FSHP Academy
Human Anatomy — all lessons

Foundations of Anatomy

Anatomical terminology, planes, axes and movement directions

The Skeletal System

Skeletal system: structure and functionsBone structure, remodelling and adaptation to loading

Joints and the Muscular System

Joint types and classificationJoint mechanics: arthrokinematics and stabilityThe muscular system: organisation and major muscle groupsMuscle architecture: pennation, length and cross-sectional areaMuscle fibre types

Regional Functional Anatomy

Spine and postureThe shoulder complexThe hip complexThe knee complexThe ankle and foot complexCore and pelvic stabilityElbow and wrist functional anatomyCervical and thoracic spine functional anatomy

Skeletal system: structure and functions

How the 206 bones of the adult skeleton are organised, what they do beyond holding us up, and why the skeleton is a living, adaptable tissue.

Beginner Evidence: Established consensus 3 min read Reviewed 2026-10-31 Status: draft

Learning objectives

  • Name the divisions of the skeleton and the main bones of each
  • Describe the six functions of the skeletal system
  • Classify bones by shape and relate shape to function
  • Explain why the skeleton responds to training and disuse

Before this lesson

Why this matters

Every exercise loads the skeleton. Understanding its layout lets you name the structures involved in a movement, and understanding that bone is living tissue explains why loading strengthens it and inactivity weakens it — a theme that returns in osteoporosis and ageing.

Fundamental concepts

The adult skeleton typically contains 206 bones (numbers vary slightly between individuals because of extra sesamoid or sutural bones) [openstax2022axial].

DivisionComponentsMain role
Axial skeleton (80 bones)Skull, hyoid, auditory ossicles, vertebral column, ribs, sternumCentral support, protection of brain, spinal cord and thoracic organs
Appendicular skeleton (126 bones)Pectoral girdle (scapula, clavicle), upper limbs, pelvic girdle (hip bones), lower limbsLocomotion and manipulation

Functions of the skeleton

  1. Support — a rigid framework that maintains shape and carries body weight.
  2. Protection — the skull, ribcage and vertebrae shield vital organs.
  3. Movement — bones act as levers; muscles pull on them across joints (see levers).
  4. Mineral storage — about 99% of body calcium and most phosphate are stored in bone and released as needed [openstax2022bone].
  5. Blood-cell production (haematopoiesis) — in red marrow, found in adults mainly in the pelvis, vertebrae, ribs, sternum, skull and proximal femur and humerus.
  6. Energy storage and endocrine roles — yellow marrow stores fat; bone cells release hormones (such as osteocalcin and FGF23) that act on other tissues, an active research area.

Bone shapes

ShapeDescriptionExamplesFunctional advantage
LongLonger than wide, shaft + two endsFemur, humerus, phalangesLevers for movement
ShortCube-likeCarpals, tarsalsStability with small movements
FlatThin, often curvedSternum, ribs, scapula, skull bonesProtection, broad muscle attachment
IrregularComplex shapesVertebrae, pelvisSpecialised (e.g., spinal protection + load bearing)
SesamoidWithin tendonsPatellaIncrease tendon moment arm, reduce friction

Bone internal structure is covered in bone structure.

The skeleton is adaptable

Bone is constantly broken down and rebuilt (remodelled). Frost’s mechanostat model describes bone adjusting its mass and architecture to the strains it regularly experiences: sufficient loading maintains or adds bone; prolonged unloading (bed rest, spaceflight, immobilisation) leads to loss [frost2003].

Common mistakes and misconceptions

  • “The shoulder girdle is part of the axial skeleton.” The scapula and clavicle are appendicular; the only bony link from arm to trunk is the sternoclavicular joint.
  • “All marrow makes blood cells.” In adults much of the long-bone shaft contains yellow (fatty) marrow.

Assessment and practical tools

Bone mineral density is measured clinically by dual-energy X-ray absorptiometry (DXA); trainers do not measure or diagnose bone health but should know a client’s DXA results and clinician guidance when programming.

Case study

Client: Lakshmi, 58, post-menopausal, swims five times a week and asks if this protects her bones. The trainer explains that swimming is excellent for cardiovascular fitness but provides little skeletal loading, and — with her doctor’s agreement — adds progressive resistance training and low-level impact work, linking to bone structure and osteoporosis.

Further learning: video lessons

Video links are only marked “verified” after a human has watched them. Unverified entries open a YouTube search for that channel and topic rather than a guessed link.

Introductory needs verification — opens a YouTube search

The skeletal system — overview

Crash Course

You will understand: the divisions and functions of the skeleton

Why: Clear beginner introduction.
Technical needs verification — opens a YouTube search

Axial and appendicular skeleton — bone by bone

Kenhub

You will understand: identifying the major bones and landmarks

Why: Anatomy-focused educator with labelled visuals.

Knowledge check

Knowledge check · 0/5

1. Which belongs to the axial skeleton?

Answer C. The axial skeleton is the skull, vertebral column, ribs and sternum. The scapula and clavicle form the shoulder (pectoral) girdle, part of the appendicular skeleton.

2. Red blood cells in adults are mainly produced in…

Answer B. In adults, haematopoiesis occurs mainly in red marrow in the pelvis, vertebrae, ribs, sternum, skull and proximal ends of the femur and humerus.

3. The patella is an example of a…

Answer C. Sesamoid bones develop within tendons. The patella increases the quadriceps' moment arm at the knee.

4. In bones, muscles generate movement mainly by…

Answer B. Muscles pull via tendons on bones, which rotate around joints acting as levers.

5. Approximately what proportion of the body's calcium is stored in bone?

Answer C. About 99% of body calcium is held in bone and teeth, making bone the main mineral reservoir.

Short-answer & application questions

  1. Give one example each of a long, short, flat, irregular and sesamoid bone and explain how its shape suits its function.
  2. Explain why an astronaut or a bed-bound patient loses bone mass.
  3. Which bones would you expect to be most affected by a weight-bearing jumping programme, and why?

Key takeaways

  • The adult skeleton usually has 206 bones, divided into the axial (skull, spine, ribs, sternum) and appendicular (limbs and girdles) skeletons.
  • Functions include support, protection, movement (as levers), mineral storage, blood-cell production and endocrine signalling.
  • Bone shape (long, short, flat, irregular, sesamoid) reflects its job.
  • Bone is living tissue that is constantly remodelled and responds to mechanical loading.

Connected topics

anatomy

Bone structure, remodelling and adaptation to loading

anatomy

Joint types and classification

anatomy

Spine and posture

womens health

Osteoporosis

geriatric fitness

Physiology of ageing: sarcopenia, dynapenia, osteopenia

References

  1. Betts JG, Young KA, Wise JA, et al. (2022). Anatomy and Physiology 2e — Chapter 6: Bone Tissue and the Skeletal System. OpenStax, Rice University. · Link Textbook check pending
  2. Betts JG, Young KA, Wise JA, et al. (2022). Anatomy and Physiology 2e — Chapters 7–8: Axial and Appendicular Skeleton. OpenStax, Rice University. · Link Textbook check pending
  3. Frost HM (2003). Bone's mechanostat: a 2003 update. The Anatomical Record Part A, 275(2):1081–1101. doi:10.1002/ar.a.10119 Narrative review check pending

Educational content only — not medical advice. Consult a qualified clinician for diagnosis or treatment.