Easy Notes Chapter 7-8 skeletal system
Chapter 7
Purpose of Axial Skeleton
Provides main support for the body and protects vital organs.
Bones in Axial Skeleton
Adult Human Skeleton Total: 206 named bones.
Axial Skeleton: 80 bones, including:
Skull: 22 bones (8 cranial, 14 facial)
Hyoid Bone: 1 bone (supports the tongue and provides attachment for neck muscles)
Auditory Ossicles: 6 bones (3 in each ear, responsible for sound transmission)
Vertebral Column: 26 bones (composed of vertebrae)
Thorax: 1 sternum and 24 ribs (protects heart and lungs)
5 Different Shapes of Bones
Long Bones: Bones that are longer than they are wide (e.g., femur).
Short Bones: Roughly cube-shaped bones (e.g., carpals).
Flat Bones: Bones composed of thin layers of parallel plates (e.g., skull bones).
Irregular Bones: Complex shaped bones that do not fit into other categories (e.g., vertebrae).
Sesamoid Bones: Bones shaped like sesame seeds, found in tendons (e.g., patella).
Bones of the Skull
Total: Contains 22 bones (excluding the 6 auditory ossicles).
Cranial Bones: Frontal, parietal (2), temporal (2), occipital, sphenoid, ethmoid.
Facial Bones: Nasal (2), maxillae (2), zygomatic (2), mandible (1), lacrimal (2), palatine (2), inferior nasal conchae (2), vomer (1).
Bones of the Vertebral Column
Composed of 26 vertebrae divided into 5 regions:
Cervical (7): Bones of the neck.
Thoracic (12): Bones of the upper back, each articulating with ribs.
Lumbar (5): Bones of the lower back, supporting most body weight.
Sacrum (1): Formed from the fusion of 5 sacral vertebrae.
Coccyx (1): Formed from the fusion of 4 coccygeal vertebrae.
Unique Features of Vertebrae
Cervical: Smallest, bifid (split) spinous processes; Atlas (C1) lacks a body and spinous process; Axis (C2) has a dens for head rotation.
Thoracic: Larger bodies than cervical; presence of costal facets for rib articulation.
Lumbar: Thickest and largest vertebrae with robust spinous processes.
Bones of the Rib Cage
Consists of 12 pairs of ribs:
True Ribs (1-7): Directly connect to the sternum via their own costal cartilage.
False Ribs (8-12): Do not attach directly to the sternum (8-10 connect indirectly via the cartilage of rib 7).
Floating Ribs (11-12): Do not attach to the sternum at all.
Parts of the Sternum
Manubrium: The upper part of the sternum.
Body: The middle portion of the sternum.
Xiphoid Process: The small, cartilaginous lower end of the sternum.
Depressions and Openings
Major types include:
Fissures: Narrow slits between adjacent bones.
Foramina: Holes allowing passage for nerves and vessels.
Fossae: Shallow depressions for muscle attachment or joint articulation.
Sulci: Grooves along a bone surface for soft tissue accommodation.
Meatuses: Tube-like passages through a bone.
Function: Allow passage of soft tissues or help form joints.
Processes
Major types include:
Condyles: Enlarged ends that form joints (e.g., femoral condyles).
Facets: Smooth, flat surfaces for articulation (e.g., vertebral facets).
Heads: Rounded projections at the end of a bone (e.g., femoral head).
Crests: Prominent ridges for muscle attachment (e.g., iliac crest).
Epicondyles: Rough projections above condyles for ligament attachment (e.g., medial epicondyle of the femur).
Lines (Linea): Narrow ridges less prominent than crests (e.g., linea aspera).
Spinous Processes: Sharp projections for muscle attachment (e.g., vertebrae).
Trochanters: Large projections on the femur (e.g., greater and lesser trochanters).
Tubercles: Round projections (e.g., greater tubercle of the humerus).
Tuberosities: Variously sized rough projections (e.g., ischial tuberosity).
Function: Projections for joint formation or attachment for ligaments and tendons.
Dysfunctions of the Axial Skeleton
Common problems include:
Herniated Discs: Protrusion of the nucleus pulposus.
