Anatomical Basis of Dentistry: Intro to Musculoskeletal system

Chapter 1.3, 1.4. 1.5

-O-

Cartilage

• Supporting connective tissue

• Consists of cells (chondroblast chondrocytes) contained within a ground substance of a rigid gel

• No neurovascular element within nutrients diffuse through ground substance

• Fetal skeleton is mostly cartilage, replaced by bone subsequently

• Growth: internal growth (from inside) & appositional growth (from surface)

Cartilage: types

• Hyaline (hyalos = glass). Gross: bluish white, translucent. Found in fetal skeleton, articular cartilage, costal cartilage, respiratory cartilages, auditory cartilages

• Elastic cartilage. Gross: yellowish because of the elastin fibers. Found in the external ear and in the epiglottis

• Fibrocartilage: more collagen fibers. It is found in tendon insertions and the intervertebral discs

Bone

• Living tissue

• Consisting of cells (osteoblasts osteocytes) within an organic framework (matrix)

• Bone matrix is calcified (unlike cartilages)

• Calcification prevents diffusion of nutrients direct vascular supply is needed

• Growth: internal growth not possible only appositional through periosteum

Bone: functions

• Support: rigid framework of the body

• Movement: act as levers for muscles

• Protection: the brain and thoracic viscera are protected

• Hemopoiesis: within the marrow space of bone

• Storage: for calcium and phosphorus

Bone classification

By Region:

• Axial: skull-vertebrae-costae-sternum

• Appendicular: bones of the upper and lower limbs

By shape:

• Long bones: • hollow tubes/shafts/diaphysis capped at both ends by epiphysis

• Cross section: (1) outer compact layer, (2) inner cancellous/spongy layer of trabeculated bone, (3) marrow space containing blood-forming tissue or fats

• Blood supply: (1) nutrient arteries, (2) periosteal arteries, (3) epiphyseal arteries

By shape (continued):

• Short bones: cuboidal not tubular carpal bones, tarsal bones

• Flat bones: thin and flat, sandwich of 2 layers of compact bone and a cancellous layer (diploe) in between skull, scapula

• Irregular bones: bones that fit none of the previous description maxilla, lacrimal, etc

• Sesamoid bones: grow within a tendon patella (largest sesamoid)

Bone: surface features

• The surface of individual bones is marked by features that reflect• Attachment of muscles and ligaments raised areas

• Passage of nerves and vessels openings, depressions

• Articulation with other bones joint surface, either raised or depressed

• Elevations: condyle, epicondyle, process, plate, tubercle, tuberosity, trochanter, malleus, crest, linea, spine

• Depressions: fossa, sulcus, notch/incisura

• Spaces: foramen, canal, fissure

Joints

• Articulation or union between two or more bones

• By the degree of movement:• Synarthroidal: NO movement

• Amphiarthroidal: SOME movement

• Diarthroidal: FREE movement

• By the joint tissue: fibrous connective tissue, cartilage, combo connective + cartilage, combo cartilage + joint cavity

Fibrous joints

• 3 types: Suture, Syndesmosis, gomphosis

• Sutures: • only between bones of the skull. Fetal amphiarthrodial adult synarthodial

• Squamous, serrated, denticulate

• Syndesmosis: amphiarthrodial, united by fibrous interosseous membrane

• Gomphosis: peg-and-socket articulation between the roots of the teeth and the alveolar processes, united by the fibrous periodontal ligament. Normally NO mobility.

cartilaginous joints

Primary cartilaginous joints (synchondroses)

• Develop between 2 bones od endochondral origin

• Solid plate of hyaline cartilage between apposing surfaces

• E.g. sphenooccipital synchondrosis

Secondary cartilaginous joints (symphysis)

• Amphiarthordial

• Apposing bony surfaces are covered with cartilage but separated by fibrous/fibrocartilage

• E.g. Intervertebral discs, symphysis pubis, symphysis menti

Synovial joints

• Freely movable (diarhtrodial)

Characteristic:

• Articular cartilage: hyaline, fibrocartilage. No blood vessels

• Joint cavity: between the articular surfaces, contains thin synovial fluid

• Capsular ligament: surrounds the joint,

• synovial membrane: lining the internal surface of the capsule, but not the articular cartilage

• Disc: not always present, if present it divides the joint cavity to compartments in Temporomandibular joint

Synovial joints: Axes

• Multiaxial joints: 3 planes• Ball-and-socket joint

• Saddle/ellipsoid joint

• Biaxial joints: 2 planes (no rotation)• Condyloid joint

• Uniaxial joints: 1 plane• Plane joint

• Hinge joint (ginglymus)

• Pivot joint

Skeletal Muscles

• Skeletal attached to bones, span joints, move one bone in relation to another

• Mostly under voluntary control

• Striated from the histological sections

Skeletal muscles: nomenclature

• Indicating the shape: (e.g. deltoid, trapezius)

• Indicating the number of origins (e.g. triceps, biceps)

• Indicating the location (e.g. temporalis, brachialis)

• Indicating the number of bellies (e.g. digastricus)

• Indicating the function: (e.g. levator veli palatini, tensor tympani)

• Indicating the origin and insertion (e.g. thyrohyoid)

Skeletal muscles: parts

Fleshy portion/Venter

• Contains muscle fibers

• Muscle fibers/cells-fasiculus-muscles-group of muscles/compartment

• Endomysium-perimysium-epimysium-intermuscular septa

Tendinous portion: attaching part of the muscle

• Cylindrical tendons

• Linear tendon

• Aponeurosis

• Common tendon

Skeletal muscles: origin and insertion

• Origin: proximal end of a muscle

• Insertion: the distal end of a muscle

• In movements, the insertion moves toward the stationary origin as the muscle contracts

• Technically, origins and insertions can be interchanged

Skeletal muscles: architecture

• The arrangement of the muscle fiber bundles/fasciculi

• Parallel and converging fibers (no interruption of the fasciculi from origin to insertion for the range of movement): • rectangular muscles, triangular muscles, fusiform muscles

• Pennate muscles (central tendon with obliquely arranged muscle bundles for power): • unipennate, bipennate, multipennate

• Sphincter muscles (circular muscles encircle openings, where contraction closes the opening)

Skeletal muscles: Actions

• Types of contraction: • Isotonic (same tone) produce actual movement• Isometric (same length) no movement

• Action of muscle groups• Prime movers: Muscles that are controlled by pyramidal system and are used

to initiate a particular movement• Antagonist: muscles that produce movement in the opposite direction of the

prime movers. • Synergists: muscles that are controlled by extrapyramidal system to refine the

movement of the prime movers• Fixators: indirectly involved in the movement by stabilizing the body.