Human Bone Structure and Skeleton Types

Bone Structure

• Bones are composed of:
  • Compact bone: dense, outer layer
  • Cancellous bone: spongy, inner layer
  • Bone marrow: spongy tissue inside bones
• Bone tissue is made up of:
  • Osteoblasts: bone-forming cells
  • Osteoclasts: bone-resorbing cells
  • Osteocytes: mature bone cells

Skeleton Types

• Two main types:
  • Endoskeleton: internal skeleton, found in vertebrates
  • Exoskeleton: external skeleton, found in invertebrates (e.g., insects, crustaceans)
• Vertebrate skeletons can be further classified as:
  • Axial skeleton: skull, vertebrae, ribcage, sternum
  • Appendicular skeleton: limbs, pelvis, shoulder girdle

Bone Function

• Support and protection:
  • Provide framework for body
  • Protect internal organs
• Movement and locomotion:
  • Act as levers for muscles to pull on
  • Enable movement and flexibility
• Blood cell production:
  • Bone marrow produces blood cells
• Storage and regulation:
  • Store minerals (e.g., calcium, phosphorus)
  • Regulate pH and electrolyte balance

Human Skeleton

• 206 bones in the adult human skeleton
• Divided into:
  • Axial skeleton (80 bones)
  • Appendicular skeleton (126 bones)
• Major bones include:
  • Cranium (skull)
  • Sternum (breastbone)
  • Ribcage (24 ribs)
  • Vertebrae (33)
  • Pelvis
  • Long bones (e.g., femur, humerus)
  • Short bones (e.g., carpals, tarsals)

Medicines and Infectious Diseases

• Bone-related diseases:
  • Osteoporosis: bone loss and fragility
  • Osteomyelitis: bone infection
  • Bone cancer (e.g., osteosarcoma)
• Medications that affect bones:
  • Bisphosphonates: treat osteoporosis and bone cancer
  • Hormone replacement therapy: affects bone density

Muscles and Movement

• Muscles work with bones to facilitate movement
• Types of muscle movements:
  • Flexion: bending
  • Extension: straightening
  • Rotation: turning
  • Abduction: moving away from midline
  • Adduction: moving towards midline
• Muscle-bone interactions:
  • Muscles pull on bones to produce movement
  • Bones provide leverage for muscles to work efficiently

Bone Structure

• Bones are composed of compact bone, cancellous bone, and bone marrow
• Compact bone is a dense outer layer
• Cancellous bone is a spongy inner layer
• Bone marrow is a spongy tissue inside bones
• Bone tissue is made up of osteoblasts, osteoclasts, and osteocytes
• Osteoblasts are bone-forming cells
• Osteoclasts are bone-resorbing cells
• Osteocytes are mature bone cells

Skeleton Types

• There are two main skeleton types: endoskeleton and exoskeleton
• Endoskeleton is an internal skeleton found in vertebrates
• Exoskeleton is an external skeleton found in invertebrates such as insects and crustaceans
• Vertebrate skeletons can be further classified as axial and appendicular
• Axial skeleton includes skull, vertebrae, ribcage, and sternum
• Appendicular skeleton includes limbs, pelvis, and shoulder girdle

Bone Function

• Bones provide support and protection for the body
• Bones protect internal organs
• Bones act as levers for muscles to pull on, enabling movement and flexibility
• Bone marrow produces blood cells
• Bones store minerals such as calcium and phosphorus
• Bones regulate pH and electrolyte balance

Human Skeleton

• The adult human skeleton consists of 206 bones
• The skeleton is divided into axial and appendicular parts
• Axial skeleton has 80 bones including the cranium, vertebrae, and ribcage
• Appendicular skeleton has 126 bones including the upper and lower limbs, pelvis, and shoulder girdle
• Major bones include the cranium, sternum, ribcage, vertebrae, pelvis, and long and short bones

Medicines and Infectious Diseases

• Bone-related diseases include osteoporosis, osteomyelitis, and bone cancer
• Osteoporosis is a condition of bone loss and fragility
• Osteomyelitis is a bone infection
• Bone cancer includes osteosarcoma
• Bisphosphonates are used to treat osteoporosis and bone cancer
• Hormone replacement therapy affects bone density

Muscles and Movement

• Muscles work with bones to facilitate movement
• Types of muscle movements include flexion, extension, rotation, abduction, and adduction
• Flexion is the movement of bending
• Extension is the movement of straightening
• Rotation is the movement of turning
• Abduction is the movement of moving away from the midline
• Adduction is the movement of moving towards the midline
• Muscles pull on bones to produce movement
• Bones provide leverage for muscles to work efficiently

Learn about the composition of bones, including compact and cancellous bone, bone marrow, and bone tissue cells. Discover the two main types of skeletons: endoskeleton and exoskeleton.