Axial Skeleton
(Note: most of this material will be covered in lab)
Skull
Cranial Bones (8)
Facial Bones (14)
Cavities: Cranial, Nasal, Sinuses, Middle & Inner Ear Chambers, Orbits.
Cranium:
Frontal Bone (1). Forms superior portion of orbit; Frontal sinus.
Since it forms from two embryonic bones, it can be two bones in the adult with the "metopic suture" between left and right frontals.
Parietal (2) . Top of skull. Simple bones
Temporal (2). Complex bone. Four regions.
1.Squamous: flattened region on side of skull. Also has zygomatic process, mandibular fossa.
2.Tympanic : External auditory meatus & styloid process (site of muscle attachment).
3.Mastoid: posterior to meatus, mastoid process is a site of muscle attachment, passage for facial nerve. Has a sinus.
4.Petrous: internal; passageways for carotid artery and jugular vein.
Occipital (1). Base of skull; foramen magnum; occipital condyles (paired on side of foramen magnum); Wormian bones often formed at suture; occipital protuberance--area is site of muscle attachment.
Sphenoid (1). "Winged" bone. Spans the ventral aspect of cranium.
Sella Turcica or "Turkish Saddle" is a support for pituitary gland; numerous foramina.
Called the "keystone bone" because it articulates with all other cranial bones.
Pop Quiz: which state is called the Keystone State and why?
Ethmoid (1). Forms perpendicular plate of nasal septum; concha; passageway for olfactory nerves.
Facial Bones
* Bones of skull not in contact with brain.
* Provides basic shape of face. Teeth and muscle attachment.
Maxilla
Paired. Supports upper teeth. Alveoli = sockets.
Each maxilla has: Incisors (2), canine (1), premolars (2), molars (3).
Forms part of hard palate. Function.
Maxillary sinus.
Palatine.
Small paired bones. Forms posterior portion of hard palate (horizontal plates).
Zygomatic: Forms part of zygomatic arch with temporal bone.
Nasals: Small, paired bones = bridge of nose.
Lacrimal: Lacrimal sulcus (nasolacrimal canal--tear drainage).
Inferior nasal concha
Lateral wall of nasal cavity. Other conchae are part of ethmoid bone.
Concha = "snail" - (curved or coiled structure)
Vomer
Thin, plate-like (vomer = "plow") bone which forms part of nasal septum.
Shape is similar to blade of horse-drawn plows (image from www.usda.gov)
Other Bones of Head Region
Mandible
* Jaw bone. Supports 16 teeth which occlude with 16 teeth of 2 maxillas.
* Articulates with mandibular fossa of temporal bone..
* Body + Rami with condyloid process (jaw articulation) and coronoid process (attachment of temporalis muscle).
Hyoid
* Suspended in neck via stylohyoid ligaments.
* Body + greater and lesser cornu (horns).
* Attachment for muscles of tongue and neck muscles. Elevates when swallowing.
Middle Ear Ossicles
Malleus, Incus and Stapes.
Transfer and amplify sound impulses.
Vertebral Column
Functions
1.Support head & upper extremities while allowing movement.
2.Attachments for muscles, ribs, pectoral & pelvic girdles, and visceral structures.
3.Protect spinal cord and permit passage of spinal nerves along with some vessels.
26 movable vertebrae separated by intervertebral discs. The discs are made of fibrocartilage giving them flexibility and the ability to withstand stress.
(Intervertebral discs will be discussed in next chapter, Articulations)
33 vertebral units. 5 regions.
Cervical (7)
Thoracic (12)
Lumbar (5)
Sacral (5 fused)
Coccygeal (3-5 fused)
Curvatures: Vertebral column is S-Shaped.
*Cervical, Thoracic, Lumbar and Pelvic curvatures.
*Change during growth. Thoracic and Pelvic curvatures are "primary"
Cervical and lumbar curvatures are "secondary."
General Structure of Vertebrae:
Body (Centrum), Neural arch (supported by pedicle, arch formed by lamina). Vertebral foramen.
Processes: Spinous process, transverse processes, articular processes.
Regional Characteristics
Cervical: Transverse foramen on each side for vertebral vessels.
Atlas (C1) and axis (C2) (pivot for head).
Axis - has dens or odontoid process (for pivot joint) -- occupies area of body of axis.
Cervical Vertebra ("generic" - C3-C6): bifid spinous process
Seventh cervical vertebra (C7) has blunt spinous process (vertebral prominens)
Thoracic: Facets for rib articulations. Spinous processes point down.
Lumbar: Heavy and thick bodies. Short, blunt spinous processes.
Sacrum: Wedge shaped, 5 fused vertebrae (transverse lines are sites of fusion).
Sacroiliac articulation.Sacral promontory. Base. Apex. Sacroiliac articulation (auricular surface)
Sacrum: superior view
Coccyx: 3-5 small triangular often fused vertebrae. First coccygeal vertebra has cornua (horns).
