Movement Unit
Skeletal System: Anatomy
Chapter 6
Components
• Includes all of the bones (206 in adults).
• Includes the cartilage and ligaments that
occur at the joints (Articulations System).
Functions
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•
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Support of the entire body’s weight.
Protection of the viscera.
Production of blood cells (Hemopoesis)
Storage of minerals and fat
Allows for flexible body movement
Types of Bones
• Long: longer than wide (femur)
• Short: cube shaped L=W (talus- foot)
• Flat: platelike and have broad surfaces
(parietal- skull)
• Irregular: varied shapes with many places
for connections (vertebra)
• Round: circular (patella- knee)
Long bone Anatomy
• Periosteum – continuous with ligaments
and tendons. Area where blood vessels
enter the bone. Fibrous connective tissue.
• Epiphysis – expanded portions at each
end. Contains cancellous bone wrapped
in a thin layer of compact bone covered by
hyaline cartilage (articular cartilage).
• Diaphysis – “shaft” of the bone – not solid
contains the medullary cavity with yellow
marrow. Compact bone wraps this cavity.
What are Focal Features?
Review of Histology:
• Compact Bone: Osteons, osteocytes,
Lacunae, Lamellae, hydroxyapatite
([Ca(OH2)]+Ca3(PO4)2 crystals), central
or Haversian canal, canaliculi.
• Spongy Bone or Cancellous bone:
trabeculae, red bone marrow.
• New term- Ossification- process of bone
formation
The Skeletal System
Articulations
Classification
• Classified based on the type of movement they allow.
• 3 major types:
Fibrous Joint – immovable and connected by
fibrous connective tissue (ex: plates in skull,
periodontal ligaments)
Cartilaginous Joint – slight movement and
fibrocartilage is between the 2 bones (ex: betw. spinal
vertebrae & pubic bones)
Synovial Joint – free motion no direct contact of
bones associated with synovial membranes (Ex:
elbow, ankle, shoulder)
Fibrous Joints: minimal
movement
• Sutures: seams between bones, found
between skull bones, form fontanels in
children (e.g. coronal)
• Syndesmoses: bones farther apart than in
a suture and are joined by ligaments (e.g.
radioulnar)
• Gomphoses: specialized joints consisting
of pegs that fit in sockets (e.g.
dentoaveolar)
Cartilaginous Joints: Growth
• Synchondroses: 2 bones joined by
hyaline cartilage (e.g. epiphyseal platescartilaginous region betw. epiphysis &
diaphysis of a growing bone)
• Symphyses: fibrocartilage uniting 2
bones (e.g. symphyses pubis,
manubriosternal (ribcage))
Synovial Joints: Movable
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Plane or gliding: 2 opposed flat surfaces, movement
confined to one plane (e.g. intervertebral)
Saddle: 2 saddle-shaped articulating surfaces
oriented at right angles (e.g. carpometacarpelwrist/hand)
Hinge: convex cylinder in one bone applied to a
corresponding concave portion on another bone
(e.g. elbow and knee)
Pivot: rotation around a single axis. A process that
rotates within a ring (e.g. atlantoaxial-neck)
Synovial Joints
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•
Ball and Socket: ball (head) at the end of
one bone and a socket on another bone
(e.g. coxal-hip and glenohumeralshoulder)
Ellipsoid: modified ball-and-socket the
head is more ellipsoid in shape rather
than round (e.g. atlanooccipitalbetw.head & neck i.e. allows nodding)
Types Movements
• Flexion (anterior or ventral direction) and extension (posterior
or dorsal direction)
• Dorsiflexion (flex toes) and plantar flexion (point toes)
• Abduction (away from midline) and adduction (toward midline)
• Medial and lateral rotation (turning around long axis)
• Circumduction (combination of flexion, extension, abduction,
and adduction)
• Elevation (superior motion) and depression (inferior motion)
• Protraction (moving in anterior direction) and retraction
(moving in posterior direction)
• Supination (face up palm) and pronation (face down palm)
• Opposition (thumb to finger) and reposition
• Lateral excursion (bottom jaw lateral)
• Inversion (ankle medial turn) and eversion (ankle lateral turn)
Muscular System
Chapter 7
Movement Unit
Review:
Fig. 7.1
Functions of Skeletal Muscle:
• Support the body (opposes the force of
gravity)
• Make bones and other body parts move
• Maintain a constant body temperature
• Assist movement in cardiovascular and
lymphatic vessels
• Protect internal organs and stabilize joints
Microscopic Anatomy of Skeletal
Muscle:
• What do we already know from histology?
Striations.
• Arrangement of myofilaments in a muscle
fiber (cell).
