Features of Bones

Projections

An outward extending part or prominence of a bone that serves a site for tendon and ligament attachment.

Articulations

Where two bones come together. The joint.

Depressions

Recessed area of the bone. Often either fits with a projection or allows attachment.

Openings

Open surfaces of bones. Allows passage of nerves, blood, etc.

Crest

Ridgelike projection. Sites where connective tissue attaches muscle to bone. Ex. Hip bone, median sacral.

Epicondyle

Projection superior to condyle. Attaches muscle and connective tissue to bone, providing support to this musculoskeletal system. Ex. Femur, femoral medial and lateral.

Linea/Line

Projection, narrow slightly raised ridge. Allows a muscle to attach to the bone. Ex. Femur, aspera; pectineal

Process

Projection, bony prominence. Allows for muscle attachment. Ex. Vertebra, spinous; acromial; radial styloid

Protuberance

Projection, protruding outgrowth. Attachment for muscles and ligaments. Ex. Skull, external occipital

Ramus

Projection, armlike bar, branch of bone, makes an angle to the rest of the structure. Gives structural support to the rest of the bone. Ex. Mandible and Ischium

Spine

Projection, thornlike, narrow and pointed. Attachment for muscles and ligaments. Ex. Scapula and Ischium

Trochanter

Projection, large rough knob. Attachment for largest muscle groups and most dense connective tissues. Ex. Femur, greater and lesser.

Tubercle

Projection, small knoblike. Connective tissues attach. Ex. Humerous, greater and lesser.

Tuberosity

Projection, small rough elevation. Muscles and connective tissues attach. Ex. Tibial, deltoid, ischial, and radial.

Condyle

Articulation, rounded process. Provides structural support to the
overlying hyaline cartilage. Ex. Femur, Tibia, and Skull.
femoral lateral and medial; tibial lateral and medial; occipital.

Facet

Articulation, nearly flat. Forms a joint with another flat bone or
another facet, together creating a gliding joint. Ex. Vertebra, for flexion and extension of the spine.

Head

Articulation, expanded end. Prominent extension of bone that forms
part of a joint. Ex. Femur and Radius

Neck

Narrow connection between head and rest of bone

Fossa

Depression, shallow basin. Receives another articulating bone or act to support brain structures. Ex. Humerous and Cranium. trochlear; posterior, middle, and anterior cranial.

Fovea

Depression, tiny pit. Allows the attachment of a ligament. Ex. Femur, blank capitis of the femur

Fissure

Opening, slit. Houses nerves and blood vessels. Ex. Skull, superior and inferior orbital. 

Foramen

Opening, hole. Nerves and blood vessels pass through. Ex. Vertebra, magnum; supraorbital; infraorbital; mental.

Meatus

Opening, tubelike passageway. Provides passage and protection to
nerves, vessels, and even sound. Ex. Skull, external acoustic; internal auditory.

Sinus

Opening, cavity. Open chamber for air and mucus to flow through. Ex. Skull, maxillary; ethmoid; sphenoid; frontal.

Groove/sulcus

Narrow depression

Joints

Synonymous with articulations. Point of contact between: Two bones, cartilage and bone, or teeth and bone. Structure determines strength and flexibility.

Classifications

Either structural or functional.

Functional Classification

Based on the degree of movement permitted, either
• Synarthrosis
• Amphiarthrosis
• Diarthrosis

Synarthrosis

Immovable, ex. sutures of the skull

Amphiarthrosis

Slightly moveable, ex. intervertebral joints

Diarthrosis

Freely movable, ex. hip

Structural Classification

Based on the presence/absence of a synovial cavity and the type of connecting tissue.
• Fibrous
• Cartilaginous
• Synovial

Fibrous Joints

Bones are held together by dense connective tissue containing many collagen fibers; found in bones in close contact. 3 types. Overlaps with two types of function- either synarthrosis or amphiarthrosis.

Suture

Fibrous joint, synarthrotic (immovable). Between flat bones of skull. Thin layer of connective tissue (ligament) connects bones

Syndesmosis

Fibrous joint, amphiarthrotic (flexible, may twist). Bones bound by a sheet of dense connective tissue (interosseous membrane) or a bundle of dense connective tissue (interosseous ligament). Lies between tibia and fibula.