Rib Cage
*12 Thoracic vertebrae and 12 Paired ribs
*Costal Cartilage
*Sternum
Functions:
1. Supports pectoral girdle (sternum--clavicle--scapula)
2. Protects thoracic viscera (heart & lungs)
3. Involved in breathing
4. Sternum is a site of red bone marrow.
Sternum (breastbone): 3 "separate" bones. Manubrium ("shield'), body and xiphoid process.
Manubrium has clavicular notch (sternoclavicular joint)--articulation with clavicle. Jugular notch at top.
Sternum (manubrium and body) is site for rib connection via costal cartilage.
Xiphoid process is site for abdominal muscle attachment. Last cartilage in body to ossify.
Ribs
* 12 pair. Each pair attached to 1 or 2 thoracic vertebra.
* First 7 pair are "true ribs" : They have their own costal cartilages.
* Ribs 8, 9 & 10 are "false ribs" : They share costal cartilage of rib 7.
* Ribs 11 & 12 are floating ribs: no attachment to sternum.
Note: Both men and women have 12 pairs of ribs!
(But what about the creation story in Genesis? What about Tracy and Hepburn in Adam's Rib?)
Rib structure:
*Elongate and flattened. Head, neck, angle and shaft (common to all ribs).
*Tubercle: first 10 pair have this for articulating with transverse process of thoracic vertebrae.
*Space between ribs is called the intercostal spaces; occupied by intercostal muscles.
Clinical Considerations of Axial Skeleton
Cleft Palate: incomplete fusion of palatine process of maxillary and palatine bones forming the hard palate.
* Cleft palate - case history
* Cleft lip and palate - plastic surgery
* Cleft lip/palate - severe (holoprosencephaly)
Spina bifida: Laminae of vertebra(e) do not fuse resulting in exposed spinal cord.
Abnormal Curvatures:
* Kyphosis: hunchback condition. Abnormal thoracic curvature.
* Scoliosis: Abnormal thoracolumbar curvature--lateral deviation.
* Lordosis: "swayback" or exaggerated lumbar curvature.
Cervical Ribs: Small ribs can develop from lower (typically 7th) cervical vertebrae.
Sometimes related to thoracic outlet syndrome.
APPENDICULAR SKELETON
(Note: most of this material will be covered in lab)
Pectoral Girdle & Upper Extremity.
Pelvic Girdle and Lower Extremity.
Pectoral Girdle & Upper Extremity
Pectoral girdle = 2 scapulae + 2 clavicles. Provides for muscular attachments that move the arm.
Clavicle (a.k.a., collarbone)
S-shaped. Links scapula to axial skeleton. Protects brachial plexus.
Acromial and sternal ends--sternoclavicular and acromioclavicular joints.
Conoid tuberosity or tubercle (coracoclavicular ligament attachment).
Commonly broken, especially in bicyclists.
Scapula (aka the shoulder blade). Triangular, flat bone posterior to rib cage (overlies ribs 2-7).
15 muscles attach to the scapula.
Spine on posterior surface with acromion process; also divides posterior surface into supraspinous fossa and infraspinous fossa.
Subscapular fossa on anterior surface.
Coracoid process -- muscle attachment site.
Glenoid cavity for head of humerus. Shallow ball-and-socket joint.
3 borders:
1.superior
2.medial (vertebral)
3.lateral (axillary)
Two angles: superior and inferior. (the "missing" angle is the glenoid fossa).
Brachium: or upper arm.
*Only one bone: the humerus; a long bone.
Humerus: (note -- it's not spelled humorous!!!!)
Proximal end: Head articulates with scapula at glenoid cavity.
Greater and lesser tubercles near head for muscle attachments.
Intertubercular groove for biceps tendon.
Shaft with deltoid tuberosity for attachment of deltoid muscle.
Distal end: trochlea (pulley) and capitulum.
Trochlea articulates with ulna, capitulum articulates with radius.
Coronoid fossa on anterior end, olecranon fossa on posterior end.
Lateral and medial epicondyles are sites of muscle attachments.
Ulnar nerve passes through Ôcubital tunnel" created by medial epicondyle.
"Tennis elbow" is clinically known as lateral epicondylitis.
"GolferÕs elbow" is clinically known as medial epicondylitis.
Antebrachium (forearm): 2 bones--ulna and radius, both are long bones.
Ulna--medial; Radius--lateral
Ulna
Proximal end: articulates with humerus and radius.
Olecranon process, or elbow, articulates with trochlea at semilunar notch.
Coronoid process articulates with head of radius.
Shaft: Interosseous crest for ligament attachment to radius.
Distal end: small, head has styloid process (medial portion of wrist).
Radius
Proximal end: small. Head articulates with ulna.
Shaft: upper end has radial tuberosity for attachment to biceps.
Distal end: relatively large, Lateral styloid process--at wrist.
Articulates with scaphoid (navicular) and lunate bones of wrist.
Supination and pronation of forearm made possible by radius rotating across the ulna.
Carpals: Bones of the wrist.
2 rows of 4 bones each. Cuboidal bones.
Proximal Row: Scaphoid (navicular), lunate, triquetrum, pisiform
Distal Row: Trapezium, trapezoid, capitate, hamate.
The trapezium is important for thumb movement (opposable thumb)
The scaphoid is the most commonly fractured carpal.
