Cranium – brain case (has 8 bones):
1. Frontal Bone – forehead.
2./3. Parietal Bones – bulging top side of the cranium.
4./5. Temporal Bones – house the middle & inner ear structures.
6. Occipital Bone – creates the framework of the lower back part
of the skull.
7. Sphenoid Bone – resembles bat wings.
8. Ethmoid Bone – forms bony area between the nasal cavity &
the orbits of the eyes.
Face – (has 14 bones):
1./2. Maxillae Bones – upper jaw (upper lip); one on each side.
3. Mandible Bone – lower jaw.
4./5. Zygomatic Bones – cheeks
6./7. Nasal Bones – bridge of the nose; one on each side.
8./9. Lacrimial Bones – helps form tear ducts.
10./11. Inferior Nasal Conchae Bones – ledge protecting the nasal
cavity.
12. Vomer Bone – completes the nasal septum.
13./14. Palatine Bones – hard plate within the mouth.
Appendicular Skeleton – consists of 126 bones.
Classwork (pgs. 204-213) February 25, 1999
?Regions of the Spinal Column?
Hyoid Bone – is below the skill, attached to the bottom of the tongue;
single bone in the neck above the larynx & below the mandible; not
attached to any other bone in the body (sesamoid).
Spinal Column; divided into three types of vertebrae:
Cervical Vertebrae – neck (has 7 bones).
Thoracic Vertebrae – found in the posterior part of the chest or the
thorax (has 12 bones).
Lumbar Vertebrae – found in the small of the back (has 5 bones).
Sacrum – below the vertebral column, a single bone resulted by a fusion
of 5 separate vertebrae.
Atlas – is at the top of the vertebral column, the head sits upon it; has no
body & no spinous processes
Axis – is below the atlas; has a body & a spinous processes.
Coccyx – is below the sacrum, consists of 4 bones fused together (is a tail
bone).
Sternum – is the media part of the anterior chest.
Ribs – 12 pairs or 24; in front (anterior), each of the first 7 ribs joins a
costal cartilage that attach to the sternum. Then the next 3 join the
cartilage of the ribs before, so they are attached to the sternum directly.
The 11th & 12th pairs do not attach & are called floating ribs.
Classwork (pgs. 214-227) February 26, 1999
?Appendicular Skeleton?
Bones of the limbs & their girdles are collectively called the appendicular
skeleton because they are appended to the axial skeleton that forms the
longitudinal axis of the body.
Pectoral (Shoulder) Girdle
Shoulder Girdle – consists of two bones, the anterior clavicle & the
posterior scapula.
Clavicles – collar bones, are slender, doubly curved long bones that can
be felt along their entire courses as they extend horizontally across the
superior thorax.
Scapulae – shoulder blades, are thin, triangular flat bones.
The Upper Arm
Humerus – (arm) articulates proximally with the scapula at the shoulder, &
distally with the radius & ulna at the elbow.
Radius – on the thumb side, has two proximal articulations, the humerus,
& ulna.
Ulna – on the little finger side, articulates proximally with the humerus &
the radius, & distally with cartilage.
7 carpals – wrist.
5 metacarpals- framework of the hand.
14 phalanges – fingers.
Pelvic (Hip) Girdle
Hip Girdle- formed by a pair of coxal bones, which consists of three bones,
which are separate during childhood & fused together during adulthood):
Ilium – the large flaring bone that forms a major portion of a coxal
bone.
Ischium – forms the posteroinferior part of the hip bone.
Pubis – forms the anterior portion of the os coxa.
The Lower Limb
Femur – (thigh bone), is the largest, longest, & strongest bone in the body.
Tibia – the longest & strongest bone in the lower leg; articulates proximally
with the femur, & distally with the fibula & talus.
Fibula – is smaller & more deeply placed, proximally articulates with the
tibia.
7 tarsal – ankles.
5 metatarsals – flat part of the foot.
14 phalanges – toes.
Classwork (pgs. 261-262) March 05, 1999
?General Function of the Muscular System?
There are four general functions of the skeletal system.
Movement – either body as a whole or parts of the body.
Heat Production – muscles produce heat — since there are so many
muscles, they are one of the most important parts of the mechanisms
for maintaining homeostasis.
Posture – continual partial contraction of muscles allow for standing,
sitting, ect.
Stabilizing Joints – muscles help keep everything in place.
