(VIDEO) The Human Skeleton

Introduction

• The human skeleton is a complex and vital structure that serves as the framework for the human body. COmprised of approximately 206 bones in adults, along with cartilage, joints, and ligaments, the skeletal system accounts for about 20% of a person’s body mass. Understanding the skeletal system is essential not only for comprehending human anatomy but also appreciating how bodily movements and structural integrity are maintained. This chapter will delve into the major components of human skeleton, notably the axial skeleton and appendicular skeleton, while highlighting critical vocabulary and concepts.

The Axial Skeleton

• The axial skeleton forms the central core of the body, consisting of the skull, vertebral column, and thoracic cage.

The Skull

• Structure: Composed of 22 bones, the skull protects the brain and provides structure to the face.

• Cranial and Facial Bones:

  • The cranial bones (8 total) include the frontal bone, two parietal bones, occipital bone, two temporal bones, sphenoid bone, and the ethmoid bone.

  • the facial bones (14 total) consist of the mandible, maxillary bones, zygomatic bones, nasal bones, vomer, and inferior nasal conchae.

• Sutures: Bones in the skull are connected by sutures, such as the coronal, sagittal, lambdoid, squamous, and occipitomastoid sutures.

• Foramina: Openings for nerves and blood vessels, including the foramen magnum, which allows the spinal cord to pass through.

The Vertebral Column

• Comprised of 26 irregular bones, the vertebral column supports the skull and pelvis and provides flexibility through its S-shape.

• Sections of the Spine:

  • Cervical Vertebrae: 7 vertebrae at the top.

  • Thoracic Vertebrae: 12 vertebrae in the middle.

  • Lumbar Vertebrae: 5 larger vertebrae at the bottom.

• Sacrum and Coccyx: The sacrum consists of 5 fused vertebrae, while the coccyx, or tailbone, is made of a few tiny fused vertebrae.

• Ligaments and Discs: The column is supported by ligaments like the anterior and posterior longitudinal ligaments and intervertebral discs, which act as shock absorbers.

The Thoracic Cage

• The thoracic cage includes the sternum and ribs.

• Sternum: A flat bone composed of three fused parts: the manubrium, body, and xiphoid process.

• Ribs: 12 pairs of ribs are categorized into:

  • True Ribs: First 7 pairs that attach directly to the sternum.

  • False Ribs: 5 pairs, including 3 that attach indirectly and 2 floating ribs that do not attach to the sternum.

The Appendicular Skeleton

• The appendicular skeleton primarily consists of the limbs and their supporting structures.

The Pectoral Girdle

• Comprised of the clavicle (collarbone) and scapula (shoulder blade), it connects the upper limbs to the axial skeleton.

• The clavicle has a sternal end that attaches to the manubrium and an acromial end that connects to the scapula.

The Upper Limb

• The upper limb includes the humerus in the arm, radius and ulna in the forearm, and intricate structures in the hand.

• The humerus features components such as the greater and lesser tubercle and epicondyles.

• The forearm consists of the radius and ulna, connected by the interosseous membrane.

• The hand is formed of carpals (8 short bones), metacarpals (5 long bones), and phalanges (14 bones), with the thumb having two phalanges.

The Pelvic Girdle

• The pelvic girdle consists of two hip bones that connect the lower limbs to the axial skeleton, providing more stability than mobility.

• The hip bones, which fuse from three parts (ilium, ischium, pubis) by adulthood, support the pelvic region.

The Lower LImb

• The lower limb features robust structures suitable for weight-bearing activities.

• The femur is the largest bone in the body, with several key features, including the greater and lesser trochanters.

• The tibia and fibula form the leg, with the tibia being larger and sturdier.

• The foot mirrors the hand’s structure, with tarsals (7 bones), metatarsals (5 bones), and phalanges (14 bones), where the big toe has two phalanges.

Conclusion

• In summary, the human skeleton is an intricate system crucial for protection, support, and movement. Understanding the axial and appendicular skeleton provides insight into how the body’s structure functions as a cohesive unit. The detailed examination of each component, from the skull to the limbs, emphasizes the importance of bones, joints, and ligaments in maintaining bodily integrity and facilitating movement. THis foundational knowledge is essential for further studies in anatomy and physiology, as well as applications in health and medicine. The skeletal system not only supports the physical form but also plays a pivotal role in overall health and mobility, underscoring its significance in human biology.