Chapters 6&7 Bone Tissues & The Skeletal System

Axial Skeleton

Part of the skeleton that includes the skull, vertebral column, and thoracic cage (80 bones total).

Appendicular Skeleton

Includes the limbs and girdles—pectoral girdle, upper limbs, pelvic girdle, and lower limbs (126 bones).

Number of Bones in Adult Skeleton

About 206 bones.

Sutural Bones

Extra bones between skull sutures.

Sesamoid Bones

Small bones in tendons that reduce friction (e.g., patella).

Cranium

Part of skull that encloses and protects the brain (8 bones).

Facial Skeleton

Forms the shape of the face (14 bones).

Frontal Bone

Forms the forehead and roof of the orbits; contains frontal sinus and supraorbital foramen.

Parietal Bones (2)

Form the sides and roof of the cranium; connected by sagittal and coronal sutures.

Occipital Bone

Forms the back and base of skull; has foramen magnum and occipital condyles.

Temporal Bones (2)

Form sides and base of cranium; contain external acoustic meatus, mastoid, and styloid processes.

Sphenoid Bone

Forms base of cranium; has sella turcica and sphenoid sinuses.

Ethmoid Bone

Forms part of nasal cavity and orbits; includes crista galli and cribriform plates.

Maxillae (2)

Form upper jaw, hard palate, and sinuses; contain alveolar processes.

Palatine Bones (2)

Form posterior part of hard palate.

Zygomatic Bones (2)

Cheekbones; form part of the orbit; connect to temporal bones forming zygomatic arch.

Lacrimal Bones (2)

Small bones forming medial walls of orbits; contain tear duct groove.

Nasal Bones (2)

Form bridge of nose.

Vomer Bone (1)

Forms lower part of nasal septum.

Inferior Nasal Conchae (2)

Scroll-shaped bones in nasal cavity.

Mandible (1)

Lower jawbone; has ramus, mandibular condyle, coronoid process, and mental foramen.

Fontanels

Soft spots on infant skull; anterior, posterior, anterolateral, and posterolateral.

Hyoid Bone

U-shaped bone in neck; supports tongue.

Sutures

Interlocking joints between skull bones (sagittal, coronal, squamous, lambdoid).

Sinuses

Air-filled spaces in skull (maxillary, frontal, ethmoidal, sphenoidal).

Vertebral Column

Supports head and trunk, protects spinal cord; 33 bones in infant, 26 in adult.

Cervical Vertebrae (7)

Smallest vertebrae; C1 (atlas) supports head, C2 (axis) allows rotation with dens.

Thoracic Vertebrae (12)

Articulate with ribs; have long downward spinous processes.

Lumbar Vertebrae (5)

Large, thick vertebrae for weight-bearing.

Sacrum

Triangle-shaped bone of 5 fused vertebrae; contains sacral canal and foramina.

Coccyx

Tailbone; 4 fused vertebrae.

Curvatures of the Spine

Cervical & lumbar (secondary), thoracic & sacral (primary).

Typical Vertebra Parts

Body, pedicles, laminae, spinous and transverse processes, vertebral foramen.

Thoracic Cage

Includes ribs, sternum, thoracic vertebrae, costal cartilage; protects organs.

True Ribs

First 7 pairs; attach directly to sternum.

False Ribs

Pairs 8–10; attach indirectly to sternum.

Floating Ribs

Last 2 pairs; no anterior attachment.

Sternum

Breastbone; has manubrium, body, and xiphoid process.

Rib Structure

Shaft (main part), head (articulates with vertebra), tubercle (articulates with transverse process).

Pectoral Girdle

Consists of 2 clavicles and 2 scapulae; supports upper limbs.

Clavicle

S-shaped collarbone; braces scapulae.

Scapula

Shoulder blade; includes spine, acromion, coracoid process, and glenoid cavity.

Humerus

Upper arm bone; includes head, tubercles, epicondyles, trochlea, and olecranon fossa.

Radius

Lateral forearm bone; has head, radial tuberosity, and styloid process.

Ulna

Medial forearm bone; has olecranon, coronoid process, and styloid process.

Carpals (8)

Scaphoid, Lunate, Triquetrum, Pisiform, Trapezium, Trapezoid, Capitate, Hamate.