There are four characteristics that enable skeletal muscle tissue to
function:
Excitability – the ability to be stimulated, this causes them to be able to
respond to regulatory mechanisms, such as nerve signals.
Contractility – the ability to shorten, which allows muscles to pull on
bones & produces movement.
Extensibility – the ability to stretch & return to the resting length.
Elasticity – the ability of the muscle fiber to resume to its resting length
after being stretched.
Skeletal muscle cells, are composed of bundles of skeletal muscle fibers
that extend the length of the muscle. They are long cells. They have the
same structural parts as other cells, but they have different names:
Sarcoma – cell membrane.
Sarcoplasmic Reticulum – endoplasmic reticulum.
Sarcoplasm – cytoplasm, it contains mitochondria & many nuclei.
Myofibrils, are bundles of long fibers. They are made up of thick & thin
filaments.
Homework (pgs. 263-265) March 05, 1999
?Attachments?
Most muscles span joints & are attached to bones (or other structures) in
at least two places & when a muscle contracts, the movable bone, the
muscle?s insertion, moves toward the immovable are less movable bone,
the muscles origin. In the muscles of the limbs, the origin usually lies
proximal to the insertion.
Muscle attachments, whether origin or insertion, may be direct or indirect.
In direct attachments, the epimysium of the muscle is fused to the
periosteum of a bone or perichondrium of a cartilage. In indirect
attachments, the muscle?s connective tissue wrappings extend beyond the
muscle as a rope-like tendon or a flat, broad aponeurosis. The tendon or
aponeurosis anchors the muscle to the connective tissue covering of a
skeletal element (bone or cartilage) or to the fascia of other muscles. The
temporalis muscle of the head has both direct & indirect (tendinous)
attachments.
Of the two, indirect attachments are much more common in the body
because of their durability & small size. Since tendons are mostly tough
collagenic fibers, they can cross rough bony projections which would tear
apart the more delicate muscle tissues. Because of their relatively small
size, more tendons than fleshy muscles can pass over a joint — thus,
tendons also conserve space.
Myofibrils
When viewed at high magnification, each muscle fiber is seen to contain a
large number of rod-like myofibrils that run in a parallel fashion & extend
the entire length of the cell. Each are 1-2 m in diameter, the myofibrils are
so densely packed that the mitochondria & other organelles appear to be
squeezed between then. There are hundreds to thousands of myofibrils in
a single muscle fiber, depending on its size, & they account for about 80%
of the cellular volume. The myofibrils are the contractile elements of the
skeletal muscle cells.
Striations, Sarcomeres, & Myofilaments
Striations – a repeating series of dark & light bands, are evident along the
length of each myofibril. The dark bands are called A bands because they
are anisotropic; that is, they can polarize visible light. The light bands,
called I bands, are isotropic, or non polarizing. In an intact muscle fiber,
the myofibril bands are nearly perfectly aligned with one another & this
gives the cell as a whole a stripped (striated) appearance.
Each A band has a lighter stripe in the midsection called the H zone
(bright). The H zones are visible only in relaxed muscle fibers. Each H zone
is bisected by a dark line called the M line. The I bands also have a mid-line
interruption, a darker area called the Z discs. A sarcomere is the region of
the myofibril between two successive Z discs. About 2 m long, the
sarcomere is the smallest contractile unit of a muscular fiber. Thus, the
functional units of the skeletal muscle are actually very minute
proportions of the myofibrils, & the myofibrils are chains of sarcomeres
aligned end-to-end like boxcars in a train.
If we examine the banding pattern of a myofibril at the molecular level, we
see that it arises from an orderly arrangement of two types of even
smaller structures, called filaments or myofilaments, within the
sarcomeres. The thick filaments extend the entire length of the A band.
The more lateral thin filaments extend across the I bands & part way into
the A band. The Z discs, also called a Z line, is a coined shaped protein
sheet that anchors the thin filaments & also connects each myofibril to the
next throughout the width of the muscle cell. The H zone of the A band
appears less dense when viewed microscopically because the thin
filaments do not overlap the thick ones in this region. The M line in the
center of the H zone is slightly darker because of the presence of fine
strands that hold adjacent thick filaments together in that area.
A longitudinal view of the mylofilaments is a bit misleading because it gives
the impression that each thick filament interdigitates with only four thin
filaments. In areas where thin & thick filaments overlap, each thick
filament is actually surrounded by a hexagonal arrangement of six thin
filaments.