Anatomy & Physiology Honors
Unit 2: Protection, Support & Movement
Chapters 6 – 8: Skeletal System
CLE3251.2.1: IDY the structures of the skeletal system and show the relationship between these structures and
their functions.
CLE3251.2.2: Investigate the physiological mechanisms that allow the skeletal system to function.
Objectives:
Distinguish between the different types of bones.
Describe the physiological mechanisms involved in bone development, growth, and repair.
Compare and contrast the axial and appendicular skeletons using a graphic organizer.
The skeletal system includes: bones, cartilages, ligaments, and other connective tissues that stabilize or
interconnect the bones.
Section 6.1: Five Primary Functions of the skeletal system
1. Structural support for attachment of soft tissues and organs
2. Storage of minerals and lipids in bone and yellow marrow
3. Blood cell production in red marrow, which fills the internal cavities of many bones
4. Protection of soft tissues and organs
a. Rib cage – heart and lungs
b. Skull – brain
c. Vertebrae – spinal cord
d. Pelvis – digestive and reproductive organs
5. Leverage that can change the magnitude and forces generated by skeletal muscles
Section 6.2: Bone classifications
Bones are classified in two ways:
1. Bone structure and shape:
a. Long bones – arm, forearm, thigh, leg, palms, soles, fingers and toes
b. Flat bones – roof of skull, sternum, ribs, scapulae – provide protection for underlying soft tissues
and offer extensive surface area for the attachment of skeletal muscles
c. Sutural bones – (AKA Wormian bones) small, flat, irregularly shaped bones between the flat bones
of the skull
d. Irregular bones – have complex shapes with short, flat, notched, or ridged surfaces –spinal
vertebrae, pelvic bones, several skull bones
e. Short bones – carpal bones (wrists) and tarsal bones (ankles)
f. Sesamoid bones – small, flat bones somewhat shaped like a sesame seed – found in almost 26
different locations of the body, usually near joints of knees, hands, and feet – kneecaps (sesamoid
patellae
2. Bone markings / surface features:
a. Elevations and projections
i. Process – any projection or bump
ii. Ramus – An extension of a bone making an ankle with the rest of the structure
b. Processes formed where tendons or ligaments attach
i. Trochanter – a large, rough projection
ii. Tuberosity – a smaller rough projection
iii. Tubercle – a small rounded projection
iv. Crest – A prominent ridge
v. Line – a low ridge
vi. Spine – a pointed or narrow process
c. Processes formed for articulation with adjacent bones
i. Head – expanded articular end of an epiphysis, separated from the shaft by a neck
ii. Neck – a narrow connection between the epiphysis and the diaphysis
iii. Condoyle – a smooth rounded articular process
iv. Trochlea – a smooth grooved articular process shaped like a pulley
v. Facet – a small, flat articular surface
d. Depressions
i. Fossa – a shallow depression
ii. Sulcus – a narrow groove
e. Openings
i. Foramen – rounded passageway for blood vessels or nerves
ii. Canal or meatus – passageway through the substance of a bone
iii. Fissure – an elongated cleft
iv. Sinus or antrum – chamber within a bone, normally filled with air
Diaphysis: an extended tubular shaft
Epiphysis: an expanded area at the ends of a bone
Section 6.5: Ossification and appositional growth are mechanisms of bone formation and enlargement
Osteogenesis: the physical process of bone formation and growth
Ossification: the process of replacing other tissues with bone
Calcification: the deposition of calcium salts that occurs during ossification
Osseous tissue is highly vascular, because growing bones require an extensive blood supply.
Section 6.7: Exercise, hormones, and nutrition affect bone development and the skeletal system
If you don’t use it, you will lose it! The stresses applied to bones during physical activity are essential to maintaining
bone strength and bone mass. Degenerative changes in the skeleton occur after relatively brief periods of inactivity.
Normal bone growth and maintenance also depend on the following nutritional and hormonal factors:
 A constant dietary source of calcium and phosphate salts, and smaller amounts of magnesium, fluoride,
iron, and manganese
 Calcitrol (synthesized in the kidneys) for calcium and phosphate ion absorption
 Vitamin C stimulates osteoblast differentiation – Scurvy is a loss of bone mass and strength
 Vitamins A (stimulates osteoblast activity), K and B₁₂ (required for protein synthesis in bone)
 Growth hormone and thyoxine for bone growth and protein synthesis
 At puberty, sex hormones (estrogens in females and androgens in males) for bone ossification and
maturation
The skeletal system is unique in that it persists after life, providing clues to the sex, lifestyle, and environmental
conditions experienced by the individual. Not only do the bones reflect the physical stresses placed on the body,
but they also provide clues concerning the person’s health and diet, including features that are characteristic to
hormonal deficiencies.
Section 6.9: Bone fractures
Classifications of bone fractures:
1. Simple fractures (AKA Closed) – completely internal, and can only be seen on x-rays because they do not
involve a break in the skin; usually relatively simple to treat, because the surrounding tissues keep the
broken ends of the bone aligned
2. Compound fractures (AKA Open) – project through the skin and are obvious on inspection; also more
dangerous due to the possibility of infection or incontrollable bleeding.