Scoliosis: Abnormal lateral curvature of the spine.
Kyphosis: Increased thoracic curve (hunchback appearance).
Lordosis: Increased lumbar curve (swayback appearance).
Spina Bifida: A congenital defect where the laminae of the vertebrae fail to develop normally.
Vertebral Fractures: Commonly occur at specific vertebrae levels with potential spinal cord damage.
Facial Bones
Total: 14 bones including nasal (2), maxillae (2), zygomatic (2), mandible (1), lacrimal (2), palatine (2), inferior nasal conchae (2), and vomer (1).
Why is the Mandible Special?
The mandible is the largest, strongest, and the only movable bone of the skull (excluding auditory ossicles).
Nasal Septum Components
Composed of vomer (bone), perpendicular plate of the ethmoid (bone), and cartilage.
Major Foramina of the Skull
Key foramina include:
Carotid Canal: Transmits the internal carotid artery.
Hypoglossal Canal: Transmits the hypoglossal nerve (CN XII).
Jugular Foramen: Transmits the internal jugular vein and cranial nerves IX, X, and XI.
Foramen Magnum: Connects cranial cavity to vertebral canal; transmits the medulla oblongata.
Four Paranasal Sinuses
Sinuses Include:
Frontal Sinus: In the frontal bone, above the eyes.
Maxillary Sinus: Largest, located in the maxilla.
Sphenoid Sinus: In the sphenoid bone, behind the eyes.
Ethmoid Sinus: Located between the nose and eyes.
Function: Act as resonating chambers for voice, increasing nasal mucosa surface area.
Fetal Skull Fontanels
Areas of unossified mesenchyme (soft spots) that allow for brain growth; close by age 2.
Hyoid Bone
A unique bone that does not articulate with others; supports the tongue and provides attachment for neck muscles.
Parts of the Vertebral Column
Consists of cervical, thoracic, lumbar regions, sacrum, and coccyx.
Curvatures of the Vertebral Column
Curvatures: Anteriorly concave fetal curvature; adults possess cervical, thoracic, lumbar, and sacral curves.
Intervertebral Discs
Fibrocartilaginous discs providing cushioning between vertebrae, composed of an outer annulus fibrosus and inner nucleus pulposus.
Unique Vertebrae
C1 (Atlas):
Unique Feature: Lacks a body and spinous process.
Function: Allows nodding of the head (flexion and extension).
C2 (Axis):
Unique Feature: Contains the dens (odontoid process).
Function: Permits rotation of the head by acting as a pivot.
Differences Between Vertebrae Types
Cervical Vertebrae:
Size: Smallest vertebrae.
Foramina: One vertebral foramen and two transverse foramina.
Spinous Process: Slender and often bifid (split) from C2 to C6.
Thoracic Vertebrae:
Size: Larger than cervical vertebrae.
Foramina: One vertebral foramen.
Spinous Process: Long, fairly thick, projecting inferiorly.
Unique Features: Presence of costal facets for rib articulation.
Lumbar Vertebrae:
Size: Largest and strongest.
Foramina: One vertebral foramen.
Spinous Process: Short and blunt, projects posteriorly.
Discs: Thickest intervertebral discs, supporting most body weight.
Sacrum
Structure: Formed by the fusion of five sacral vertebrae.
Function: Connects the spine to the hip bones, providing strength and stability.
Coccyx
Structure: Formed from the fusion of four coccygeal vertebrae.
Function: Forms the tailbone and serves as an attachment site for ligaments and muscles.
Herniated Disc
Definition: Protrusion of the nucleus pulposus through the annulus fibrosus, often due to trauma or aging.
Symptoms: Pain, numbness, or weakness in the affected area or down the limbs.
Disorders of the Vertebral Column
Scoliosis: Abnormal lateral curvature of the spine.
Kyphosis: Increased thoracic curve (hunchback appearance).
Lordosis: Increased lumbar curve (swayback appearance).
Spina Bifida: A congenital defect where the laminae of the vertebrae fail to develop normally.
