Transcript No. 3

No. 3
1. Introduction of Myology
2. Introduction of Splanchnology
Chapter 3 Myology
Section 1 Introduction



Muscle tissue constitutes almost one-half of the total
body weight. Much of the body’s form is due to the
numerous muscles that attach to the skeleton and
underlie the skin. Other muscles are located within the
walls of hollow organs and blood vessels.
Muscle types:
The body contains three types of muscles-skeletal muscle,
smooth muscle,
cardiac muscle.
Muscles can be further classified as voluntary and
involuntary, on the basis of the type of control exercised
over their activity.


Voluntary muscles: The contractions of
voluntary muscles are normally under the
conscious control of the individual. Voluntary
muscles are controlled by the portion of the
nervous system known as the somatic nervous
system.
Involuntary muscles: The contractions of
involuntary muscles are generally not under the
conscious control of the individual. Rather, they
are governed by the portion of the nervous
system known as the autonomic nervous system,
as well as by hormones and by factors intrinsic to
the muscles themselves.
Skeletal muscles:
The muscles of locomotor apparatus are the
skeletal (or striated) muscles. All of them are
attached by at least one end to some part of the
skeleton.
The skeletal muscle is voluntary muscle because
its contraction is under the voluntary control.
About 40% of the body weight is shared by the
skeletal muscle.
Each skeletal muscle possesses a definite shape,
structure, location and accessory apparatus, and
is supplied by abundant blood vessels, lymphatics
and nerves, so that, it can be regarded as an
organ.


Smooth muscles: Smooth muscle is so named
because its cells lack the striations evident in
skeletal muscle cells. It is also called visceral
muscle because it is found in the walls of hollow
organs and tubes such as the stomach, intestines,
and blood vessels.
Smooth muscle is involuntary muscle, and its
contractions govern the movement of materials
through the organ systems of the body.
Cardiac muscles: Cardiac muscle is a
specialized type of muscle that forms the wall of
the heart. It is involuntary, like smooth muscle,
and stiated, like skeletal muscle.
Ⅰ. The Morphology of Skeletal
Muscle


Muscle fiber: Each muscle is
composed of a collection of muscle
fibers (cells).
The muscle fiber, bundle of muscle
fibers and the muscle are wrapped
by connective tissue.
1. Connective-tissue coverings

Muscle fibers are held together by thin
sheets of fibrous connective-tissue
membranes called fascia. The fascia that
envelops an entire muscle is called the
epimysium. Fascia also penetrates
muscle, separating the muscle fibers into
bundles called the perimysium. We can
say that the perimysium is the connective
tissue that surrounds each bundle of
muscle fibers. The endomysium envelops
the cell membrane of each muscle fiber.
2. Belly and tendon



The fleshy part of a muscle is often called the
belly. At each end of a skeletal muscle the
connective tissue blends with the strong collagen
bundles to form the tendon that anchors it to
the bone, cartilage or articular capsule.
The muscles vary extremely in their shape. It
may be long, short, broad and circular band-like
(sphincter).
Some muscles have more than one belly or one
origin. The fibers of some muscles are oblique to
the long axis of the muscle. Because of their
resemblance to feathers, they are called pinnate
muscles.
Ⅱ. The Origin, Insertion and Action
of Skeletal Muscle
1. Origin and Insertion:
Most of muscles are attached either directly or by
means of their tendons of aponeuroses to bones,
cartilages, ligaments, fasciae or to some
combination of these. Some muscles are attached
to organs, such as the eyeball, and some are
attached to skin or mucous membrane.
When a muscle contracts and becomes short, one
of its attachments usually remains fixed and the
other one moves.
The fixed attachment is called the origin, the
movable one the insertion.
In the limbs, the more distal parts are usually
mobile. Therefore the distal attachment is
usually called the insertion.
However, the terms origin and insertion are
convenient merely for purposes of description.
Sometimes the anatomical insertion remains
fixed and the origin moves.
Sometimes both ends remain fixed, the muscle
then stabilizes a joint.




