1. GROSS ANATOMY
SKELETAL MUSCLES
BY TAHIR AMIN SULEHRIA
GRADUATE
STUDENT(FIRST YEAR
2014)

2. MYOLOGY
STUDY OF MUSCLES
THE TERM “MUSCLE” IS DERIVED FROM LATIN WORD “MUSCULUS”
DIMINUTIVE OF “MUS” MEANING MOUSE. THEY WERE NAMED SO
BECAUSE THEIR BELLY RESEMBLES BODY OF THE MOUSE AND
THEIR TENDONS RESEMBLE MOUSE‟S TAIL. MUSCLES ARE
CONTRACTILE TISSUES THAT BRING ABOUT MOVEMENTS OF
DIFFERENT BODY PARTS. THEY CAN BE REGARDED AS MOTORS OF
HUMAN BODY BECAUSE THEY PROVIDE ALL THE FORCE NECESSARY
TO PERFORM DIFFERENT TYPES OF MOVEMENTS. WHETHER IT IS
THE LOCOMOTION OF BODY AS A WHOLE OR JUST MOTION OF ITS
PARTS, ITS ALL BECAUSE OF MUSCLES.

3. TYPES OF MUSCLES
MUSCLES ARE OF THREE TYPES; SKELETAL, SMOOTH AND CARDIAC.

4. SKELETAL MUSCLES
•THEY ARE ALSO KNOWN AS STRIPED, STRIATED, SOMATIC AND
VOLUNTARY MUSCLES
•THEY ARE THE MOST ABUNDANT TYPE AND ARE FOUND ATTACHED TO
THE SKELETON. FOR THIS REASON THEY ARE CALLED SKELETAL
MUSCLES.
•THEY ARE INNERVATED BY SOMATIC NERVOUS SYSTEM AND ARE
THEREFORE UNDER VOLUNTARY CONTROL. THEY OBEY THE WILL OF
HUMAN BEINGS.
•THEY RESPOND QUICKLY TO STIMULI AND ARE CAPABLE OF RAPID
CONTRACTIONS. THEY GET FATIGUED EASILY BECAUSE OF THEIR

5. PARTS OF A TYPICAL
SKELETAL MUSCLE
ENDS:
A TYPICAL SKELETAL MUSCLE CONSISTS OF TWO ENDS.
THESE ARE;
1.ORIGIN IS ONE END OF THE MUSCLE WHICH REMAINS
FIXED DURING ITS CONTRACTION.
2.INSERTION IS THE OTHER END WHICH MOVES DURING ITS
CONTRACTION. IN THE LIMB MUSCLES, THE ORIGIN IS
USUALLY PROXIMAL TO INSERTION.
PARTS:
A TYPICAL SKELETAL MUSCLE CONSISTS OF TWO PARTS.
THESE ARE;
1.FLESHY PART IS CONTRACTILE, AND IS CALLED THE
„BELLY‟.
2.FIBROUS PART IS NON-CONTRACTILE AND INELASTIC.
WHEN CORD-LIKE OR ROPE-LIKE, IT IS CALLED TENDON;
WHEN FLATTENED, IT IS CALLED APONEUROSIS.

6. FASCICULAR
ARCHITECTURE OF
MUSCLES
THE ARRANGEMENT OF MUSCLE FIBERS VARIES ACCORDING TO THE
DIRECTION, FORCE AND RANGE OF HABITUAL MOVEMENT AT A
PARTICULAR JOINT. THE FORCE OF MOVEMENT IS DIRECTLY
PROPORTIONAL TO THE NUMBER AND SIZE OF MUSCLE FIBERS, AND
THE RANGE OF MOVEMENT IS PROPORTIONAL TO THE LENGTH OF
FIBERS. THE MUSCLES CAN BE CLASSIFIED ACCORDING TO THE
ARRANGEMENT OF THEIR FASCICULI INTO THE FOLLOWING
GROUPS.

