The Vertebrate Skeleton A vertebrate skeleton is divided into an axial and appendicular skeleton. The axial skeleton protects the organs of the head, neck and chest. The appendicular skeleton includes the bones of the limbs.
The axial skeleton consists of the 80 bones in the head and trunk of the human body. It is composed of five parts; the human skull, the ossicles of the middle ear, the hyoid bone of the throat, the rib cage, and the vertebral column. The axial skeleton and the appendicular skeleton together form the complete skeleton and the sternum.
Overview Flat bones house the brain, spinal cord, and other vital organs. This article mainly deals with the axial skeletons of humans; however, it is important to understand the evolutionary lineage of the axial skeleton. The human axial skeleton consists of 80 different bones. As the skeleton grows older the bones get weaker with the exception of the skull. The skull remains strong so as to protect the brain from injury.
Skull Human skull Skull (22) • Cranial Bones (8) • Parietal (2) • Temporal (2) • Frontal (1) • Occipital (1) • Ethmoid (1) • Sphenoid (1) • Facial Bones (14) • Maxilla (2) • Zygomatic (2) • Mandible (1) • Nasal (2) • Palatine (2) • Inferior nasal concha (2) • Lacrimal (2) • Vomer (1
Auditory Ossicles Ossicles (6 ) • Malleus (2) • Incus (2) • Stapes (2) Hyoid bone Hyoid bone (1) U-shape bone located in the neck. It anchors the tongue and is associated with swallowing.
Vertebral column Main article: Vertebral column Vertebral Column (26) • Cervical vertebrae (7) • Thoracic vertebrae (12) • Lumbar vertebrae (5) • Sacrum (1) (they are 5 but fused in adult stage) • Coccyx (1) (they are 4 but fused to form one single bone, varies between 3-5)
Chest Main article: Chest Thoracic cage (25) • Sternum (1) • Ribs (24)
The appendicular skeleton is composed of 126 bones in the human body. The word appendicular is the adjective of the noun appendage, hich itself means a part that is joined to something larger. Functionally it is involved in locomotion (Lower limbs) of the axial skeleton and manipulation of objects in the environment (Upper limbs).
The appendicular skeleton is divided into six major regions: 1) Pectoral Girdles (4 bones) - Left and right Clavicle (2) and Scapula (2). 2) Arm and Forearm (6 bones) - Left and right Humerus (2) (Arm), Ulna (2) and Radius (2) (Fore Arm). 3) Hands (58 bones) - Left and right Carpal (16) (wrist), Metacarpal (10), Proximal phalanges (10), Middle phalanges (8), distal phalanges (10), and sesamoid (4). 4) Pelvis (2 bones) - Left and right oscoxae (2) (ilium). 5) Thigh and leg (8 bones) - Femur (2) (thigh), Tibia (2), Patella (2) (knee), and Fibula (2) (leg). 6) Feet (56 bones) - Tarsals (14) (ankle), Metatarsals (10), Proximal phalanges (10), middle phalanges (8), distal phalanges (10), and sesamoid (4).
It is important to realize that through anatomical variation it is common for the skeleton to have many extra bones (sutural bones in the skull, cervical ribs, lumbar ribs and even extra lumbar vertebrae) The appendicular skeleton of 126 bones and the axial skeleton of 80 bones together form the complete skeleton of 206 bones in the human body. Unlike the axial skeleton, the appendicular skeleton is unfused. This allows for a much greater range of motion