Introduction to basic human anatomy

1. Introduction to basic human
anatomy
SKIN, FASCIA AND MUSCLES
Dr. Mohammed Mahmoud Mosaed

2. COVERINGS OF THE HUMAN BODY
• The entire body is surrounded by three layers or
envelopes, one inside the other. These coverings
separate the body from the external environment.
• These envelopes include (from outside inward)-the
skin (the integument proper),
• The subcutaneous layer (superficial fascia), and
the deep fascia.

3. Skin
The skin is divided into two parts:
1. Superficial part, the epidermis:
2. Deep part, the dermis .
The epidermis :
• Is a stratified epithelium
• On the palms of the hands and the soles of
the feet, the epidermis is extremely thick.
• In other areas of the body, for example, on
the anterior surface of the arm and forearm,
it is thin.
The dermis:
• Is composed of dense connective tissue
containing many blood vessels, lymphatic
vessels, and nerves.
• Shows considerable variation in thickness in
different parts of the body, tending to be
thinner on the anterior than on the posterior
surface.
• It is thinner in women than in men.
• The dermis of the skin is connected to the
underlying deep fascia or bones by the
superficial fascia, otherwise known as
subcutaneous tissue.

4. The appendages of the skin:
Are the nails, hair follicles, sebaceous glands, and sweat glands.
A. Nails
• Are keratinized plates on the dorsal
surfaces of the tips of the fingers and
toes.
• The proximal edge of the plate is the root of the nail.
• With the exception of the distal edge of the plate, the nail is
surrounded and overlapped by folds of skin known as nail
folds.
• The surface of skin covered by the nail is the nail bed
B Hairs
• Grow out of follicles, which are invaginations of the epidermis
into the dermis. The follicles and their expanded extremities,
called hair bulbs
• Each hair bulb is concave at its end, and the concavity is occupied
by vascular connective tissue called hair papilla.
• A band of smooth muscle, the arrector pili, connects the
undersurface of the follicle to the superficial part of the dermis.
• Hairs are distributed in various numbers over the whole surface
of the body, EXCEPT on the lips, the palms of the hands, the sides
of the fingers, the glans penis and clitoris, the labia minora and
the internal surface of the labia majora, and the soles and sides
of the feet and the sides of the toes.

5. The appendages of the skin:
C. Sebaceous glands
• Pour their secretion, the sebum, onto the
shafts of the hairs as they pass up through the
necks of the follicles. They are situated on the
sloping undersurface of the follicles and lie
within the dermis.
• Sebum is an oily material that helps preserve
the flexibility of the emerging hair. It also oils
the surface epidermis around the mouth of the
follicle.
D. Sweat Glands
• Are distributed over the surface of the body,
EXCEPT on the red margins of the lips, the nail
beds, and the glans penis and clitoris.
• These glands extend through the full thickness
of the dermis, and their extremities may lie in
the superficial fascia.
• The sweat glands are the most deeply
penetrating structures of all the epidermal
appendages.

6. FASCIA
The fasciae of the body can be divided into two
types:
1. Superficial
2. Deep—and lie between the skin and the
underlying muscles and bones
• The superficial fascia, or subcutaneous
tissue, is a mixture of loose areolar and
adipose tissue that unites the dermis of the
skin to the underlying deep fascia
• The deep fascia is a membranous layer of
connective tissue that invests the muscles
and other deep structures .
• Fibrous septa extend from the deep surface
of the membrane, between the groups of
muscles (intermuscular septa), and in many
places divide the interior of the limbs into
compartments
• In the region of joints, the deep fascia may be
considerably thickened to form restraining
bands called retinacula .
• Their function is to hold underlying tendons
in position or to serve as pulleys around
which the tendons may move.

7. Muscle tissues
• definition of muscular tissue: tissue composed
of bundles of elongated cells capable of
contraction and relaxation to produce movement.
• There are three types of muscle tissue
• a. Skeletal muscle
• b. Smooth muscle
• c. Cardiac muscle

9. Skeletal Muscle
The skeletal muscle characterized by:
• 1. Attached to the skeleton; each muscle attached to two or
more bones
• 2. produce the movements of the skeleton
• 3. They are called voluntary muscles
• 4. They are made up of striped muscle fibers

10. origin
Insertion
• The origin of a muscle is where
the muscle starts ("the starting
point").
• The insertion of a muscle is
where the muscle ends ("the
ending point").
Also the attachment that moves the
least is referred to as the origin, and
the one that moves the most, the
insertion

11. General Construction of a Skeletal Muscle
• The muscle consists of fleshy part and
fibrous part
• The fleshy part is the belly of muscle
• The fleshy portion may be directly
connected to the bone.
• The fibrous part may be:
• Tendon
• Aponeurosis
• Raphe

12. Skeletal Muscle
• The muscles attached to the bones by:
• Tendon is cord-like band of tough, inelastic
fibrous tissue
• Aponeurose thin broad but strong sheet of
fibrous tissue.
• A raphe is an interdigitation of the tendinous
ends of fibers of flat muscles.

