Chapter 7: Comparison of the Axial and Appendicular Skeletons PDF

7.1 Comparison of the Axial and Appendicular Skeletons The human skeleton can be divided into two primary structural divisions: the axial skeleton and the appendicular skeleton. Below, you'll find a comparison of these two divisions, along with a brief overview of their functions and key component...

7.1 Comparison of the Axial and Appendicular Skeletons The human skeleton can be divided into two primary structural divisions: the axial skeleton and the appendicular skeleton. Below, you'll find a comparison of these two divisions, along with a brief overview of their functions and key components: Axial Skeleton Definition: The axial skeleton forms the longitudinal axis of the body. Components: o Skull: Comprises cranial and facial bones; protects the brain and forms the face. o Vertebral Column: Made up of approximately 24 individual vertebrae, the sacrum, and the coccyx; encases the spinal cord. o Thoracic Cage: Consists of the sternum and 12 pairs of ribs; protects thoracic organs such as the heart and lungs. Function: o Protection: Provides a protective casing for the brain, spinal cord, and thoracic organs. o Support: Serves as a structural backbone for the body, enhancing stability. o Attachment: Establishes points of attachment for muscles and ligaments. Appendicular Skeleton Definition: The appendicular skeleton involves the bones of the upper and lower limbs, along with the pectoral (shoulder) and pelvic (hip) girdles. Components: o Pectoral Girdle: Composed of the clavicle and scapula; connects upper limbs to the torso. o Upper Limbs: Includes the humerus, radius, ulna, carpals, metacarpals, and phalanges. o Pelvic Girdle: Formed by the hip bones, which are fused structures that provide support for the lower limbs.  o Lower Limbs: Comprises the femur, patella, tibia, fibula, tarsals, metatarsals, and phalanges. Function: o Movement: Facilitates motion and enables a wide range of activities from walking to grasping. o Support: Provides support for the limbs and serves as leverage for muscle action. o Attachment: Provides anchorage points for muscles necessary for mobility. Summary of Major Bones of the Skeleton The skull consists of Frontal, parietal, temporal, occipital, sphenoid, ethmoid (cranial bones); mandible, maxilla, nasal, lacrimal, zygomatic, palatine, vomer, inferior nasal conchae (facial bones). The vertebral column consists of cervical, thoracic, lumbar vertebrae, sacrum, and coccyx. The thoracic cage includes ribs and sternum. The pectoral girdle consists of the clavicle and scapula. The upper limb encompasses bones such as the humerus, radius, and ulna. The pelvic girdle includes hip bones formed from the fusion of ilium, ischium, and pubis. The lower limb includes the femur, patella, tibia, fibula, tarsals, metatarsals, and phalanges. Summary of Cartilaginous Components Cartilage Types: o Hyaline Cartilage: Found at the ends of long bones and at joints, as well as in the ribs and the epiphyseal plates of growing bones. o Fibrocartilage: Provides strength and can be found in intervertebral discs and the pubic symphysis. 7.2 (play skull/facial bones game) Cranial Bones The skull consists of eight cranial bones, which are: 1. Frontal Bone: o Location: Forms the forehead and the superior parts of the orbits (eye sockets). o Structural Features: Contains the frontal sinus, has a smooth glabella, and the supraorbital foramen for nerves and blood vessels. o Functions: Protects the frontal lobes of the brain and forms a part of the orbit. 2. Parietal Bones (2): o Location: Form the superior and lateral aspects of the skull. o Structural Features: Each parietal bone articulates with the frontal bone at the coronal suture, occipital bone at the lambdoid suture, and temporal bones at the squamous suture. o Functions: Enclose and protect the brain and provide surfaces for muscle attachment. 3. Occipital Bone: o Location: Forms the posterior base of the skull. o Structural Features: Contains the foramen magnum (where the spinal cord exits), occipital condyles (articulate with the cervical vertebra), and external occipital protuberance. o Functions: Protects the brain and serves as a connection point for the vertebral column. 4. Temporal Bones (2): o Location: Located at the sides and base of the skull.  o Structural Features: Each has several regions (squamous, tympanic, mastoid, and petrous), and contains the mandibular fossa, external acoustic meatus, and mastoid process. o Functions: Protect the temporal lobes of the brain and support structures of hearing. 