Tendons are strong, inelastic fibrous connective tissue cords that connect muscles to bones. They transmit the pulling force of muscle contraction to move the bone. Tendons are composed of dense regular collagen fibres. The largest tendon in the body is the Achilles Tendon (calcaneal tendon) - connects the calf muscles (gastrocnemius and soleus) to the heel bone (calcaneus). Tendon injuries are called tendinitis (inflammation) or ruptures.

The adult human body has 206 bones. At birth, a baby has approximately 270-300 bones, but many fuse together during growth and development. By adulthood (around age 25), the number stabilizes at 206. The process of bone fusion is called synostosis. The skeletal system forms the framework of the body, supports soft tissues, protects vital organs, and enables movement.

Each human hand contains 27 bones: Carpals (wrist bones) = 8 bones (arranged in 2 rows), Metacarpals (palm bones) = 5 bones, Phalanges (finger bones) = 14 bones (3 per finger x 4 fingers + 2 for thumb). Total = 8 + 5 + 14 = 27 bones per hand. Both hands together = 54 bones, making the hands the most bone-rich region of the body. The hand's complex bone structure allows for precise and varied movements.

The Femur (thigh bone) is the longest, largest, and strongest bone in the human body. It extends from the hip joint to the knee joint. The femur bears the entire weight of the body when standing. Its average length in an adult male is approximately 45-50 cm. The femur also contains the largest amount of red bone marrow, making it a major site of blood cell production.

Osteoporosis (meaning porous bones) is a condition where bone density decreases, making bones weak, brittle, and prone to fractures. It occurs when the rate of bone resorption exceeds bone formation. Risk factors: Age (most common in elderly), Post-menopausal women (due to decreased oestrogen), Calcium and Vitamin D deficiency, Physical inactivity, smoking, alcohol. Prevention: adequate calcium and Vitamin D intake, weight-bearing exercise.

The Stapes (stirrup bone) is the smallest bone in the human body, measuring approximately 3 mm in length. It is located in the middle ear and is one of the three ossicles (small bones) - Malleus (hammer), Incus (anvil), and Stapes (stirrup). These three bones transmit sound vibrations from the eardrum to the inner ear. The stapes is shaped like a stirrup, hence the name.

Tooth enamel is the hardest substance in the human body. It covers the crown of the tooth and is composed of 96% hydroxyapatite (a crystalline calcium phosphate mineral). Despite being the hardest substance, enamel is brittle and cannot regenerate once damaged, as it contains no living cells. Bone is the second hardest structure. Enamel protects the softer dentine and pulp beneath it.

The human skull consists of 22 bones in total: Cranial bones (8) - protect the brain (Frontal, Parietal x2, Temporal x2, Occipital, Sphenoid, Ethmoid) and Facial bones (14) - form the face (Maxilla x2, Mandible, Zygomatic x2, Nasal x2, Lacrimal x2, Palatine x2, Inferior nasal conchae x2, Vomer). The Mandible (lower jaw) is the only movable bone of the skull.

The Mandible (lower jaw bone) is the only movable bone in the skull. It forms the lower jaw and holds the lower teeth. The mandible articulates with the temporal bone at the Temporomandibular Joint (TMJ), which allows movements for chewing (mastication), speaking, and swallowing. All other bones of the skull are fused together by immovable joints called sutures.

The human vertebral column (spine) consists of 33 vertebrae in children, but in adults several fuse: Cervical (7), Thoracic (12), Lumbar (5), Sacral (5 fused into 1 sacrum), Coccygeal (4 fused into 1 coccyx). Total = 7+12+5+5+4 = 33. In adults, the sacral and coccygeal vertebrae fuse, leaving 26 bones in the adult vertebral column.