14. Internal Structure of Skeletal Muscle
• The muscle fibers are bound together
with delicate areolar tissue, which is
condensed on the surface to form a
fibrous envelope, the epimysium.
• The individual fibers of a muscle are
arranged either parallel or oblique to
the long axis of the muscle.
• Examples of muscles with parallel fiber
arrangements are the
sternocleidomastoid, the rectus
abdominis, and the sartorius.

15. Shapes of skeletal muscles:
• The skeletal muscles classified
according to the direction of
fibers into
• 1. Parallel muscles whose
fibers run parallel to the
longitudinal axis of muscle
(axis of pull)
Example; the
sternocleidomastoid.

16. • 2. Pennate muscles
Muscles whose fibers run obliquely to the line of pull
Classification of pennate muscles
• A) A unipennate muscle the tendon lies along one side of
the muscle and the muscle fibers pass obliquely to it (e.g.,
extensor digitorum longus).
• B) A bipennate muscle the tendon lies in the center of the
muscle and the muscle fibers pass to it from two sides (e.g.,
rectus femoris).
• C) A multipennate muscle arranged as a series of
bipennate muscles lying alongside one another (e.g., the
deltoid) or may have the tendon lying within its center and
the muscle fibers passing to it from all sides, converging as
they go (e.g., tibialis anterior).

18. 3. Convergent muscles: the muscle fibers converge
on the insertion to maximize the force of muscle
contraction. Examples: Pectoralis Major muscle.
4. Circular muscles: the muscle fibers surrounded
opening to act as a sphincter. Examples: Orbicularis
oris and Orbicularis oculi muscles.
5. fusiform muscles: some texts classify parallel
muscles that are slightly wider in their middle
(spindle shaped) as fusiform.

20. Ways of working of muscle
A muscle may work in the following four ways:
1. Prime mover (Agonist): A muscle is a prime mover when it is the chief muscle or
member of a chief group of muscles responsible for a particular movement.
2. Antagonist: Any muscle that opposes the action of the prime mover is an
antagonist.
3. Fixator: A fixator contracts isometrically (i.e., contraction increases the tone but
does not in itself produce movement) to stabilize the origin of the prime mover
so that it can act efficiently.
4. Synergist: In many locations in the body, the prime mover muscle crosses several
joints before it reaches the joint at which its main action takes place. To prevent
unwanted movements in an intermediate joint, groups of muscles called
synergists contract and stabilize the intermediate joints.
• Many muscles can act as a prime mover, an antagonist, a fixator, or a synergist,
depending on the movement to be accomplished.
• Muscles can even contract paradoxically, for example, when the biceps brachii, a
flexor of the elbow joint, contracts and controls the rate of extension of the elbow
when the triceps brachii contracts.

21. Nerve Supply of Skeletal Muscle
• The nerve trunk to a muscle is a mixed nerve, about
60% is motor and 40% is sensory, and it also
contains some sympathetic autonomic fibers.
• The nerve enters the muscle at about the midpoint
on its deep surface, often near the margin; the
place of entrance is known as the motor point.
• This arrangement allows the muscle to move with
minimum interference with the nerve trunk.

22. Nerve Supply of Skeletal Muscle
• The skeletal muscle
supplied by somatic
nerves
• The motor point is that
specific location on the
surface of the muscle
where the nerve enters.
• A motor unit is the single
motor neuron and the
number of striated
muscle fibers activated
by it (innervation). The
importance of the motor
unit is that its fibers work
in union.

24. Naming of Skeletal Muscles
• Individual muscles are named according to their
shape, size, number of heads or bellies, position,
depth, attachments, or actions
• Shape e.g. deltoid (triangle)
• Size e.g. pectoralis major
• Number of heads e.g. biceps brachii (2 head)
• Position e.g. pectoralis
• Depth internal oblique
• Attachments e.g. sternocleidomastoid
• Action e.g. extensor

26. Smooth Muscle
1. Involuntary non striated muscles
2. Their cells are spindle in shape
3. It present in the tubes of the body
• In the digestive system. A wave of contraction of the circularly arranged
fibers passes along the tube, milking the contents onward. By their contraction, the
longitudinal fibers pull the wall of the tube proximally over the contents. This method of
propulsion is referred to as peristalsis.
• In storage organs such as the urinary bladder and the
uterus.
• In the walls of the blood vessels
• Depending on the organ, smooth muscle fibers may be made to contract by local
stretching of the fibers, by nerve impulses from autonomic nerves, or by hormonal
stimulation.

27. Cardiac Muscle
• Cardiac muscle consists
of striated branched
muscle fibers
• It forms the
myocardium of the
heart.
• Specialized cardiac
muscle fibers form the
conducting system of
the heart.
• Cardiac muscle is
supplied by autonomic
nerve fibers