2. Prime movers (agonists) and antagonist,
synergist and fixators:
During movements of the body, certain principal
muscles are called into action. These muscles,
called prime movers or agonists, contract
actively (shorten and thicken) and produce the
desired movement.
A muscle that opposes the action of a prime
mover is called an antagonist.
The muscles which cooperate in performing an
action are called synergist.
Other muscles, called fixators, steady the
proximal parts of a limb while movements are
occurring in distal parts.
A muscle may act as a prime mover, antagonist,
synergist or fixator under different conditions.
Ⅲ. The Nomenclature of Muscle






The names of muscles usually indicated some
structural or functional feature.
A name may indicate shape, e.g., rhomboid,
trapezius, or gracilis.
A name may refer to location, e.g., tibialis
posterior.
The number of heads of origin is indicated by the
terms biceps, triceps, and quadriceps.
The names of some muscles, such as levator
scapulae and extensor digitorum, depend on their
actions.
Action and shape are combined in the term
pronator quadratus,.
The action and location are combined in the term
flexor digitorum profundus.
Ⅳ. The Supplementary Structures
of Muscles
Ⅰ) The Fascia
 It is formed by connective tissue and
can be divided, from where it is
found, into two groups, superficial
and deep.
1. The superficial fascia
It is found immediately beneath the cutis,
covering almost the entire body.
It is a layer of loose connective tissue containing
fat in varying quantity. The superficial fascia
varies in thickness in different individuals and
different parts of the body. It is very dense in the
scalp, in the palm of hand and the sole of foot. In
the groin it is so thick that is capable of being
subdivided into several laminae. Beneath the
fatty layer of the superficial fascia, there is
generally another layer of the same structure,
comparatively devoid of adipose (fatty) tissue, in
which the trunks of the subcutaneous vessels and
nerves, the superficial lymph nodes, the
mammary gland and certain cutaneous muscles
are found.
2. The deep fascia (proper fascia)


It is a dense, inelastic fibrous membrane, forming
a strong investment, which not only binds down
collectively the muscles in each region, but also
gives a separate sheath to each, as well as to the
vessels and nerves.
In the limbs, the fasciae give off septa which
separate the groups of muscle and attached to
the periosteum. These prolongations of fasciae
are usually called the intermuscular septa. In
certain situations the deep fascia affords
attachment for muscles. It is thickened at the
wrist and ankle to form the retinaculum that
maintains its underlying tendons.
Ⅱ) The Synovial Bursa

It is a connetive tissue sac with a
slippery inner surface, and filled with
synovial fluid. Bursa presents in the
place where tendon rubs against
bone, ligament, or other tendon, or
where skin moves over a body
prominence.
Ⅲ) The Tendinous Sheath


The tendinous sheath is usually
located in the hand and foot in which
the tendon runs. It constitutes
fibrous layer (fibrous sheath of
tendon) and synovial layer
(synovial sheath of tendon).
Synovial sheath of tendon is a
double layered synovial sheath. The
outer layer is parietal layer and the
inner layer is visceral layer. The
mesotendom forms the continuity
between the inner and outer
synovial layers and carries blood
vessels to the tendon. The inner
layer of the synovial sheath is fused
with the tendon. The fluid in the
cavity of the sheath is similar to
synovial fluid of the joint cavity and
facilitates movement by minimizing
friction.
Ⅳ) The Sesamoid Bones

They are developed in those tendons
exert a great amount of pressure
upon the part over which they glide.
They minimize the friction, change
the direction of pulling force and
stengthen the force of the muscle.
PART Ⅱ
SPLANCHNOLOGY
Chapter 1 Introduction


Viscera and Splanchnology:
Viscera are the organs that are mainly situated
in the thoracic, abdominal and pelvic cavities and
fulfill the metabolism and maintain the life of the
species.
They are associated with the pleura and
peritoneum.
According to the functions which they perform,
the viscera can be arranged in the alimentary
system, respiratory system, urinary system
and genital system.
Splanchnology means the study of viscera.




