Chapter 1: The Skeletal System

Comprehensive vocabulary flashcards covering anatomical terminology, histological features, chemical composition, skeletal divisions, joint classifications, and common pathologies from Chapter 1: Skeletal System.

Skeleton

The hard supportive framework of the body that provides rigid support, maintains posture and body straightness, connects with movement organs, and protects significant organs like the brain, lungs, and heart.

Movement System

The integrated physiological system composed of muscles and bones, where muscles generate the power required for movement and bones support them to convert that power into actual motion.

Osteocytes

Star-like bone cells arranged in concentric circles around a central Haversian canal that secrete ossein, the solid substance of bone.

Haversian Canal

A central canal in bone tissue discovered by scientist Clapton Havers through which blood vessels pass, surrounded by circles of osteocytes.

Ossein

The solid intercellular substance of bone tissue that is secreted by osteocytes.

Periosteum

The external fibrous membrane covering the shaft (body) of a bone that contains nerves and blood vessels to nourish bone tissue.

Compact Bone

The dense, hardest layer of bone located directly beneath the periosteum that encloses the bone marrow cavity.

Spongy Bone

The porous bone tissue found at the two expanded ends of a long bone, covered by a semi-solid layer of cartilage instead of periosteum.

Collagen

A colloidal protein that constitutes a major part of the organic matter ($35\%$) of bone tissue.

Mucole

A mucous-like organic substance resembling albumin (egg white) that provides flexibility to bones and flows from bone tissue in the event of a fracture.

Inorganic Bone Materials

Mineral compounds constituting $65\%$ of bone matter—including phosphate, carbonate, calcium fluoride, manganese phosphate, and sodium chloride—responsible for bone hardness.

Axial Skeleton

The core division of the human skeleton consisting of the skull, vertebral column, and thoracic cage (sternum and ribs).

Appendicular Skeleton

The skeletal division composed of bilateral paired bones, including the pectoral girdle with upper limbs and the pelvic girdle with lower limbs.

Cranial Bones

A group of 8 interlocked bones joined by immovable joints to form a protective cranial cavity enclosing the brain.

Foramen Magnum

A relatively large aperture located at the base of the cranium through which the spinal cord passes.

Fontanelle

Membranous, fibrous cartilaginous spaces located between cranial bones in a young child's skull.

Facial Bones

A collection of 14 bones framing the eyes, nasal cavity, mouth, and ears; all are immovable except the mandible (lower jaw).

Mandible

The lower jaw bone, uniquely movable both vertically and laterally to assist in cutting, crushing, and chewing food.

Middle Ear Ossicles

Three tiny auditory bones situated within the middle ear cavity: the malleus, incus, and stapes.

Crown (Tooth)

The visible exposed region of the tooth above the gum line covered by enamel.

Root (Tooth)

The lower region of the tooth anchored into the socket of the jawbone and covered by cementum.

Neck (Tooth)

The narrow transitional region of the tooth positioned between the crown and root, enveloped by the gum.

Dentine

A dense, calcified hard tissue that constitutes the bulk and primary substance of a tooth.

Enamel

The hard, glistening, white outer protective layer covering the anatomical crown of a tooth.

Cementum

A rough, brown, solid bone-like substance that coats the anatomical neck and root of a tooth.

Pulp

The vascular and neural inner central cavity of a tooth containing branched blood vessels and dental nerves that register sensation (pain, heat, cold, and pressure).

Apical Foramen

A tiny aperture located at the apex of the tooth root through which dental nerves and blood vessels gain entry to the pulp cavity.

Deciduous Teeth

Also called milk or temporary teeth; a set of 20 teeth (10 in each jaw) emerging after 6 months of age, completing by the first year, and shedding between 6 and 7 years of age.

Permanent Teeth

The adult dentition totaling 32 teeth (16 per jaw) that begins emerging around age 7 and reaches completion after puberty, with wisdom teeth appearing as late as age 32.

Teeth Implant

A surgical procedure to embed an artificial replacement tooth into the jawbone for decayed teeth, rarely performed due to high cost and extended treatment time.

Gum Inflammation

A microbial infection characterized by split gums and halitosis (bad breath), with increased incidence from smoking, alcohol, and poor nutrition.

Vertebral Column

The longitudinal flexible bony axis of the human trunk measuring $75\text{ cm}$ in an adult, composed of 33 individual vertebrae separated by intervertebral discs.

Cartilaginous Discs

Fibrocartilaginous pads positioned between adjacent vertebrae that facilitate multi-directional bending, promote smooth movement, and prevent friction between vertebral bodies.

Centrum

The flat, disc-like anterior weight-bearing body of a typical vertebra.

Vertebral Arch

The posterior bony arch of a vertebra that extends backward from the centrum to enclose the vertebral foramen.