5. Sphenoid Bone: o Location: Centrally located at the base of the skull, resembling a butterfly. o Structural Features: Contains the sella turcica (housing the pituitary gland), and has greater and lesser wings. o Functions: Connects the cranial base with facial bones and enclose the entrance to the cranial cavity. 6. Ethmoid Bone: o Location: Located between the eyes and forms part of the nasal cavity. o Structural Features: Features the cribriform plate, perpendicular plate (part of the nasal septum), and ethmoidal sinuses. o Functions: Contributes to the structure of the nasal cavity and orbits, and supports the olfactory system. Main Sutures Coronal Suture: Joint between the frontal bone and the parietal bones. Sagittal Suture: Joint between the two parietal bones. Lambdoid Suture: Joint between the occipital bone and the parietal bones. Squamous Suture: Joint between temporal bones and parietal bones. These sutures are fibrous joints that provide stability to the skull while allowing for slight movement during growth, particularly in infancy. Facial Bones The facial skeleton has 14 bones, which include: 1. Maxillae (2): o Location: Upper jaw and part of the orbits.  o Structural Features: Contains maxillary sinuses and alveolar processes for teeth. o Functions: Forms the anterior part of the hard palate and supports upper teeth. 2. Mandible: o Location: Lower jaw. o Structural Features: U-shaped with a body, two rami, and articulates with the temporal bone at the temporomandibular joint (TMJ). o Functions: Holds lower teeth and is movable, allowing for chewing and speaking. 3. Zygomatic Bones (2): o Location: Cheekbones. o Structural Features: Contributes to the lateral wall and floor of the orbit. o Functions: Provides structure to the face and supports the eyes. 4. Nasal Bones (2): o Location: Bridge of the nose. o Structural Features: Small and oblong. o Functions: Support the structure of the nose. 5. Lacrimal Bones (2): o Location: Medial wall of the orbit. o Structural Features: Contains the lacrimal fossa for the lacrimal sac. o Functions: Involved in the drainage of tears. 6. Palatine Bones (2): o Location: Form the posterior part of the hard palate. o Structural Features: L-shaped with horizontal and vertical plates. o Functions: Support the hard palate and part of the nasal cavity. 7. Inferior Nasal Conchae (2):  o Location: Lateral walls of the nasal cavity. o Structural Features: Scroll-like bones. o Functions: Increase the surface area for air filtration and humidification. 8. Vomer: o Location: Forms the inferior part of the nasal septum. o Structural Features: Plow-shaped. o Functions: Divides the nasal cavity. Hyoid Bone The hyoid bone is a unique bone located in the superior neck. Location: Situated just below the mandible and above the larynx. Structural Features: U-shaped with a body, greater cornua, and lesser cornua; does not articulate directly with any other bone. Does not articulate with others. Functions: Supports the tongue, serves as an attachment for muscles involved in swallowing and speech, and is important in forensic analysis as a broken hyoid can indicate strangulation. Cavities of the Skull Cavities and sinuses game 1. Orbit Location: Bony cavity surrounding the eyeball. Structural Features: Formed by seven bones (frontal, maxilla, zygomatic, sphenoid, ethmoid, lacrimal, and palatine). Functions: Houses the eyeball and connective structures (muscles, nerves, blood vessels) for vision. 2. Nasal Cavity Location: Air-filled space above the roof of the mouth. Structural Features: Formed by several bones, including the frontal, maxilla, ethmoid, and the nasal bones. It features the nasal septum.  Functions: Warms, humidifies, and filters air; supports olfactory receptors; contributes to voice resonance. 3. Paranasal Sinuses Location: Hollow cavities in the facial bones that include the frontal, maxillary, ethmoidal, and sphenoidal sinuses. Structural Features: Lined with mucous membrane; communicate with the nasal cavity. Functions: Lighten the skull, improve voice resonance, and provide mucous drainage.  