Gomphosis

Fibrous joint, synarthrotic (immovable). Cone-shaped bony process in a socket in jawbone. Tooth in jawbone by periodontal ligament.

Cartilaginous joints

Bones are held together by cartilage. 2 types. Overlaps with two types of function- either synarthrosis or amphiarthrosis.

Synchondrosis

Cartilaginous joints, synarthrotic (immovable). Bands of hyaline cartilage unite bones. Some are temporary, such as epiphyseal plate. Between manubrium and the first rib (costal cartilages, permanent)

Symphysis

Cartilaginous joints, amphiarthrotic (limited movement). Pad of fibrocartilage between bones. Articular surfaces covered by hyaline cartilage. Pubic symphysis. Joint between bodies of adjacent vertebrae (intervertebral discs).

Synovial

Most joints. All are diarthrotic. 6 subtypes.

Synovial joint structure

Fibrous membrane outer layer. Synovial membrane inner layer. Secretes synovial fluid into the synovial cavity it surrounds. Articular cartilage covers articular ends of bones.

Four categories of movement

Gliding, Angular, Rotation, Special.

Gliding movement

Simple movements, associated with plane/planar joints. Back-and-forth or side-to-side. Ex. Carpal joints of the wrist, tarsal joints of the ankle, facet joints of the spine.

Angular movements

Increase or decrease in the angle between articulating bones. Flexion, Extension, Hyperextension, Abduction, Adduction, Circumduction

Flexion

Decrease in angle

Extension

Increase in angle

Hyperextension

Extension beyond anatomical position; angular.

Abduction

Movement of a bone away from the midline. Angular.

Adduction

Movement of a bone towards the midline. Angular.

Horizontal Abduction

Movement of a bone away from the midline along the transverse plane. Angular.

Horizontal Adduction

Movement of a bone towards the midline along the transverse plane. Angular.

Circumduction

Movement of the distal end of a part of the body in a circle. Angular. 

Rotation

Bone revolves around its own longitudinal axis

Medial/Internal Rotation

Bone of the limb is turned toward the midline.

Lateral/External Rotation

Bone of the limb is turned away from the midline.

Special movements

Only occur at certain joints.

Elevation

Upward special movement 

Depression

Downward special movement.

Protraction

Special movement forward.

Retraction

Special movement of a protracted back to the anatomical position.

Inversion

Movement of the soles of the feet medially so they face each other.

Eversion

Movement of the soles of the feet laterally so they face away from each other. 

Dorsiflexion

Bending of the foot in the direction of the dorsum (up)

Plantar Flexion

Bending of the foot in the direction of the plantar surface

Supination

Movement of the forearm so that the palm is turned forward 

Pronation

Movement of the forearm so that the palm is turned backward

Opposition

Thumb moves across the palm to touch the fingertips on the same hand 

Planar

Type of synovial joint. Joint surfaces are flat. Gliding movement; back-and-forth and side-to-side. Ex. Between tarsals, between carpals.

Hinge

Type of synovial joint. Convex surface of one bone fits into the concave surface of another. Flexion/Extension. Ex. Elbow, knee, ankle.

Pivot

Type of synovial joint. Round or pointed surface of one bone fits into a ring formed by another bone and ligament. Rotation. Ex. Atlanto-axial joint of the neck, Radioulnar joint of the forearm at the elbow

Condyloid

Type of synovial joint. Oval projection of one bone fits into an oval
cavity of another. Flexion/Extension and Ab/Adduction. Ex. Wrist, Metacarpophalangeal joints (2nd-5th) 

Saddle

Type of synovial joint. Surface of one bone is shaped like a saddle and the other bone fits into the saddle like a rider. Flexion/Extension, Ab/Adduction, and Rotation. Ex. Carpometacarpal joint of the thumb 

Ball-and-Socket

Type of synovial joint. Ball-shaped surface fits into the cuplike depression of another. Flexion/Extension, Ab/Adduction, and Rotation. Ex. Shoulder, Hip

Sprains

Tearing of connective tissue in joint, without bone dislocation.

Bursitis

Inflammation of a bursa, from overuse or stress.

Arthritis

Inflammation, swelling, and pain in a joint.

Rheumatoid arthritis

autoimmune disease.

Osteoarthritis

degenerative, most common type, occurs with aging.

Lyme arthritis

caused by Lyme disease, passed through tick bite.