Human skeleton anatomy
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human skeleton anatomy overview bones labeled diagram
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I now have excellent material from Gray's Anatomy for Students plus two detailed labeled diagrams. Here is a thorough overview:
Human Skeleton Anatomy
Labeled Diagrams
Overview
The adult human skeleton contains 206 bones. These are organized into two major divisions:
| Division | Bones | Count |
|---|---|---|
| Axial skeleton | Skull, vertebral column, ribs, sternum | 80 |
| Appendicular skeleton | Upper limbs, lower limbs, shoulder girdles, pelvic girdle | 126 |
- Gray's Anatomy for Students - "The skeleton can be divided into two subgroups, the axial skeleton and the appendicular skeleton."
1. Axial Skeleton (80 bones)
Skull
- Neurocranium (braincase): frontal, 2 parietal, 2 temporal, occipital, sphenoid, ethmoid
- Viscerocranium (face): nasal, maxilla, lacrimal, zygomatic, palatine, inferior nasal conchae, vomer, mandible
- Hyoid bone (throat, supports tongue)
- Ear ossicles (3 per side): malleus, incus, stapes
Vertebral Column (33 vertebrae total)
| Region | Number | Key Features |
|---|---|---|
| Cervical | 7 (C1-C7) | C1 = Atlas, C2 = Axis; support head, allow rotation |
| Thoracic | 12 (T1-T12) | Articulate with ribs |
| Lumbar | 5 (L1-L5) | Largest vertebrae; bear body weight |
| Sacrum | 5 fused | Forms posterior wall of pelvis |
| Coccyx | 4 fused | Vestigial tailbone |
Thorax
- Sternum: manubrium + body + xiphoid process
- 12 pairs of ribs: True ribs (1-7, attach directly to sternum), False ribs (8-10, attach via costal cartilage), Floating ribs (11-12, no anterior attachment)
2. Appendicular Skeleton (126 bones)
Shoulder Girdle (4 bones)
- Clavicle (collarbone) x2
- Scapula (shoulder blade) x2
Upper Limb (each side = 30 bones)
| Segment | Bones |
|---|---|
| Arm | Humerus |
| Forearm | Radius + Ulna |
| Wrist (carpals) | Scaphoid, lunate, triquetrum, pisiform, trapezium, trapezoid, capitate, hamate (8 per wrist) |
| Palm (metacarpals) | 5 metacarpals |
| Fingers (phalanges) | 14 phalanges (2 in thumb, 3 in each finger) |
Pelvic Girdle (2 hip bones)
- Each hip bone = ilium + ischium + pubis (fused in adults)
- Together with sacrum they form the bony pelvis
- Key landmarks: anterior superior iliac spine (ASIS), pubic symphysis, obturator foramen, acetabulum
Lower Limb (each side = 30 bones)
| Segment | Bones |
|---|---|
| Thigh | Femur (longest bone in body) |
| Kneecap | Patella (largest sesamoid bone) |
| Leg | Tibia + Fibula |
| Ankle (tarsals) | Talus, calcaneus, navicular, cuboid, 3 cuneiforms (7 per ankle) |
| Foot (metatarsals) | 5 metatarsals |
| Toes (phalanges) | 14 phalanges |
Bone Structure & Types
Bone Types by Shape
| Type | Description | Example |
|---|---|---|
| Long bones | Tubular; shaft + two epiphyses | Humerus, femur, tibia |
| Short bones | Cuboidal | Carpals, tarsals |
| Flat bones | Two compact plates + spongy bone between | Skull, sternum, scapula |
| Irregular bones | Varied complex shapes | Vertebrae, facial bones |
| Sesamoid bones | Develop within tendons | Patella, sesamoids of thumb |
Bone Tissue
- Compact bone: Dense outer shell of all bones
- Spongy (trabecular/cancellous) bone: Internal lattice containing marrow cavities; site of blood cell production
Blood Supply & Innervation
- A nutrient artery (one per bone) enters the internal cavity and supplies marrow, spongy bone, and inner compact bone layers
- The periosteum (fibrous outer membrane) covers all bone surfaces except at joint cartilage; it is richly supplied with sensory nerves and is very pain-sensitive
- Bone itself has few sensory nerve fibers; most internal nerve fibers are vasomotor
Cartilage
Three types of cartilage are found in the skeleton:
| Type | Features | Location |
|---|---|---|
| Hyaline | Most common; moderate collagen | Articular surfaces, costal cartilages, growth plates |
| Elastic | Collagen + elastic fibers | External ear, epiglottis |
| Fibrocartilage | Dense collagen, few cells | Intervertebral discs, pubic symphysis, knee menisci |
Cartilage is avascular - nourished entirely by diffusion. It has no blood vessels, lymphatics, or nerves.
Functions of the Skeleton
The skeleton serves five main functions:
- Support - structural framework for the body
- Protection - shields vital organs (skull protects brain; rib cage protects heart and lungs)
- Mineral reservoir - stores calcium and phosphorus
- Movement - levers for muscular action
- Haematopoiesis - spongy bone cavities house bone marrow for blood cell production
Bone Development
- Intramembranous ossification: Mesenchyme ossifies directly without a cartilage model (flat bones of the cranium)
- Endochondral ossification: Cartilaginous model forms first, then ossifies; used for most bones including long bones and the appendicular skeleton
- Ossification centers appear by the end of the embryonic period (about 56 days)
- Skeletal maturity is typically reached between ages 20-25
Skeletal Age Assessment
Skeletal maturity can be assessed by radiographing the non-dominant (left) hand and comparing to standard reference radiographs. This is clinically useful in evaluating growth disorders, malnutrition, and hypothyroidism.
For a great visual walkthrough, this video covers the bones of the skeleton clearly:
Sources: Gray's Anatomy for Students; The Developing Human: Clinically Oriented Embryology; Wikipedia - List of bones
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