NEET MDS Lessons
Anatomy
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Part of the axial skeleton; strong, flexible rod
Supports the head
Gives base to the ribs
Encloses the spinal cord
o Vertebrae
Consists of 34 bones composing the spinal column
• Cervical-7 bones
• Thoracic-12 bones
• Lumbar-5 bones
• Sacral- 5 bones.
• Coccygeal-4 to 5 bonesIn the adult the vertebrae of the sacral and coccygeal regions are united into two bones, the sacrum and me coccyx
o Curvatures-from a lateraI view there are four curves, alternately convex and concave ventrally
Two convex curves are the cervical and lumbar
Two concave curves are the thoracic and sacralo Vertebra morphology
Each vertebra differs in size and shape hut has similar components
Body-central mass of bone
• Weight bearing
• Fonns anterior part of the vertebra
• Encloses the vertebral foramen
Pedicles of the arch-two thick columns that extend backward from the body to meet with the laminae of the neural arch -
Process (7)
• One spinous, two transverse, two superior articular, and two inferior articular
o Spinous process extends backward from the point of the union of thetwo laminae
o Transverse processes project laterally at either side from the junction of the lamina and the pedicle
o Articular processes arise near the junction of the pedicle and the lamina- superior processes project upward:inferior processes project downward
• Surfaces of the processes are smootho Inferior articular processes of the vertebra fit into the superior articular processes below
o Form true joints, but the contacts established serve to restrict movementDistinguishing features
Cervical region- triangular shape
• All have foramina in the transverse process upper six transmit the vertebral artery
• Spinous processes are short
o C3 to C5 are bifurcated
o C7 is long-prominence felt at the back of the neck
• Have small bodies (except for C1 vertebra)
• C1 vertebra (atlas)
o No body
o Anterior and posterior arch and two lateral masses
o Superiorarticular processes articulate with the condyles of the occipital bone
• C2 vertebra (axis)-process on the upper surface of the body (dens) forms a pivot about which the axis rotatesThoracic region
• Presence of facets for articulation with the ribs (distinguishing feature)
• Processes are larger and heavier than those of the cervical region
• Spinous process is directed downward at a sharp angle
• Circular vertebral foramenLumbar region
• Large and heavy bodies
• Four transverse lines separate the bodies of the vertebrae on the pelvic surface
• Triangular shape-fitted between the halves of the pelvis
• Four pairs of dorsal sacral foramina communicate with four pairs of pelvic sacral foraminaSacral vertebrae
• Five (sometimes six) vertebrae are fused in the adult to form the sacrum
• The sacrum articulates above with L5, laterally with the hip bones, and inferiorly with the coccyx.
• It has a roughly triangular appearance with a pelvic and dorsal surface, a lateral mass on each side, and a base and apex.
• An anesthetic for the spinal nerves may be injected extradurally through the sacral hiatus (caudal analgesia)
• The sacral canal (which contains the dura, cauda equina, and filum terminale) extends from the base to the sacral hiatus.
• The apex of the sacrum may be fused with the coccyx.
Coccygeal vertebrae• Four to five modular pieces fused together
• Triangular shape with the base above and the apex belowF Defects
• Lordosis-exaggerated lumbar concavity
• Scoliosis-lateral curvature of any region
• Kyphosis-exaggerated convexity in the thoracic region
Muscles acting on the Temporomandibular Joint
- Movements of the temporomandibular joint are chiefly from the action of the muscles of mastication.
- The temporalis, masseter, and medial pterygoid muscles produce biting movements.
- The lateral pterygoid muscles protrude the mandible with the help from the medial pterygoid muscles and retruded largely by the posterior fibres of the temporalis muscle.
- Gravity is sufficient to depress the mandible, but if there is resistance, the lateral pterygoid, suprahyoid and infrahyoid, mylohyoid and anterior digastric muscles are activated.
| Actions | Muscles | |||
| Depression (Open mouth) |
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| Elevation (Close mouth) |
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| Protrusion (Protrude chin) |
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| Retrusion (Retrude chin) |
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| Side-to-side movements (grinding and chewing) |
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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 boneBursae
• 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
- U-shaped bone
- Body
- Greater horn
- Lesser horn
- Suspended by ligaments from the styloid process
The Medial Wall of the Orbit
- This wall is paper-thin and is formed by the orbital lamina or lamina papyracea of the ethmoid bone, along with contributions from the frontal, lacrimal, and sphenoid bones (L. papyraceus, "made of papyrus" or parchment paper).
- There is a vertical lacrimal groove in the medial wall, which is formed anteriorly by the maxilla and posteriorly by the lacrimal bone.
- It forms a fossa for the lacrimal sac and the adjacent part of the nasolacrimal duct.
- Along the suture between the ethmoid and frontal bones are two small foramina; the anterior and posterior ethmoidal foramina.
- These transmit nerves and vessels of the same name.
Appendicular Skeleton
Upper extremity
• Shoulder-clavicle and scapula
Clavicle
Articulates with the manubrium at the sternal end
Articulates with the scapula at the lateral end
Slender S-shaped bone that extends horizontally across the upper part of the thorax
Scapula
Triangular bone with the base upward and the apex downward
Lateral aspect contains the glenoid cavity that articulates with the head of the humerus
Spine extends across the upper part of the posterior surface; expands laterally and
forms the acromion (forms point of shoulder)
Coracoid process projects anteriorly from the upper part of the neck of the scapula
Arm (humerus)
Consists of a shaft (diaphysis) and two ends (epiphyses)
Proximal end has a head that articulates with the glenoid fossa of the scapula
Greater and lesser tubercles lie below the head
Intertubercular groove is located between them; long tendon of the biceps attaches here
Surgical neck is located below the tubercles
o Radial groove runs obliquely on the posterior surface; radial nerve is located here
o Deltoid muscles attaches in a V-shaped area in the middle of the shaft. called the deltoid tuberosity
Distal end has two projections. the medial and lateral epicondyles
Capitulum-articulates with the radius
Trochlea-articulates with the ulqa
Forearm
Radius
Lateral bone of the forearm
Radial tuberosity is located below the head on the medial side
Distal end is broad for articulation with the wrist: has a styloid process on its lateral side
Ulna
Medial side of the forearm
Conspicuous part of the elbow joint (olecranon)
Curved surface that articulates with the trochlea of the humerus is the trochlearnotch
Lateral ide is concave (radial notch); articulates with the head of the radius Distal end contains the styloid process
Distal end contains the styloid process
Hand
Carpal bones (8)
Aranged in two rows of four
Scaphoid. lunate. triquetral. and pisiform proximal row); trapezium. trapezoid.
capitate. and hamate (distal row)
Metacarpal bones (5)
Framework of the hand
Numbered 1 to 5 beginning on the lateral side
Phalanges (14)
Fingers
Three phalanges in each finger; two phalanges in the thumb
Ligaments of the Joint
- The fibrous capsule is thickened laterally to form the lateral (temporomandibular) ligament. It reinforces the lateral part of this capsule.
- The base of this triangular ligament is attached to the zygomatic process of the temporal bone and the articular tubercle.
- Its apex is fixed to the lateral side of the neck of the mandible.
- Two other ligaments connect the mandible to the cranium but neither provides much strength.
- The stylomandibular ligament is a thickened band of deep cervical fascia.
- It runs from the styloid process of the temporal bone to the angle of the mandible and separates the parotid and submandibular salivary glands.
- The sphenomandibular ligament is a long membranous band that lies medial to the joint.
- This ligament runs from the spine of the sphenoid bone to the lingula on the medial aspect of the mandible.