00:00The human skeleton is broadly divided into two main groups, the appendicular skeleton and the
00:05axial skeleton. The appendicular skeleton comprises the bones of the upper and lower
00:11limbs, along with the shoulder and pelvic girdles. These bones append to the central axis of the
00:18body. In contrast, the axial skeleton includes all the bones positioned along the body's central
00:24long axis. This vital framework provides support and protection for internal organs. It consists
00:31of the skull, the laryngeal skeleton, the vertebral column, and the thoracic cage. The skull is a complex
00:38structure composed of two main parts, the cranial bones and the facial skeleton. The cranial bones
00:44form the top and back of the skull, creating a protective enclosure for the brain. These eight
00:50bones include the occipital, parietal, temporal, frontal, sphenoid, and ethmoid bones. The facial
00:57skeleton, as its name suggests, forms the face of the skull. It consists of 14 bones that define the
01:05entrances to the respiratory and digestive tracts. Key facial bones include the mandible, maxillae,
01:12zygomatics, lacrimals, nasals, vomer, palatines, and nasal conchae. In fetuses and newborn infants,
01:19cranial bones are connected by flexible fibrous sutures and large regions of fibrous membranes
01:24called fontanelles. These fontanelles allow the skull to enlarge, accommodating the rapidly growing
01:30brain. Over time, fontanelles close, and sutures develop into immobile joints where cranial bones
01:36are connected by dense fibrous tissue. The four major cranial sutures are the lamdoid, coronal, sagittal,
01:44and squamous sutures. Beyond the skull, several other bones are commonly categorized with it due
01:50to their proximity and function. These include the hyoid bone, the laryngeal skeleton, and the tiny bones
01:57of the inner ear. The hyoid bone is a unique U-shaped bone located in the neck, providing an anchor point
02:04for the tongue and muscles involved in swallowing. The laryngeal skeleton, also known as the larynx or
02:09voice box, is composed of nine cartilages. It is crucial for speech as its movements regulate
02:16the tension of vocal folds to produce sounds. Inside the petrius part of the temporal bone are
02:23the three smallest bands of the body, the malleus, incus, and stapes. These inner ear bones articulate
02:30with each other, transferring vibrations from the tympanic membrane to the inner ear, which
02:35is essential for hearing. The vertebral column, commonly known as the spine, is a flexible column
02:42formed by a series of 24 individual vertebrae, plus the sacrum and coccyx. It extends from the base of
02:49the skull down to the pelvis, providing the body's central support and protecting the spinal cord.
02:55The spinal cord passes through the vertebral canal within the column. The vertebral column is divided
03:02into five distinct regions. These include the cervical spine, thoracic spine, lumbar spine,
03:08the sacral spine, and the coccygeal spine. Each region has unique characteristics and functions,
03:15contributing to the spine's overall flexibility and strength. The thoracic cage is formed by the ribs
03:22and the sternum, creating a protective enclosure for vital internal organs such as the heart and lungs.
03:29It also provides crucial attachment points for muscles involved in respiration and upper limb
03:35movement. The sternum, or breastbone, consists of three parts, the manubrium, the body of the sternum,
03:42and the xiphoid process. Ribs 1 through 7 are classified as true ribs because they articulate
03:49directly with the sternum. Ribs 8 through 12 are known as false ribs as they either connect
03:55indirectly to the sternum or not at all.
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