7. FASCICULAR ARCHITECTURE
OF MUSCLES

8. MUSCLE WITH PARALLEL
FASCICULI
THESE ARE MUSCLES IN WHICH THE FASCICULI ARE PARALLEL TO THE
LINE OF PULL. THESE MUSCLES MAY BE:
1.QUADRILATERAL, FOR EXAMPLE THYROHYOID,
2.STRAP-LIKE, FOR EXAMPLE STERNOHYOID AND SARTORIUS.
3.STRAP-LIKE WITH TENDINOUS INTERSECTIONS, FOR EXAMPLE
RECTUS ABDOMINIS.
4.FUSIFORM, FOR EXAMPLE BICEPS BRACHII, DIGASTRIC.
THE RANGE OF MOVEMENT IN SUCH MUSCLES IS MAXIMUM.

9. MUSCLES WITH OBLIQUE
FASCICULI OBLIQUE TO THE LINE OF PULL, THE
WHEN THE FASCICULI ARC
MUSCLE MAY BE TRIANGULAR, OR PENNATE (FEATHCR-LIKE) IN THE
CONSTRUCTION. THIS ARRANGEMENT MAKES THE MUSCLE MORE
POWERFUL, ALTHOUGH THE RANGE OF MOVEMENT IS REDUCED.
OBLIQUE ARRANGEMENTS ARE OF THE FOLLOWING TYPES:
1.TRIANGULAR, E.G. TEMPORALIS, ADDUCTOR LONGUS.
2.UNIPENNATE, E.G. FLEXOR POLLICIS LONGUS, EXTENSOR DIGITORUM
LONGUS, PCRONCUS TCRTIUS, PALMAR INTCROSSCI.
3.BIPENNATE, E.G. RECTUS FEMORIS, DORSAL INTEROSSEI,
PCRONCUS LONGUS, FLEXOR HALLUCIS LONGUS.
4.MULTIPENNATE, E.G. SUBSCAPULARIS, DELTOID (ACROMIAL FIBERS].
5.CIRCUMPENNATE, E.G. TIBIALIS ANTERIOR.

10. MUSCLES WITH SPIRAL OR TWISTED
FASCICULI
SPIRAL OR TWISTED FIBERS ARE FOUND IN TRAPEZIUS, PECTORALIS
MAJOR, LATISSIMUS DORSI, SUPINATOR, ETC. IN CERTAIN MUSCLES
THE FASCICULI ARE CROSSED. THESE ARE CALLED CRUCIATE
MUSCLES, E.G. STERNOCLEIDOMASTOID, MASSETER AND
ADDUCTOR MAGNUS.

11. NOMENCLATURE OF
MUSCLES
1.ACCORDING TO THEIR SHAPE, E.G. TRAPEZIUS, RHOMBOIDEUS, SERRATUS
ANTERIOR, LATISSIMUS DORSI, ETC.
2.ACCORDING TO THE NUMBER OF HEADS OF ORIGIN, E.G. BICEPS, TRICEPS,
QUADRICEPS, DIGASTRIC, ETC.
3.ACCORDING TO THEIR GROSS STRUCTURE, E.G. SEMITENDINOSUS,
SEMIMEMBRANOSUS, ETC.
4.ACCORDING TO THEIR LOCATION, E.G. TEMPORALIS, SUPRA-SPINATUS,
INTERCOSTALES.
5.ACCORDING TO THEIR ATTACHMENTS, E.G. STYLOHYOID, CRICOTHYROID, ETC.
6.ACCORDING TO THEIR ACTION, E.G. ADDUCTOR LONGUS, FLEXOR CARPI
ULNARIS, ABDUCTOR POLLICIS LONGUS, ETC.
7.ACCORDING TO DIRECTION OF THEIR FIBERS, E.G. RECTUS ABDOMINIS,
TRANSVERSUS ABDOMINIS, ORBICULARIS OCULI.
8.A MUSCLE WITH TWO BELLIES WITH AN INTERVENING TENDON IS CALLED
DIGASTRIC MUSCLE. MUSCLE WITH NUMBER OF INTERVENING TENDONS OR
INTERSECTIONS IS THE RECTUS ABDOMINIS.
9.THE MUSCLES THAT EXTEND OVER TWO OR MORE JOINTS ARE CALLED
DIARTHRIC OR POLYARTHRIC MUSCLES, E.G. FLEXOR CARPI RADIALIS AND
FLEXOR DIGITORUM PROFUNDUS.