3. Transverse fracture: involves a break at right angles to the long axis of a bone
4. Comminuted fracture: involves a shattering of the affected bone(s)
5. Pott fracture – occurs at the ankle and affects both bones of the leg
6. Spiral fractures – produced by twisting stresses that spread along the length of the bone
7. Displaced fractures – produce new and abnormal bone arrangements
8. Nondisplaced fractures – retain the normal alignment of the bones or fragments
9. Colles fracture – a break in the distal portion of the radius, typically as a result of reaching out to cushion a
fall
10. Greenstick fracture – when only one side of the bone shaft is broken, and the other is bent; generally
occurs in children, whose long bones have not fully ossified
11. Epiphyseal fracture – tends to occur where the bone matrix is undergoing calcification; if not treated
promptly and correctly, these fractures can permanently stop growth at site of fracture
12. Compression fracture – occur in vertebrae subjected to extreme stresses, such as falling down
Chapter 7 – The Axial skeleton
Section 7.1: Axial Skeleton contains 80 bones
Axial skeleton – the collection of bones that form the longitudinal axis of the body, containing 80 bones (roughly
40% of the bones in the human body.
Components of the axial skeleton:
 Skull – 8 cranial bones and 14 facial bones
 Auxiliary skull – 6 auditory ossicles and the hyoid bone
 Vertebral column – 24 vertebrae, sacrum, coccyx
 Thoracic cage – sternum and 24 ribs
Section 7.2: Skull bones
Occipital
Cranial Bones
Forms much of the posterior and inferior
surfaces of the cranium
Maxillae /
Maxillary
Parietal
Forms part of the superior and lateral
surfaces of the cranium
Palatine
Frontal
Forms the anterior portion of the
cranium and the roof of the orbis (eye
sockets).
Mucus secretions of the frontal sinuses
within this bone help flush the surfaces
of the nasal cavities
Form part of both the lateral walls of the
cranium and the zygomatic arches
Form the only articulations with the
mandible
Surround and protect the sense organs
of the inner ear
Are attachment sites for muscles that
close the jaws and move the head
Forms part of the floor of the cranium,
unites the cranial and facial bones, and
acts as a cross brace that strengthens the
sides of the skull. Mucous secretions of
the sphenoidal sinuses help clean the
surfaces of the nasal cavities.
Forms the anteromedial floor of the
cranium, the roof of the nasal caviy, and
part of the nasal septum and medial
orbital wall. Mucous secretions from a
network of sinuses, or ethmoidal air cells
flush the surfaces of the nasal cavities
Nasal
Temporal
Sphenoid
Ethmoid
Facial Bones
Support the upper teeth and form the
inner orbital rim, the upper jaw, and
most of the hard palate. Largest facial
bones
Form the posterior portion of the hard
palate and contribute to the floor of
each orbit
Support the superior portion of the
bridge of the nose
Vomer
Forms the inferior portion of the bony
nasal septum
Inferior nasal
conchae
Creates turbulence in air passing
through the nasal cavity and increases
the epithelial surface area to promote
warming and humidification of inhaled
air
Zygomatic
Contributes to the rim and lateral wall
of the orbit and form part of the
zygomatic arch
Lacrimal
Form part of the medial wall of the
orbit
Forms the lower jaw
Mandible
Section 7.6: The Vertebral Column (Spine) has four spinal curves
1. The cervical curve – at the neck (C1 – C7)
2. Thoracic – upper back (T1 – T12)
3. Lumbar – Lower back (L1 – L5)
4. Sacral – sacral bone and coccyx
Vertebrae – provides a column of support for the body, bearing the weight of the head, neck, and trunk, and
ultimately transferring the weight to the appendicular skeleton of the lower limbs; also protects the spinal cord and
helps maintain an upright body position
Sacrum – vertebrae that begin fusing shortly after puberty, and protects the reproductive, digestive, and urinary
organs, and attaches the axial skeleton to the pelvic girdle of the appendicular skeleton
Section 7.7: Five Vertebral regions
1. Cervical – 7 bones
a. The Atlas (C1) holds up the head and articulates with the occipital condyles of the skull; named
after Atlas in Greek mythology who holds the world on his shoulders, allowing the head to make
“yes” movements (nodding).
b. The Axis (C2) is fused to the atlas forming a pivot point called the dens; The “earth” rotates on its
axis, allowing us to make “no” movements (sideways movements).
2. Thoracic – 12 bones – provides bony support to the walls of the thoracic cavity
a. Ribs (AKA Costae) – elongated, curved, flattened bones that originate on or between the thoracic
vertebrae and end in the wall of the thoracic cavity
i. True ribs – vertebrosternal ribs – first seven pairs that are connected to the sternum by
separate cartilage extensions (costal cartilages)
ii. False ribs – vertebrochondral ribs - Ribs # 8-12 do not attach directly to the sternum
iii. Floating ribs – vertebral ribs - #s 11-12 because they have no connection to the sternum,
but attached only to the vertebrae and muscles of the body wall
b. Sternum – breastbone that forms in the anterior midline of the thoracic wall
3. Lumbar – 5 bones
4. Sacral – protects reproductive, digestive, and urinary organs, and attached the axial skeleton to the pelvic
girdle of the appendicular skeleton
5. Coccygeal – provides an attachment site for ligaments and muscles that constricts anal opening
TIP: to remember the number of bones in the first three spinal curves, think about mealtimes. You eat breakfast at
7 am, lunch at 12, and dinner at 5 pm.