Vertebral Fractures: Commonly occur at specific vertebrae levels with potential for spinal cord damage.
Chapter 8 Appendicular Skeleton:
Pectoral Girdle
Composed of the clavicles (collarbones) and scapulae (shoulder blades).
Functions to connect the upper limb to the trunk and support arm movements.
Pelvic Girdle
Composed of the hip bones (coxal bones).
Functions to support the weight of the body during sitting and standing, protect pelvic organs, and form the birth canal in females.
Parts of the Clavicle
Sternal End: Connects to the sternum.
Acromial End: Connects to the acromion of the scapula.
Conoid Tubercle: Serves as an attachment point for ligaments.
Articulations Between Bones of the Appendicular Skeleton
Ball-and-socket joints (e.g., shoulder and hip joints).
Hinge joints (e.g., elbow and knee joints).
Pivot joints (e.g., between radius and ulna).
Parts of the Scapula
Spine: Prominent ridge on the posterior side.
Acromion: An extension of the spine that forms a joint with the clavicle.
Glenoid cavity: Socket for the head of the humerus.
Parts of the Humerus
Head: Round proximal end that fits into the glenoid cavity.
Greater and Lesser Tubercle: Provide attachment sites for rotator cuff muscles.
Shaft: Long central part of the bone.
Condyles: Include the capitulum and trochlea for articulation with the forearm.
Parts of the Radius and Ulna
Radius: Thinner bone on the lateral side of the forearm; includes the radial head and styloid process.
Ulna: Thicker bone on the medial side; includes the olecranon (elbow) and styloid process.
Carpal Bones, Metacarpals, and Phalanges
Carpal Bones: 8 bones in the wrist; arranged in two rows: proximal (scaphoid, lunate, triquetrum, pisiform) and distal (trapezium, trapezoid, capitate, hamate).
Metacarpals: 5 bones forming the palm of the hand.
Phalanges: 14 bones in the fingers; 3 in each finger (proximal, middle, distal) and 2 in the thumb (proximal, distal).
Parts of the Hip
Ilium: Largest part; includes the iliac crest.
Ischium: Lower part; forms the sit bone.
Pubis: Anterior part that meets at the pubic symphysis.
Parts of the Femur
Head: Round proximal end articulating with the acetabulum of the hip.
Neck: Narrow area just below the head.
Greater and Lesser Trochanters: Projections for muscle attachment.
Condyles: Medial and lateral condyles at the distal end for knee joint articulation.
Parts of the Tibia and Fibula
Tibia: Larger weight-bearing bone; includes the tibial tuberosity, medial malleolus, and lateral malleolus (the ankle).
Fibula: Thinner bone; mainly provides support and stability.
Tarsal Bones, Metatarsals, and Phalanges
Tarsal Bones: 7 bones in the ankle (e.g., talus, calcaneus).
Metatarsals: 5 bones forming the arch of the foot.
Phalanges: 14 bones in the toes; similar to fingers with each toe having three (proximal, middle, distal) except for the big toe.
Arches of the Foot
Medial Longitudinal Arch: Highest arch running from heel to toe.
Lateral Longitudinal Arch: Lower arch, also from heel to toe.
Transverse Arch: Crosswise arch at the proximal part of the metatarsals.
Skeletal Tissue in Fetal Development
Initially composed mostly of hyaline cartilage which later ossifies into bone during growth.
Development of Bones of the Face
Includes the mandible, zygomatic bones, nasal bones, and maxilla; primarily formed from intramembranous ossification.
Development of Bones of the Skull
Formed by a combination of intramembranous and endochondral ossification leading to the cranial vault and base development.
Development of Bones of the Limbs
Limb bones develop through endochondral ossification from cartilage models, shaping into long bones.
False (Greater) Pelvis vs. True (Lesser) Pelvis
False Pelvis: Superior part of the pelvis; supports the intestines.
True Pelvis: Inferior part; defines the birth canal.
Differences Between the Male and Female Pelves
Male pelvis: Narrower, heavier, and deeper for bipedal locomotion.
Female pelvis: Wider, lighter, and broader for childbirth.