• Normal cell with some specialized terms
for cell parts. (Plasma membrane = sarcolema, endoplasmic reticulum =
sarcoplasmic reticulum)
Microscopic Anatomy of Muscle
(Sarcoplasmic Reticulum)
• Remember this is the ER for muscle cells.
• Sarcoplasmic reticulum has specialized
pockets to store calcium ions (Ca2+) which
is essential for muscle contraction.
• The sarcoplasmic reticulum encases
hundreds of myofibrils which allow for
contraction of the muscle cell.
Microscopic Anatomy of Muscle:
• Myofibrils run the length of the muscle
fiber.
• Striations are formed by the placement of
these myofibrils forming sarcomeres.
• Sarcomeres contain two types of protein
fibers: actin (thin and intertwined) and
myosin (thick and shaped like golf club).
Muscles Move
Skeletal Parts
• Skeletal Muscle
– Each muscle fiber is a single
cell with many nuclei
– Each fiber is composed of a
bundle of myofibrils which
contain myofilaments
• Thin filaments—2 strands of actin
• Thick filaments—staggered
arrays of myosin
– Striated appearance due to
sarcomeres (basic functional
unit)
Muscle Contractions:
Sliding-Filament
Model
• Thin and thick filaments
of the sarcomere slide
past one another to
shorten the length of the
muscle
Muscle Contractions
• Motor Unit: A single nerve ending and all
the muscle fibers attached to it
• With a nerve impulse- muscle fibers
contract completely. “all or none”- the
amt. of fibers contracting can vary!
• Does a muscle have to contract
completely?
• Partial contraction of a muscle comes from only
contracting a portion of the fibers (see above)
• Calcium is the so called "trigger" for muscle
contraction. Calcium aids in the formation of
action potential in the motor end plate, and is
later released from the terminal cisternae of the
sarcoplasmic reticulum into the cytosol of a
striated (cardiac and skeletal) muscle cells. Next
the calcium ions bind to troponin which causes a
change in the conformation of the troponintropomyosin complex that exposes the myosin
binding sites on the actin filament. The myosin
heads then attach to the actin filament and a
muscle contraction occurs.
• Chemical energy in muscle fibers is in the
form of ATP. In order to produce physical
energy, ATP is hydrolyzed to become ADP
and Pi (adenosine diphosphate and
inorganic phosphate). When ATP is
broken down into ADP and Pi the cross
bridges are energized which allows for the
"power stroke", or force production of a
muscle contraction.
Source:
http://www.cartage.org.lb/en/themes/sciences/zoology/animalphysiology/muscles/mu
scles.htm
Microscopic Anatomy of Muscle:
• Sliding Filaments – when the muscles are
triggered by motor nerve cells, impulses travel
down the T-tubule of the sarcomere (see
following picture).
Calcium is then released from the sarcoplasmic
reticulum. This causes the sarcomere to
shorten. The actin slides across the myosin.
ATP provides the power for this contraction.
Fig. 7.3a
Fig. 7.5
Connective coverings
• Muscles are covered with fascia (dense
regular connective) which separates
muscles. Deep fascia separates muscles
from each other, superficial fascia-from
skin.
• Fascia are continuous with tendons which
are continuous with the bone periosteum.
Smaller picture
• Muscles are grouped in to fascicles that
are covered with a sheath of connective
tissue called perimysium.
• Fascicles are divided into muscle fibers,
each surrounded by the endomysium
• Blood and nerves reach the muscle
through the endomysium
Exercise
• Atrophy- from lack of use, muscle fibers
are replaced with adipose and fibrous
tissue
– Can cause muscle fibers to shorten enough to
force the body to contort.
• Hypertrophy-more myofibrils develop with
more use
Going the Distance, or not?
• Slow twitch- less fibers per motor unit- better for
endurance sports
– Largely aerobic-extra mitochondria, extra capillaries
– Presence of Myoglobin
• A dark, red oxygen carrying pigment
• Fast Twitch- more fibers per motor unit- better
for powerful, short muscle bursts
– Few mitochondria
– Largley anerobic
– Easily hits maximum tension
Macroscopic Anatomy of Muscle:
• 3 Layers of connective tissue are part of each
muscle:
Epimysium – surrounds entire muscle, dense
layer of collagen fibers.
Perimysium – divides muscle into
compartments called fascicles.
Endomysium – delicate connective tissue that
surrounds each muscle cell or fiber.
• Where these connective tissues run together at
the end of muscles they form tendons or
aponeurosis.
Fig. 7.2a
Fig. 7.9
Fig. 7.10
Fig. 7.10a
Fig. 7.10b
Fig. 7.11
Fig. 7.12
Table 7.1