Biology 2401 A&P I - Notes exam 2 - Skeletal System Ch. 7
Functions of skeletal system : support of body
protection of soft organs
production of blood cells
movement (as levers)
storage of minerals and fat
Dynamic system of levers and support elements - active tissues, about 10% blood supply
Each bone is an organ made of tissues - bone, cartilage, loose and dense connective,
nerve tissues.
Some key root terms: osteo- = bone
peri- = around
epi- = on, over
-cyte = cell
-blast = produce, precursor
-clast = break down
- physis = growth
Structure of bones:- most have compact, or dense, bone on outer surface
- with spongy, cancellous, bone inside (honeycomb)
- surfaces covered with periosteum (outer) or endosteum (inner)
periosteum and endosteum are dense connective tissue (fibrous) sheet
that contain nerves, blood vessels and undeveloped bone cells
collagen fibers continuous with collagen fibers in bone matrix and in
tendon or ligament
osteocytes live in small cavities called lacunae; lacunae are connected by small
canals called canaliculi (allow blood vessels to each cell).
7.3
osteocytes produce collagen fibers that attract inorganic salts (calciun phosphate)
to form rigid matrix.
in compact bone osteocytes form concentric rings around blood vessel in central
canal (Haversian canal).
central canal and concentric layers of osteocytes form osteon (Haversian system);
these tend to run longitudinally along bone.
Gives resistance to bending.
Spongy bone does not have osteon arrangement; forms as series of thin plates and
rods at angles to each other, forms open honeycomb structure
This gives light weight, yet good “compacting” strength
Blood vessels in open spaces (bone marrow - also contains blood tissue)
In response to stress bones develop characteristic patterns:
Long bones, subject to “bending” or lateral stress, develop as hollow, thick wall
tubes of compact bone. *Why?
At ends of bones, subject to compacting stress from many directions, bone
develops as spongy bone.
*What is the advantage of spongy bone over solid compact bone?
*Why is the longitudinal arrangement of osteons important?
Bone remodeling
- Osteoclast are cells derived from white blood cells that digest bone
-Undeveloped cells in periosteum and endosteum divide to produce source
of bone cells
- These cells mature into osteoblast, cells actively producing new collagen
fibers, depositing calcium carbonate and calcium phosphate crystals
(matrix is composed of fibers and crystals)
-Osteoblast become osteocytes when they are enclosed in the matrix, less
active cells that help maintain matrix
Osteoclast digest bone, osteoblast produce new bone matrix - bone remodeling
helps in keeping bone strong, healing and adjusting to changing stress
With aging this process slows and bones are weaker and more brittle.
Bone development and growth:
7.3
Ossification (osteogenesis) is process of replace other tissue with bone
Bones formed from other tissues in two ways - intramembranous and
endochondral
intramembranous - form from patches of osteoblast in fibrous tissue, no cartilage
some bones of skull, clavicle, mandible are examples
endochondral - bone tissue replaces cartilage; cartilage forms model
7.3
Ossification begins in center of bone and expands toward each end - this
area is called diaphysis
Ossification later begins at each end of the bone and forms the ends - these
areas are called the distal (far end) and proximal (near end) epiphysis
The remaining cartilage between the diaphysis and the distal epiphysis and
between the diaphysis and the proximal epiphysis are called
the epiphyseal plates
The diaphysis grows toward the ends of the bone, replacing the epiphyseal
plate
Meanwhile the cartilage of the epiphyseal plates grow toward the end of
the bone - the race is on
The bone grows longer and longer, mostly made of strong bone, but with
“growth plates” of cartilage; this allows growth but provides strength
When diaphysis grows faster and destroys all cartilage of epiphyseal plate
(usually because of surge of sex hormones) the long growth stops.
The contact of the diaphysis and the epiphysis recognized as epiphyseal
line
*What is the advantage of this pattern of growth?
The only cartilage remaining after the epiphyseal plates are broken down
is cartilage on the very ends of the bone; this becomes the articular
cartilage that forms a joint.
The skeleton - know all 206 bones in the body and their position
(more on this later)
7.5-.12
Articulations (joints) - classify the types of joints and know the kinds of movements
around these joints
7.13
Joints classified by amount of movement permitted and by the type tissue
that binds them:
synarthrosis (immovable) / fibrous
suture - example flat bones of skull
gomphosis - held by ligament, ex. teeth in socket
amphiarthrosis (slightly movable) / cartilagenous
symphysis - held by fibrocartilage, ex. disc between
vertebrae, anterior connection of pubis
diarthrosis - (freely movable) / synovial
- distinguished by shapes of articulating surfaces and plane
of movement - know example of each:
gliding - flat surfaces, nonaxial
hinge - axial, 1 plane angular
pivot - axial, rotation only
ellipsoidal (condylar) - axial, 2 plane angular
saddle - axial, 2 plane angular
ball-and-socket - axial, rotational and 2 plane
angular
- movements around synovial joints:
gliding
flexion and extension, hyperextension
abduction and adduction
circumduction
rotation
pronation and supination
inversion and eversion
depression and elevation
protraction and retraction
Know structures of a typical synovial joint and their function
articular cartilage
synovial membrane, synovial fluid
joint capsule formed by ligaments
accessory ligaments (in some)
menisci (in some)
bursae (around some joints)
Review a few specific joints:
Fig 7.35, .36
The Skeleton
7.5 - .12
Know the bone names and the relative position of all bones in the body.
