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NEET MDS Lessons
Anatomy

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

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.

 

The Hard Palate

  • The anterior bony part of the palate is formed by the palatine process of the maxillae and the horizontal plates of the palatine bones.
  • Anteriorly and laterally, the hard palate is bounded by the alveolar processes and the gingivae.
  • Posteriorly, the hard palate is continuous with the soft palate.
  • The incisive foramen is the mouth of the incisive canal.
  • This foramen is located posterior to the maxillary central incisor teeth.
  • This foramen is the common opening for the right and left incisive canals.
  • The incisive canal and foramen transmit the nasopalatine nerve and the terminal branches of the sphenopalatine artery.
  • Medial to the third molar tooth, the greater palatine foramen pierces the lateral border of the bony palate.
  • The greater palatine vessels and nerve emerge from this foramen and run anteriorly into two grooves on the palate.
  • The lesser palatine foramen transmits the lesser palatine nerve and vessels.
  • This runs to the soft palate and adjacent structures.

  • Cartilage model is covered with perichondrium that is converted to periosteum

  • Diaphysis-central shaft
  • Epiphysis-located at either end of the diaphysis
  • Growth in length of the bone is provided by the emetaphyseal plate located between the epiphyseal cartilage and the diaphysis
  • Blood capillaries and the mesenchymal cells infiltrate the spaces left by the destroyed chondrocytes

  • Osteoblasts are derived from the undifferentiated cells; form an osseous matrix in the cartilage
  • Bone appears at the site where there was cartilage

      Microscopic structure

  • Compact bone is found on the exterior of all bones; canceIlous bone is found in the interior
  • Surface of compact bone is covered by periosteum that is attached by Sharpey's fibers
  • Blood vessels enter the periosteum via Volkmann's canals and then enter the haversian canals that are formed by the canaliculi and lacunae
  •  

  • Marrow
    • FiIls spaces of spongy bone
    • Contains blood vessels and blood ceIls in various stages of development
    • Types
  • Red bone marrow
    • Formation of red blood ceIls (RBCs) and some white blood cells (WBCs) in this location
    • Predominate type of marrow in newborn
    • Found in spongy bone of adults (sternum, ribs, vertebrae, and proximal epiphyses of long bones)
  •  Yellow bone marrow
    • Fatty marrow
    • Generally replaces red bone marrow in the adult, except in areas mentioned above
  •  
  • Ossification is completed as the proximal epiphysis joins with the diaphysis between the twentieth and twenty-fifth year

Innervation of the Pharynx

  • The motor and most of the sensory supply of the pharynx is derived from the pharyngeal plexus of nerves on the surface of the pharynx.
  • The plexus is formed by pharyngeal branches of the vagus (CN X) and glossopharyngeal (CN IX) nerves, and by sympathetic branches for the superior cervical ganglion.
  • The motor fibres in the pharyngeal plexus are derived from the cranial root of accessory nerve (CN XI), and are carried by the vagus nerve to all muscles of the pharynx and soft palate.
  • The exceptions are stylopharyngeus (supplied by CN IX) and the tensor veli palatini (supplied by CN V3).

The Muscles of Facial Expression

  • These lie in the subcutaneous tissue and are attached to the skin of the face.
  • They enable us to move our skin and change our facial expression. They produce their effects by pulling on the skin but do not move the facial skeleton.
  • These muscles surround the facial orifices and act as sphincters and dilators.
  • All facial muscles receive their innervation from the branches of the facial nerve (CN VII)-temporal, zygomatic, buccal, marginal mandibular, cervical.

Mylohyoid Muscle

  • Origin: Mylohyoid line of the mandible.
  • Insertion: Median raphe and body of the hyoid bone.
  • Nerve Supply: Nerve to mylohyoid (branch of the trigeminal nerve, CN V3).
  • Arterial Supply: Sublingual branch of the lingual artery and submental branch of the facial artery.
  • Action: Elevates the hyoid bone, base of the tongue, and floor of the mouth; depresses the mandible.

  • This is the second cranial nerve (CN II) and is the nerve of sight.

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