Pisiform is a sesamoid bone.
Metacarpals: 5 bones of the palmar area.
Small long bones. Base interfaces with carpals; shaft; head form knuckles.
I - V numbering system.
Phalanges: (Phalanx is singular) finger bones.
14 in all. 2.3.3.3.3.. Thumb only has 2 phalanges.
Divided into proximal, middle and distal phalanges.
PELVIC GIRDLE AND LOWER EXTREMITY
Functions:
Support and Locomotion
Pelvic Girdle or Pelvis(anterior, posterior)= 2 ossa coxae (hipbones).
Linked to sacrum posteriorly at sacroiliac articulation.
Linked anteriorly at symphysis pubis. Fibrocartilage.
Functions:
Supports vertebral column and keeps body upright.
Supports and protects lower viscera.
Attachment for legs (femur) -- transfers weight to femur.
Forms pelvic canal.
Each os coxa has an Ilium, Ischium and Pubis. Begin as separate bones that fuse in the adult.
Acetabulum = Òvinegar cupÓ depression formed at junction of 3 bones above, site for articulation with head of femur.
Ilium:
Largest and uppermost bone of os coxa.
Iliac crest--site for muscle attachments. Many postural muscles attach here.
2 spinous processes on anterior and posterior surfaces.
Ischium:
Lowest and strongest of pelvic bones. Ischial tuberosity bears weight of body in sitting position.
Pubis:
Anterior projecting bone. Left and right pubis are joined via symphysis pubis--a semi-moveable (amphiarthrosis) joint. Superior ramus meets ilium at acetabulum, inferior ramus meets ischium via the ramus of the ischium.
Obturator Foramen: Passageway for nerves and vessels, formed by rami of pubis and ischium.
Male Vs Female Pelvic Girdles
Adaptations are related to carrying and delivering fetus.
Female pelvis is somewhat smaller -- muscles that attach are smaller. Hips are wider and shallower than males.
"True pelvis" opening is larger in females.
Ischial tuberosity is turned more laterally in females, resulting in wider pubic arch (pubic arch in males is about 90 degrees, in females the arch is greater than 90 degrees -- the easiest feature to identify).
Other differences are found in:
Lower Extremity
Femur:
Long bone. Only bone of thigh (da thighbone's connected to .....).
The longest, heaviest and strongest bone in the body. A person's height is generally 4X femur length.
Proximal head which articulates with hipbone at acetabulum. Greater and lesser trochanters are large tuberosities for muscle attachment (thigh and buttock muscles attach.
Shaft: linea aspera -- site of muscle insertion.
Distal end: Medial and lateral condyles articulate with tibia and patella. Lateral and medial epicondyles provide ligament attachments. Anterior surface has flattened region for interface of patella (patellar surface).
Patella or kneecap
A sesamoid bone: within the quadriceps femoris tendon. Protects knee and allows for more leverage for quads. Triangular bone with upper base and lower apex. Posterior facets for articulation with condyles of femur.
Lower Leg: Tibia (medial) and Fibula (lateral)
Tibia = shinbone.
A long bone. Similar to femur in length, strength and density. Supports weight and transfers force to foot (talus).
Proximal end: Lateral and medial condyles which articulate with lateral and medial condyles of femur.
Tibial tuberosity for patellar ligament attachment. Articulation with head of fibula.
Shaft: anterior crest.
Distal end: expanded in the form of medial malleolus. Articulation with talus of foot. Articulation with fibula.
Note: stress fractures of tibia can feel like a "shinsplint," but are distinctly different.
Fibula:
parallels tibia, but much thinner. For muscle attachment, little weight bearing role.
Proximal = head, which articulates with tibia.
Shaft = long and thin--no remarkable features.
Distal = has lateral malleolus.
The fibula is often used for transplantation -- serves as graft to replace damaged long bones (other source on grafting)
Ankle and Foot:
Tarsus (7 bones) , Metatarsus (5 bones) and Phalanges (14 bones) per leg.
Tarsus: 7 short or cuboidal bones.
Talus: articulates with tibia to form ankle joint. Distributes force of upper leg to foot.
Calcaneus: heel bone. largest tarsal bone. Receives 1/2 of force from talus.
Site of ligament attachment (calf muscles).
Navicular, cuboid and 3 cuneiforms make up rest of tarsus.
Metatarsals: Form sole of foot. 1 bone per toe.
Small, long bones with base (tarsal interface), shaft, and head (phalanges interface).
Numbered 1-5 (I Ð V) medial to lateral.
Phalanges: bones that make up toes. Numbering system as for hand.
Phalanges are similar to those of hand, just shorter and thicker.
Big toe is not opposable.
Arches of feet: Longitudinal and transverse curves formed by angle between tarsals and metatarsals.
Provide support and leverage for walking. Bones are held together by ligaments which provide "spring" in step.
Weakened ligaments result in "fallen arches" or "flat feet."
Developmental Conditions of Appendicular Skeleton
Syndactyly: Genetic. Webbed digits
Polydactyly: Genetic. Extra digits present (fingers or toes)
Clubfoot (talipes): congenital condition in which foot is twisted medially.