I. Axial skeletal system (80 bones) Table 7.1
A. skull (cranium and facial bones)
1. cranium (“box” that contains brain; cranial cavity)
a. frontal (1) - frontal sinuses
b. parietal (2)
c. occipital (1) - foramen magnum, occipital condyles
d. temporal (2) - external auditory canal, mandibular fossa
mastoid process, zygomatic process
e. sphenoid (1) - sella turcica, sphenoid sinuses
f. ethmoid (1) - cribriform plate, ethmoidal sinuses, perpendicular
plate, superior and middle nasal conchae
2. facial bones (support facial muscles, special senses)
a. maxillae (2) - alveolar process (teeth socket), maxillary sinuses,
palatine process (hard palate)
b. palatine (2) - hard palate
c. vomer (1) - nasal septum
d. zygomatic (2) - zygomatic arch
e. nasal (2)
f. lacrimal (2) - nasolacrimal canal
g. inferior nasal conchae (2)
h. mandible (1) - alveolar process (teeth sockets), condylar process,
coronoid process, body, ramus
i. hyoid (1)
j. auditory ossicles (6) - malleus, incus and stapes (pg 271)
Be able to identify the bones that form the orbits, the nasal cavity, the hard palate, the
bones that have sinuses connected to the nasal cavity.
B. neck and trunk
1. vertebral column - know the following structures for each vertebra:
body, transverse process, spinous process, articular facet, vertebral arch,
vertebral foramen, intervertebral foramen, intervertebral disc
Fig. 7.18-.19
-Also, know how each region is distinct)
- intervertebral discs carry weight, articular facets limit twisting
`
a. cervical vertebrae (7, C1 - C7)
- all have transverse process with transverse foramen
- atlas (C1) - lacks body
- axis (C2) - odontoid process (dens)
- vertebra prominens (C7)
b. thoracic vertebrae (12, T1-T12) - articular surface for ribs
c. lumbar vertebrae (5, L1-L5) - heavily built body
d. sacrum (5 fused sacral vertebrae from embryo)
- articulates with pelvic girdle
e. coccyx (3-5 fused coccygeal vertebrae)
Spinal curves - at birth single curve, concave from anterior view
Fig. 7.17
- 4 distinct curves develop to place face forward and to balance body:
cervical curve (convex), thoracic (concave), lumbar (convex), sacral
(concave)
2. thoracic cage
Fig. 7.21
a. ribs - 12 pairs, pair 1 - 7 true ribs - individual costal cartilage
pair 8 -12 false ribs - 8-10 fused costal cartilage
pair 11-12 floating ribs- do not connect to sternum
- costal cartilage connects ribs to sternum
- synovial joints to ribs
b. sternum - 3 parts fuse - manubrium, body and xiphoid process
II. Appendicular skeleton - bones of the arms and legs and the girdles that attach to axis.
A. upper limb
7.10
1. pectoral girdle
a. clavicle (2)
b. scapula (2) - spine, glenoid fossa, coracoid process, acromion
The pectoral girdle is specialized to be very flexible to give arms wide range of motion describe specific features that allows flexibility.
2. arms
a. humerus (2) - head, capitulum, trochlea, olecranon fossa
b. ulna (2) - medial
Pivot joint between radius and ulna allow
c. radius (2) - lateral
pronation and supination
3. wrist and hand
a. carpals (16 , 8/hand) - gliding joints between carpals
b. metacarpals 10, 5/hand) - The proximal metacarpal of the thumb
and the trapezium (one of the carpals) form a saddle joint. This allows the thumb to be
opposable to the fingers, allowing power grip and precision grip. Why is this important?
c. phalanges (1 is phalanx) - (28, 14/hand, 3/finger and 2/thumb)
Muscles that flex and extend fingers located in lower arm, with tendons passing through
the carpal tunnel.* What is the advantage and disadvantage of this arrangement?
*The upper limb is very flexible and adapted to allow manipulation. Describe four
anatomical features that allow this.
B. lower limb - more heavily built, and less flexible, to carry weight. 7.11-.12
1. pelvic girdle - coxae (2), each composed of ischium, ilium and pubis.
- acetabulum, iliac crest, obturator foramen, pubic symphysis
- "pelvis" is sacrum, coccyx and coxal bones
*What is the difference between the “false” and “true” pelvis?
*How does the male pelvis differ from the female pelvis? Fig 7.29
2. leg
a. femur (2) - greater and lesser trochanter, capitate ligament,
medial and lateral epicondyles and condyles
b. patella (2)
c. tibia (2) - medial and lateral condyle, medial malleolus
d. fibula (2) - lateral malleolus
*Tibia is the weight bearing bone in the lower leg, forming the knee and ankle joint.
How does this compare to the “double” bone in the lower arm?
3. ankle and foot
Fig 7.32, 7.33
a. tarsals (14, 7/foot)
- calcaneus attaches to calcaneus (Achilles) tendon
- talus forms joint with tibia
b. metatarsals (10, 5/foot)
c. phalanges (28, 14/foot)
*Describe the arches of the foot (transverse and longitudinal). What is the function of the
arches of the foot?
*The lower limbs are adapted to carry the weight of the body and withstand the stress of
moving. Describe four anatomical features of the lower limbs that allow them to be
strong.