Chapter 8 – The Appendicular Skeleton
Appendicular skeleton: includes the bones of the limbs and the supporting elements (girdles) that connect them to
the trunk; standing, walking, writing, turning pages, eating, dressing, shaking hands, waving, etc.; allows you to
manipulate objects and move from place to place
There are four major segments of the appendicular skeleton:
1. Pectoral girdle (4 bones) – shoulder girdle
2. Upper limbs (60 bones)
3. Pelvic girdle (2 bones)
4. Lower limbs (60 bones)
Section 8.1: The pectoral girdle attaches to the upper limbs and consists of the clavicles and scapulae
The pectoral girdle: shoulder girdle that consists of 2 S-shaped clavicles (collarbones) and 2 broad, flat scapulae
(shoulder blades)
Section 8.2: The upper limbs are adapted for freedom of movement
In anatomical descriptions, the term “arm” only refers to the proximal portion of the upper limb (from shoulder to
elbow), not to the entire limb.
Humerus – the bone of the arm, or brachium, which extends from the scapula to the elbow
Ulna – in the anatomical position, the ulna lies medial to the radius of the forearm.
Radius – the lateral bone of the forearm
Carpal bones – wrist that contains 8 bones that form two rows, one with four proximal carpal bones and the other
with four distal carpal bones
Metacarpal bones – 5 bones in the hand that articulate with the distal carpal bones and support the hand
 Distally, the metacarpal bones articulate with the proximal finger bones. Each hand has 14 phalanges
(finger bones). The thumb, or pollex, has two phalanges (proximal and distal), while each of the other
fingers have three phalanges (proximal, middle, and distal).
Section 8.3: The pelvic girdle attaches to the lower limbs and consists of two coxal bones
The pelvic girdle: consists of two coxal (hip) bones; because they must withstand the stresses involved in weight
bearing and locomotion, the bones of the pelvic girdle are more massive than those of the pectoral girdle, and the
bones of the lower limbs are more massive than those of the upper limbs.
The pelvis: consists of the two coxal bones, the sacrum, and the coccyx
The Female pelvis is somewhat different from a male, resulting from adaptations for childbirth, and variations in
body size and muscle mass.
In females:
 The pelvis is generally smoother and lighter and has less prominent markings
 An enlarged pelvic outlet
 A broader pubic angle (the inferior angle between the pubic bones), greater than 100⁰
 Less curvature on the sacrum and coccyx, which in males arcs into the pelvic outlet
 A wider more circular pelvic inlet
 A relatively broad pelvis that does not extend as far superiorly (a “low pelvis”)
 Ilia that project farther laterally, but do not extend as far superior to the sacrum
These adaptations are related to the support of the weight of the developing fetus and uterus, and the passage of
the newborn through the pelvic outlet during delivery.
Section 8.4: The lower limbs are adapted for locomotion and support
Femur: the longest and heaviest bone in the body; articulates with the coxal bone at the hip joint and with the tibia
at the knee joint.
Patella: a large sesamoid bone that forms within the tendon of the quadriceps femoris (a group of muscles that
extend the knee
Tibia: (shinbone) the large medial bone of the leg
Fibula: parallels the lateral border of the tibia
Tarsal bones: (ankle) consists of 7 bones of the ankle
Metatarsal bones: five long bones that form the distal portion of the foot
 The phalanges (toe bones) have the same anatomical organization as the fingers. The toes contain 14
phalanges. The hallux (big toe) has two phalanges (proximal, distal) and the other four toes have three
phalanges each (proximal, middle, distal).
Section 8.5: Sex differences in the human skeleton
Region and Feature
Skull
General appearance
Forehead
Sinuses
Cranium
Mandible
Teeth
Pelvis
General appearance
Pelvic inlet
Iliac fossa
Ilium
Angle inferior to pubic symphysis
Sacrum
Coccyx
Other Skeletal Elements
Bone weight
Bone markings
Male (compared with female)
Female (compared with male)
Heavier, tougher
More sloping
Larger
About 10% larger on average
Larger, more robust
Larger
Lighter, smoother
More vertical
Smaller
About 10% smaller
Smaller, lighter
Smaller
Narrower, more robust, rougher
Heart shaped
Deeper
More vertical; extends farther
superior to sacroiliac joint
Under 90⁰
Long, narrow triangle with
pronounced sacral curvature
Points anteriorly
Broader, lighter, smoother
Oval to round shaped
Shallower
Less vertical; less extension superior
to sacral articulation
100⁰ or more
Broad, short triangle with less
curvature
Points inferiorly
Heavier
More prominent
Lighter
Less prominent