axial Skull: o Cranial Bones: Frontal, parietal, temporal, occipital, sphenoid, and ethmoid. o Facial Bones: Nasal bones, maxillae, zygomatic bones, mandible, palatine bones, lunate bones, and inferior nasal conchae. Vertebral Column: o Consists of 24 individual vertebrae: cervical vertebrae (C1-C7), thoracic vertebrae (T1-T12), and lumbar vertebrae (L1-L5). o Sacrum: A single triangular bone formed by the fusion of five sacral vertebrae. o Coccyx: A small, triangular bone made up of four fused vertebrae, also known as the tailbone. Thoracic Cage: o Sternum: Comprises the manubrium, body, and xiphoid process. o Ribs: 12 pairs, including true ribs (ribs 1-7), false ribs (ribs 8-10), and floating ribs (ribs 11-12). appendicular o Pectoral Girdle: ▪ Clavicle: The collarbone that connects the arm to the body. ▪ Scapula: Also known as the shoulder blade. o Upper Limbs: ▪ Humerus: The bone of the upper arm. ▪ Radius: The lateral bone of the forearm (thumb side).  ▪ Ulna: The medial bone of the forearm (pinky side). ▪ Carpals: Eight wrist bones (scaphoid, lunate, triquetrum, pisiform, trapezium, trapezoid, capitate, hamate). ▪ Metacarpals: Five bones forming the palm of the hand. ▪ Phalanges: 14 bones in the fingers (three in each finger and two in each thumb). o Pelvic Girdle: ▪ Consists of two hip bones (coxal bones) that are each made up of three fused bones: ilium, ischium, and pubis. o Lower Limbs: ▪ Femur: The thigh bone, the longest bone in the body. ▪ Patella: The kneecap. ▪ Tibia: The larger shin bone, also known as the shinbone, medial side. ▪ Fibula: The smaller bone of the lower leg, lateral side. ▪ Tarsals: Seven ankle bones (talus, calcaneus, navicular, medial cuneiform, intermediate cuneiform, lateral cuneiform, and cuboid). ▪ Metatarsals: Five bones that form the middle part of the foot. ▪ Phalanges: 14 bones in the toes (three in each toe and two in each big toe).  7.5 The anatomy of the pelvic bones in adult males and females reflects their different roles in human physiology, particularly during childbirth. Here, I will outline the key differences and similarities between male and female pelves, focusing on structural features and functionality: General Differences 1. Overall Shape: o Female Pelvis: Wider and shallower, adapted for childbirth. The greater pelvis is larger and more flared. o Male Pelvis: Narrower and deeper, with a more compact structure. 2. Pelvic Inlet: o Female Pelvis: Usually oval and larger in area. The pelvic inlet is wider to facilitate childbirth. o Male Pelvis: Generally heart-shaped and narrower, reflecting a structure that is less adapted for childbirth. 3. Pelvic Outlet: o Female Pelvis: Wider due to the more significant distance between the ischial tuberosities. o Male Pelvis: Narrower outlet, limiting passage during childbirth. 4. Acetabula: o Female Acetabula: Relatively far apart and oriented more anteriorly. This contributes to a wider stance during walking. o Male Acetabula: Closer together and oriented laterally, reflecting a more upright posture and gait. 5. Pubic Arch: o Female Pelvis: The angle of the pubic arch is wider, typically ranging from 90 to 100 degrees. o Male Pelvis: The pubic arch has a narrower angle, generally between 60 and 70 degrees. 6. Sacrum: o Female Sacrum: Shorter, wider, and more curved to accommodate the pelvic inlet and outlet dimensions. o Male Sacrum: Longer, narrower, and more straight, contributing to a more vertical pelvis. 7. Coccyx: o Female Coccyx: More posteriorly positioned and movable. A more anterior coccyx can increase the risk of fractures during childbirth. o Male Coccyx: Tends to be shorter and less flexible, oriented more vertically. 8. Ischial Tuberosities: o Female Pelvis: Ischial tuberosities point laterally, giving the female pelvis a broader appearance. o Male Pelvis: Ischial tuberosities point medially, contributing to a narrower appearance. 9. Weight and Robustness: o Female Pelvis: Lighter and less robust, reflecting adaptation for childbirth. o Male Pelvis: Heavier and more robust due to greater muscle attachment sites and activity-related adaptations. Similarities 1. Basic Bone Structure: Both male and female pelves consist of the same three bone components: the ilium, ischium, and pubis, which fuse to form the os coxae. 2. Functions: Both serve primary functions in bearing weight, supporting the organs of the pelvis, and anchoring the lower limbs to the axial skeleton. 3. Common Conditions: Both sexes can experience similar pelvic conditions, such as fractures or arthritis, despite anatomical differences. 4. Ligament and Muscle Attachments: Both pelves exhibit similar sites for muscle and ligament attachments, though the size and robustness may vary.