Metacarpals (5)

Bones of the palm (I–V).

Phalanges (14)

Finger bones—proximal, middle, distal (thumb = pollex).

Pelvic Girdle

Two coxal (hip) bones; attaches lower limbs, supports trunk, protects organs.

Ilium

Largest hip bone part; has iliac crest, spines, and greater sciatic notch.

Ischium

Supports weight when sitting; has spines and tuberosity.

Pubis

Front part of pelvis; has pubic symphysis and arch.

Acetabulum

Socket for femur head.

False Pelvis

Above pelvic brim; supports abdominal organs.

True Pelvis

Below pelvic brim; forms birth canal.

Female Pelvis

Wider, lighter, shallower, larger pelvic inlet.

Male Pelvis

Narrower, heavier, deeper.

Femur

Longest bone; has head, neck, greater and lesser trochanters, condyles, and epicondyles.

Patella

Kneecap; sesamoid bone in quadriceps tendon.

Tibia

Medial, weight-bearing leg bone; has condyles, tibial tuberosity, and medial malleolus.

Fibula

Thin, lateral leg bone; non-weight-bearing; has lateral malleolus.

Tarsals (7)

Ankle bones—calcaneus, talus, navicular, cuboid, and 3 cuneiforms.

Metatarsals (5)

Foot bones (I–V).

Phalanges (14)

Toe bones—proximal, middle, distal (big toe = hallux).

Calcaneus

Heel bone; largest tarsal.

Talus

Articulates with tibia; allows up-and-down foot movement.

Foramen Magnum

Large hole in occipital bone where spinal cord passes.

Mastoid Process

Bony bump behind the ear; attachment for neck muscles.

Zygomatic Arch

Cheek arch formed by zygomatic and temporal bones.

Sella Turcica

Depression in sphenoid bone that holds the pituitary gland.

Crista Galli

Projection of ethmoid bone where meninges attach.

Manubrium

Upper part of sternum that articulates with clavicles.

Functions of skeletal system

Support, protection, movement, storage of minerals, blood cell production.

Bone classification: 5 types

Long, short, flat, irregular, sesamoid.

Epiphysis

Expanded end of a long bone; filled with spongy bone and red marrow.

Diaphysis

Shaft of a long bone; mostly compact bone.

Spongy bone

Porous bone tissue in epiphyses; lightweight, supports red marrow.

Compact bone

Dense outer layer; resists compression and twisting.

Articular cartilage

Hyaline cartilage covering epiphysis; reduces friction at joints.

Periosteum

Outer connective tissue covering bone; contains blood vessels and nerves.

Perforating fibers (Sharpey’s fibers)

Collagen fibers that anchor periosteum to bone.

Medullary cavity

Hollow chamber in diaphysis; contains marrow.

Endosteum

Membrane lining medullary cavity and internal bone surfaces.

Bone marrow

Soft tissue inside bones; red = blood cell production, yellow = fat storage.

Osteons

Structural units of compact bone; look like tree rings.

Lamellae

Thin layers (rings) of bone matrix in osteons.

Central canal (Haversian canal)

Channel in center of osteon with blood vessels and nerves.

Interstitial lamellae

Leftover lamellae filling spaces between osteons.

Circumferential lamellae

Outer and inner layers of lamellae surrounding compact bone.

Perforating canals (Volkmann’s canals)

Canals connecting central canals of osteons; run perpendicular.

Trabeculae

Struts of spongy bone; house marrow; lined with endosteum.

Extracellular matrix (ECM) of bone tissue

65% inorganic (minerals) + 35% organic (collagen/proteins).

Osteoblasts

Bone-building cells; secrete organic matrix and aid mineralization.

Osteocytes

Mature bone cells in lacunae; maintain bone matrix.

Osteoclasts

Large cells that break down bone matrix; bone resorption.

Bone deposition

Process of osteoblasts building new bone tissue.

Canaliculi

Tiny canals connecting osteocytes for nutrient and waste exchange.

Osteoporosis

Bone disease where bone breakdown exceeds formation; weak and brittle bones.

Intramembranous ossification

Bone develops directly from mesenchymal tissue (skull, clavicle).