Human Skeleton: Osteology

• Osteology is the scientific study of the structure and function of bones.

The Human Skeleton

• The human skeleton includes bones such as the Skull, Cervical Vertebra, Clavicle, Scapula, Manubrium, Sternal Body, Rib, Humerus, Xiphoid Process, Thoracic Vertebra, Lumbar Vertebra, Ulna, Radius, Os Coxae, Sacrum, Coccyx, Carpal bone, Metacarpal, Phalanx, Femur, Patella, Tibia, Fibula, Medial Malleolus, Lateral Malleolus, Tarsal Bone, Metatarsal, and Calcaneus.

Axial Skeleton

• The axial skeleton consists of 80 bones that form the body's axis or center
• It includes bones of the head and trunk
• The skull and associated bones = 28
• The Hyoid = 1
• The Sternum = 1
• The Ribs = 24
• The Vertebrae, Sacrum, and Coccyx = 26

Appendicular Skeleton

• The appendicular skeleton consists of 126 bones
• It is appended to the axial skeleton
• The appendicular skeleton includes:
• Shoulder girdle: clavicle and scapula = 4
• Upper limb: humerus, radius, ulna, carpals, metacarpals, and phalanges = 60
• Pelvic girdle: coxal bone (ilium, ischium, and pubis) = 2 bones
• Lower limb: femur, tibia, fibula, tarsals, metatarsals, and phalanges = 60

Functions of Bone

• Support: provides a framework to maintain posture, supports soft tissues, and bears weight
• Protection: protects critical organs like the brain (by the skull), heart and lungs (by the ribs)
• Movement: acts as levers on which muscles pull to produce movement
• Hematopoiesis: the production of red blood cells
• Storage of minerals and fats, such as calcium and phosphate

Types of Bones

• Long bones
• Short bones
• Flat bones
• Irregular bones
• Sesamoid bones

Long Bones

• Long bones have a long cylindrical shaft that contains the medullary cavity and serves as levers
• Examples include the Femur, Tibia, Fibula, Humerus, Ulna, Radius, Phalanges, Metatarsals, and Metacarpals

Short Bones

• Short bones are small and cube-shaped with a large articular surface, providing shock absorption
• Examples include the tarsals (talus) and carpals (capitate)

Flat Bones

• Flat bones have are curved and thin, providing protection
• Examples include the skull, sternum, scapula, clavicle, rib, and ilium

Irregular Bones

• Irregular bones serve a variety of purposes
• Examples include the entire spine (vertebra), sacrum, ischium, pubis, maxilla, and mandible

Sesamoid Bones

• Sesamoid bones provide protection and mechanical advantage to musculotendinous units
• Examples include: patella, great toe, and thumb

Bone Composition

• Bone cells: 10%
• Organic material (collagen): 10%
• Inorganic material (calcium carbonate): 60%
• Water weight: 20%

Major Parts of a Bone

• Compact bone
• Spongy bone

Typical Long Bony Features

Epiphysis

• The epiphysis is spongy/trabecular/cancellous bone located at the ends of long bones

Epiphyseal Plate

• The epiphyseal plate, or growth plate, is a thin cartilage plate that separates the diaphysis and epiphyses

Diaphysis

• The diaphysis is the compact bone forming the long cylindrical shaft

Typical Bone Features

Periosteum

• Periosteum is a dense, fibrous membrane covering the outer surface of the diaphysis

Endosteum

• Endosteum is a fibrous membrane that lines the inside of the cortex

Medullary Cavity

• The medullary or marrow cavity lies between the walls of the diaphysis and contains yellow or fatty marrow

Articular Cartilage

• Articular cartilage is a hyaline cartilage covering the epiphysis which provides cushioning effect and reduce friction

Epiphyseal Closure Timetable

• Longitudinal growth continues when epiphyseal plates are open.
• Wolff's Law states that bone under stress will thicken to form a stronger, osseous matrix.
• Shortly after adolescence, epiphyseal plates disappear and close; most close by age 18, but some may remain open until age 25.

