Study sheet: Locomotor System and Osteology

📋 Course Outline

1. Locomotor System Organization
2. Bone Definition and Cartilage
3. Bone Growth and Ossification
4. Bone Classification
5. Bone Color and Composition
6. Functions of Bones

📖 1. Locomotor System Organization

🔑 Key Concepts & Definitions

• Locomotor system : A coordinated set of bones, muscles, tendons, ligaments, cartilage, fascia, vessels, nerves, subcutaneous cellular tissue, and skin guided by signals from the nervous system.

📝 Essential Points

• The locomotor system provides support and protection, enables stability and movement during interaction with the environment, and forms a framework in which vital organs reside.

📌 The appendicular skeleton consists of two right and left thoracic limbs and two right and left pelvic limbs, whereas the axial skeleton consists of the head, laryngeal skeleton, thoracic cage, and rachis.

💡 Memory Hook

Axial skeleton forms the central framework, whereas appendicular skeleton forms the four limbs.

📖 2. Bone Definition and Cartilage

🔑 Key Concepts & Definitions

• Bone : A rigid, hard, resistant, highly vascularized, and innervated constitutive part of the skeleton impregnated with calcareous salts.
• Cartilage : A hard and flexible tissue composed of 80% water that is hypovascularized and non-innervated.

★ Must-know

• Bones support soft parts and form skeletal walls for the cavities of the human body.

• Bone tissue comes from hyaline cartilaginous tissue.

Further detail

• The three types of cartilage are:
  • hyaline cartilage
  • elastic cartilage
  • fibrous cartilage or fibrocartilage

💡 Memory Hook

Bone is rigid, vascularized, and innervated, whereas cartilage is flexible, hypovascularized, and non-innervated.

📖 3. Bone Growth and Ossification

★ Must-know

• Ossification, or osteogenesis, is the transformation of cartilaginous tissue into bone tissue that begins during embryonic life and continues until puberty or beyond.

📌 Endochondral ossification occurs in hyaline cartilage and is exemplified by long bones such as the humerus, whereas fibrous or intramembranous ossification develops from membranous fibrous tissue and is exemplified by flat bones of the skull.

Further detail

• The skeleton of a six-week-old embryo is composed only of fibrous tissue and hyaline cartilage.

💡 Memory Hook

Fibrous tissue → hyaline cartilage → bone tissue

📖 4. Bone Classification

★ Must-know

📌 A long bone has a length significantly greater than its width and thickness, as in the humerus, femur, and radius.

📌 A flat bone has length and width significantly greater than thickness, as in the scapula and sternum.

Further detail

📌 A short bone has three approximately equal dimensions, as in the tarsal and carpal bones.

📌 An irregular bone is difficult to measure because it is composed of different parts, as in the coxal bone.

💡 Memory Hook

L-F-S-I: long, flat, short, irregular

📖 5. Bone Color and Composition

★ Must-know

• The skeleton generally contains 200 constant bones plus three pairs of ear ossicles, while additional inconstant and variable bones may include sesamoid and Wormian bones.

• From the surface to the depth, a long bone contains: the periosteum, the compact cortex, the spongy medulla with bone marrow, the endosteum, the medullary canal rich in yellow bone marrow

• From the surface to the depth, a flat or short bone contains:
  • the periosteum
  • the compact external lamina
  • the spongy diploe rich in red bone marrow
  • the compact internal lamina

Further detail

• Bone color is pinkish-white in living beings and yellowish-white in cadavers.

💡 Memory Hook

Periosteum → cortex → medulla → endosteum

📖 6. Functions of Bones

★ Must-know

• Bones shape the body, support and cushion soft organs, protect vital organs, enable voluntary movement through muscle contraction, provide stability with joints ligaments and tendons, store minerals such as calcium, and support hematopoiesis through bone marrow.

Further detail

• The skull protects the brain, the rib cage protects the heart and lungs, and the spine protects the spinal cord.

• Bones store minerals such as calcium and release them into the blood when needed.

• Bone marrow provides the matrix for the formation of red blood cells.

💡 Memory Hook

Support, protection, movement, stability, minerals, blood

📊 Synthesis Tables

Axial and appendicular skeleton

Skeleton	Components	Role in organization
Appendicular skeleton	Two thoracic limbs and two pelvic limbs	Forms the four limbs
Axial skeleton	Head, laryngeal skeleton, thoracic cage, and rachis	Forms the central body framework