Functions:
The main functions of the viscera are to fulfill the
metabolism and maintain the life of the species.
The alimentary system is adapted to ingest
foods, to secrete enzymes that modify the sizes
of food molecules, to absorb the products of this
digestive action, and to eliminate the unused
residues.
The respiratory system is to carry out the gas
exchanges-supply of oxygen for the living cells
and remove of carbon dioxide resulting from cell
metabolism.
The primary function of the urinary system is to
keep the body in homeostasis by removing and
restoring selected amount of water and solutes.
It also excretes selected amount of various
wastes.
The functions of the genital system are to
produce germ cells and to secrete some
hormones.
Ⅰ. General Structure of Viscera

According to their general structures,
in each of the three chief
subdivisions, the alimentary,
respiratory and the urogenital
system, two principal constituents
may be recognized, i.e., a tubular
canal and a series of non-tubular so
called parenchymatous organs.
Ⅰ) The Tubular Viscus

The basic arrangement of tissue
layers in the wall of tube of viscera is
best seen in the alimentary system.




The wall of the alimentary tract, particularly those
from the esophagus to the anal canal, consists of:
Mucous membrane (mucosa): possessing the
functions of secreting and absorbing.
Submucosa: external to the mucosa, consisting
of areolar tissue.
Muscular coat: outside the submucosa, with two
muscular coats—an outer longitudinal one and an
inner circular one.
Serosa (adventitia): It is the outermost coat of
the tract and is composed of a thin layer of
connective tissue and a mesothelium on those
organs that lie in the abdominal and pelvic
cavities.


The respiratory tract consists mainly
of the mucosa, submucosa and
outermost coat, the latter is
composed of cartilages and
connective tissue.
The wall of the urogenital tract
consists of three layers of tissues—
the mucous coat, the muscular coat,
and the fibrous coat.
Ⅱ) The Parenchymatous Organ


The parenchymatous organ is encased in a
thin, fibrous capsule from which fibrous
partitions pass into the interior to divide
the organ into units known as lobules.
There is a somewhat depression or slit on
the surface of the viscus named the hilum
or porta, such as the hilum of lung, the
porta hepatis and the hilum of kidney,
where the structures which form the root
of the viscus enter and leave the viscus.
Ⅱ. Reference Lines and Abdominal
Regions

In order to observe the relative
locations and the arrangements of
internal organs, it is necessary to
mark reference lines on the surface
of thorax and to subdivide abdomen
into regions.
Ⅰ) The Common Used Reference
Lines of the Thorax
1. The anterior median line
A vertical line through the median of the
sternum.
2. The sternal line
A vertical line through the two sides of the
sternum.
3. The midclavicular line
It extends downward vertically from the
midpoint of the clavicle and usually coincides with
the mammary line in male.
4. The parasternal line:
It extends downward vertically through the
midway between the sternal line and
midclavicular line.
5. The anterior axillary line
A vertical line downward from the anterior
axillary fold.
6. The midaxillary line
A vertical line midway between anterior and
posterior axillary line.
7. The posterior axillary line
A vertical line downward from the posterior
axillary fold.
8. The scapular line
A vertical line through the inferior angle of the
scapula.
9. The posterior median line (vertebral line)
A vertical line through the spines of the thoracic
vertebrae.
Ⅱ) The Abdominal Regions
To make it easier to describe the location
of the organs of the abdomen, the
abdominal cavity is divided into nine
regions by 4 imaginary lines, two
horizontal and two vertical.
 two vertical lines bisect the inguinal
ligaments;
 two horizontal lines: one passes along the
lower edge of the rib cage and another
that runs across the upper edges of the
hip bones (iliac crests).




These regions are:
Umbilical: located centrally, surrounding the
umbilicus (navel).
Lumbar: the regions to the right and left of the
umbilical region.
Epigastric: (epi-means on or above; gastricrefers to the stomach).
The midline region superior to the umbilical
region. As the name implies, most of the stomach
is located in this region.
Hypochondriac: (hypo-means beneath or under;
chondral refers to cartilage)
The regions to the right and left of the epigastric
region.
The name indicates that the hypochondriac
regions are located beneath the cartilage of the
rib cage.


Hypogastric: the midline region directly inferior
to the umbilical region,
Iliac: the regions on either side of the
hypogastric region. The name is derived from the
iliac (hip) bones, which form the lateral
boundaries of the regions. These areas are also
referred to as the inguinal regions .
In practice, it is more common to divide the
abdominopelvic cavity into four quadrants by
means of two intersecting lines; an imaginary
horizontal line and a vertical line that pass
through the umbilicus. These two intersecting
lines (planes) divide the abdominopelvic cavity
into a right upper quadrant; a right lower
quadrant; a left upper quadrant, and a left lower
quadrant.