  • It opens by one to three orifices on a small sublingual papilla beside the lingual frenulum.
  • The submandibular gland is supplied by parasympathetic, secretomotor fibres from the submandibular ganglion (preganglionic fibres from the chorda tympani via the lingual nerve).

Intramembranous ossification

  • Flat bones develop in this way (bones of the skull)
  • This type of bone development takes place in mesenchymal tissue
  • Mesenchymal cells condense to form a primary ossification centre (blastema)
  • Some of the condensed mesenchymal cells change to osteoprogenitor cells
  • Osteoprogenitor cells change into osteoblasts which start to deposit bone
  • As the osteoblasts deposit bone some of them become trapped in lacunae in the bone and then change into osteocytes
  • Osteoblasts lie on the surface of the newly formed bone
  • As more and more bone is deposited more and more osteocytes are formed from mesenchymal cells
  • The bone that is formed is called a spicule
  • This process takes place in many places simultaneously
  • The spicules fuse to form trabeculae
  • Blood vessels grow into the spaces between the trabeculae
  • Mesenchymal cells in the spaces give rise to hemopoetic tissue
  • This type of bone development forms the first phase in endochondral development
  • It is also responsible for the growth of short bones and the thickening of long bones

  • 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 Masseter Muscle

  • This is a quadrangular muscle that covers the lateral aspect of the ramus and the coronoid process of the mandible.
  • Origin: inferior border and medial surface of zygomatic arch.
  • Insertion: lateral surface of ramus of mandible and its coronoid process.
  • Innervation: mandibular nerve via masseteric nerve that enters its deep surface.
  • It elevates and protrudes the mandible, closes the jaws and the deep fibres retrude it.

A. Anatomic position-erect body position with the arms at the sides and the palms  upward

B. Plane or section

1. Definition-imaginary flat surface formed by an extension through an axis

2. Median plane-a vertical plane. that divides a body into right and left halves

3. Sagittal plane

  • Any plane parallel to the median plane
  • Divides the body into right and left portions

 

4. Frontal plane

  • Vertical plane that forms at right angles to the sagittal plane
  • Divides the body into anterior and posterior sections
  • Synonymous with the term coronal plane

 

5. Transverse plane

  • Horizontal plane that forms at right angles to the sagittal and frontal planes
  • Divides the body into upper and lower portions
  • Synonymous with the term horizontal plane

 

 

C. Relative positions

1. Anterior

  • Nearest the abdominal surface and the front of the body
  • Synonymous with the term ventral
  • In referring to hands and forearms, the terms palmar and Volar are used

2. Posterior

  • Back of the body
  • Synonymous with the term dorsal

3. Superior

  • Upper or higher
  • Synonymous with the term cranial (head)

4. Inferior

  • Below or lower
  • Synonymous with the term caudal (tail)
  • In referring to the top of the foot and the sole of the foot. the terms dorsal and plantar are used respectively

 

5. Medial-near to the median plane

6. Lateral-farther away from the median plane

7. Proximal-near the source or attachment

8. Distal-away from the source or. attachment

9. Superficial-near the surface

10. Deep-away from the surface

11. Afferent-conducting toward a structure

12. Efferent-conducting away from a structure

Explore by Exams