Vertebral Foramen

The central aperture bounded by the centrum and the vertebral arch; the vertical alignment of these apertures creates the vertebral canal for the spinal cord.

Spinous Process

A single medial posterior bony projection of a vertebra that provides attachment points for back muscles.

Transverse Processes

A pair of lateral bony projections extending symmetrically from the sides of a vertebra that serve as attachment points for ribs.

Atlas

The first cervical vertebra ($C_1$) that articulates superiorly with the base of the skull to support the head.

Axis

The second cervical vertebra ($C_2$) possessing a long superior projection that articulates with the atlas, allowing the head to pivot, rotate, and incline.

Sacrum

A single triangular bone formed by the fusion of five cohesive sacral vertebrae.

Coccyx

The terminal bone of the spinal column formed by the fusion of four cohesive coccygeal vertebrae.

True Ribs

The first 7 pairs of ribs that articulate directly with the sternum anteriorly via individual small cartilaginous pieces.

False Ribs

The 8th, 9th, and 10th pairs of ribs that attach indirectly to the sternum by fusing with the costal cartilage of the 7th rib.

Free Ribs

The 11th and 12th pairs of ribs whose anterior ends remain unattached to the sternum or adjacent costal cartilage.

Cartilaginous Pieces (Costal Cartilage)

Flexible cartilage segments at the anterior ends of true and false ribs that facilitate chest expansion and movement during respiration.

Sternum

A long, flat bone composed of three fused segments situated anteriorly in the chest, featuring a pointed inferior tip and lateral attachment points for true ribs.

Scapula

A flat, triangular bone located on the posterior chest wall outside the ribs that articulates with the clavicle and provides attachment for shoulder muscles.

Clavicle

A slender, arch-like bone positioned horizontally at the base of the neck that bridges the acromion of the scapula and the manubrium of the sternum.

Humerus

The long bone of the upper arm featuring a rounded proximal head that forms a ball-and-socket joint with the shoulder girdle and distal articulation with forearm bones.

Ulna

The longer and medial of the two forearm bones, aligned longitudinally with the little finger.

Radius

The lateral bone of the forearm aligned with the thumb that rotates around the ulna during forearm movements.

Carpal Bones

A group of 8 wrist bones organized into two transverse rows of 4 bones each.

Metacarpal Bones

The 5 elongated bones that form the bony architecture of the palm of the hand.

Phalanges (Hand)

The 14 miniature long bones that form the fingers, with three in each finger and two in the thumb.

Pelvic Girdle

A basin-like skeletal ring composed of two symmetrical hip bones, each formed by the fusion of three bones: ilium, ischium, and pubis.

Femur

The longest and strongest bone in the human body, possessing a spherical proximal head that articulates with the acetabulum of the pelvis.

Tibia

The larger, medial, weight-bearing bone of the lower leg that articulates superiorly with the femur at the knee joint.

Fibula

The slender, lateral bone of the leg firmly attached to the tibia at both ends, which does not rotate around the tibia.

Patella

A small, flattened sesamoid bone situated anterior to the knee joint to protect the joint from injury.

Tarsals

A cluster of 7 bones forming the ankle and heel of the foot, corresponding to the carpals of the wrist.

Hallux

The big toe of the foot, which contains only two phalanges and exhibits limited mobility compared to the thumb to facilitate walking.

Bone Fracture

The mechanical splitting or division of a bone into two or more pieces caused by violent muscular contractions, physical trauma, or underlying disease (such as tuberculosis or cancer).

Dis-articulation

The pathological or traumatic separation of two articulating bones at a joint where the bones remain intact but connecting fibrous ligaments are torn.

Ligaments

Tough, flexible fibrous bands that bind bones together at joints, guide physiological motion, and safeguard against joint dislocation.

Tendons

Firm, non-flexible cords of dense fibrous connective tissue that anchor skeletal muscles to bones.

Cartilage

A smooth, semi-translucent, white resilient connective tissue that covers articular ends of bones to absorb impact and eliminate friction.

Ball and Socket Joint

A multi-axial synovial joint (such as the shoulder or hip) in which a spherical bone head fits into a cup-shaped cavity, enabling rotational movement in all planes.

Hinge Joint

A uniaxial synovial joint (such as the elbow or knee) that restricts motion strictly to one plane, similar to the action of a door hinge.

Cylindrical Joint

A pivot joint permitting rotational movement around a single central axis, exemplified by the articulation of the atlas vertebra with the occipital bone.

Immovable Joints

Synarthrotic, fixed bone junctions interlocked by fibrous sutures with no movement permitted, such as the cranial sutures uniting cranial bones.

Rickets

A metabolic bone disease affecting young children (ages 1–2) caused by vitamin D deficiency and lack of sunlight exposure, characterized by soft bones, bowed legs, and delayed teething and walking.