Types of Joints

• Joints are classified by structure and function, including fibrous, cartilaginous, and synovial types.

Types of Joints - Synarthrodial

• Synarthrodial joints are immovable with a fibrous structure
• Suture joints are the Skull sutures
• Gomphosis joints are teeth fitting into the mandible or maxilla

Types of Joints - Amphiarthrodial

• Amphiarthrodial joints are slightly movable with fibrous and cartilaginous structures
• Syndesmosis joints are fibrous, such as the coracoclavicular and inferior tibiofibular joints
• Symphysis joints are cartilaginous, such as the symphysis pubis and intervertebral discs
• Synchondrosis joints are cartilaginous, like the costochondral joints of the ribs with the sternum

Types of Joints - Diarthrodial

• Diarthrodial joints are freely movable synovial joints which are composed of a joint capsule
• They secrete and absorb synovial fluid to lubricate the joint cavity
• They absorbs shock and protects the bone during weight bearing, compression, unloading or distractions

Synovial Joints

• Ball-and-Socket (Enarthrodial)
• Hinge (Ginglymus)
• Gliding/Plane (Arthrodial)
• Ellipsoid (Condyloidal)
• Saddle (Sellar)
• Pivot/Screw (Trochoidal)

Bone Markings - Processes

• Processes are elevations and projections that form joints

Condyle

• Condyles are large, round processes that usually articulate with another bone, such as the medial/lateral condyle of the femur

Facet

• Facets are small, nearly flat surfaces, such as the articular facet of a vertebra

Head

• The Head is an enlargement on the end of a bone, such as the head of the humerus

Bone Markings (cont.) - Processes for attachment

• Processes serve as a point of attachment for muscles, tendons, or ligaments

Crest

• Crests are narrow, ridgelike projections, such as the iliac crest of the pelvis

Epicondyle

• Epicondyles are projections situated above a condyle, such as the medial/lateral epicondyle of the humerus

Process:

• Processes are any prominent projection on a bone, like the olecranon process of humerus.

Spine

• Spine (or spinous process) is a sharp, slender projection, such as the spine of the scapula

Tubercle

• Tubercles are small, round projections, such as the greater/lesser tubercles of the humerus or the adductor tubercle of the femur

Tuberosity:

• Tuberosity refers to a large, rounded or roughened projection, such as the tibial tuberosity.

Trochanter

• Trochanters are very large processes, such as the great/lesser trochanter of the femur.

Bone Markings (cont.) - Cavities

• Cavities are depressions in bones

Foramen

• Foramen are rounded holes or openings in bones, such as the obturator foramen in the pelvis or the foramen magnum of the skull.

Fossa

• A Fossa is a hollow, depressed, or flattened surface, such as the supraspinatus fossa or glenoid fossa of the scapula

Types of Joint Motion

• Physiological joint motion occurs in planes of motion about an axis at the joint.
• Osteokinematics involves the bone movements relative to the three cardinal planes.
• Arthrokinematics deals with the small, unseen movement within the joint, between the joint surfaces (concave–convex), including accessory motion:
• Roll (rock): tire rolling
• Glide (slide): tire skidding
• Spin: tire spinning

Movement in Joints

• Range of Motion (ROM)
• A joint normally moves freely and painlessly
• Goniometry
• Used to measure available ROM in a joint
• Manual and digital goniometers are used as tools
• Hypermobility
• Extra range of motion
• Control is seen in circus performers and gymnasts
• Instability can lead to injury
• Hypomobility
• Chronically tight
• Results in muscle strains
• Results in pinched nerves and injury

This lesson covers the basics of Osteology and the human skeleton. It describes the bones of the axial and appendicular skeleton. Key bones include the skull, vertebrae, ribs, clavicle, scapula, humerus, radius, ulna, femur, tibia, and fibula.