The Muscles (Myology)

By

Dr.Pardeep Kumar

The General Description of Muscles

The Muscular System
Muscles are responsible for all types of body movement they contract or shorten and are the machine of the body.Skeletal is a voluntary muscleSkeletal muscles share 40% of body weight.
Muscular System

Characteristics of Muscles
Muscle cells are elongated (muscle cell = muscle fiber)Contraction of muscles is due to the movement of microfilaments
Muscular System

Skeletal Muscle Characteristics
Most are attached by tendons to bonesCells are multinucleateStriated have visible bandingVoluntary subject to conscious controlCells are surrounded and bundled by connective tissue = great force, but tires easily
Muscular System

Muscular System
Skeletal Muscles (striated or voluntary muscles)

are those which attach to bones and have the main function of contracting to facilitate movement of our skeletons.

Muscular System
Structure of skeletal muscle
Structure of skeletal muscle

Muscular System
Structure of skeletal muscle
Epimysium: This is the connective tissue wrap just under the deep fascia that surrounds the entire muscle Perimysium: This connective tissue surrounds each individual fascicle (bundle of muscle fibers). Endomysium: This is the connective tissue wrapped around each individual muscle cell (fiber). Myofibrils: threadlike fibrils that make up the contractile part of a striated muscle fiber. Fascia on the outside of the epimysium

skeletal muscle structure
Structure of skeletal muscle

Muscular System
Muscle fibers are made up of a group of myofibrils.

Myofibrils contain myofilaments.

The myofibrils have distinct, repeating microanatomical units, termed sarcomeres, which represent the basic contractile units of the muscle fiber/cell (myocyte).

Myofilaments (actin & myosin) are responsible for muscle movement.
Structure of skeletal muscle
Structure of skeletal muscle

Muscular System
Myofilaments: (Thick and Thin)Myosin: thick filamentsActin: thin filamentsA unit of thick and thin filaments is known as a Sarcomere.These structures hold the key to muscle contraction. The staggered thin and thick filaments has the effect as one might pull a rope towards oneself hand over hand.

Structure of skeletal muscle

Muscular System
Structure of skeletal muscle

Muscular System
Structure of skeletal muscle

Skeletal Muscle Attachments
Epimysium blends into a connective tissue attachmentTendon cord-like structureAponeuroses sheet-like structureSites of muscle attachmentBonesCartilagesConnective tissue coverings
Muscular System

Muscular System
Origin and insertion of muscles
Muscles are attached to at least two pointsOrigin: the point where the tendon attaches to the bone which does not move during muscle action.Insertion: the point where the tendon attaches to the bone which moves during an action.e.g. Action of biceps muscle: Scapula is origin (Proximal point) and radius is the insertion. (distal point)

Action of skeletal Muscles
Prime mover muscle with the major responsibility for a certain movementAntagonist muscle that opposes or reverses a prime moverSynergist muscle that aids a prime mover in a movement and helps prevent rotation
Muscular System

Naming of Skeletal Muscles
Direction of muscle fibersExample: rectus (straight)Relative size of the muscleExample: maximus (largest)
Muscular System

Naming of Skeletal Muscles
Location of the muscleExample: many muscles are named for bones (e.g., temporalis)Number of originsExample: triceps (three heads)
Muscular System

Naming of Skeletal Muscles
Location of the muscles origin and insertionExample: sterno (on the sternum)Shape of the muscleExample: deltoid (triangular)Action of the muscleExample: flexor and extensor (flexes or extends a bone)
Muscular System

Muscular System
It includes:-Muscles of BackMuscles of thoraxDiaphragm Muscles of abdomen

The muscles of back
Superficial groupTrapezius Latissimus dorsiLevator scapulaeRhomboideus MajorRhomboideus Minor

TrapeziusOrigin medial 3rd of superior nuchal line of occipital boneExternal occipital protuberanceLigamentum nuchaeSpine of 7th cervicle vertebraeT1 T12 spinesCorresponding supraspinatous ligamentsInsertion Lateral 3rd of clavicleAcromion & upper lip of crest of spineMedial end of spine of ScapulaAction Rotate the scapula during abduction of the arm beyond 90 Weakness of this muscle leads to dropping shoulder

Muscular System
Base of skull(occipital protuberance)

Latissimus DorsiOrigin posterior part of iliac crestSpines of lower 6 Thoracic vertebraelower 3 or 4 ribs Lumbar FasciaInferior angel of scapula Insertionfloor of the inter tubercular sulcusNerve Supply Thoracodorsal nerveAction It extends, adducts & medailly rotates the arm

Levator ScapulaeOriginTransverse process of upper 4 cervical vertebraeInsertionSuperior angle & Medial border of scapulaNerve SupplyDorsal scapular nerve3rd & 4th cervical nerve Action Elevation of scapula

Rhomboideus MajorOrigin 2nd 5th thoracic spineI Medial border of scapulaNerve Supply Dorsal scapular nerveAction Elevates the medial border & of scapula & pulls it medially

Rhomboideus MinorOriginLower part of ligamentum nuchaeSpines of lower 7th cervicle & 1st thoracic vertebraeInsertionMedial border of scapulaNerve Supply Dorsal scapular nerveAction Elevates the medial border of scapula & pulls it medially

Triangle of auscultation
Small triangular gap at the backBoundarySuperiorly - Lateral border of Trapezius Laterally - Medial border of scapula Inferiorly - Upper border of latissimus dorsi. Floor is by seventh rib, 6th & 7th intercostal spaces & rhomboideus major.

Clinical Importance of auscultationOnly part not covered by the muscle. Used to hear the respiratory sounds are better heard with stethoscopeOn the Right side Breadth sound is auscultatedOn the Left side Any kind of Esophageal obstructions can be by auscultation

Muscles of Thorax

The muscles of thorax
Extrinsic musclesPectoralis major Pectoralis minorSerratus anteriorIntrinsic musclesIntercostales externi Intercostales interni

Pectoralis major
OriginAnterior surface of medial half of clavicleAnterior surface of sternum6th costal cartilage

Insertion Crest of great tubercle of HumerusAction Adduction Flexion Medical rotation

Pectoralis minor(lies deep to pectoralis major)
Origin Anterior external surface of 3rd to 5th ribs.Insertion Coracoid process of scapulaAction Forward and downward movement of scapula

Serratus anterior
Origin External surface of upper 8~9 ribs.Oblique externus abdominisInsertion Anterior surface of medical border of scapula

Intercostales externiOrigin: lower border of each ribInsertion: upper border of each rib Action: elevate the rib (muscles of inspiration)Replaced anteriorly by external intercostals membrane.Intercostales interniOrigin: upper border of ribInsertion: lower border of rib Action: depress ribs (muscles of expiration)Replaced posteriorly by internal intercostals membrane.

Diaphragm
Shape and position: dome-shaped between thorax and abdomen, consists of a peripheral muscular part and a central tendonOriginSternal part: xiphoid processCostal part: lower six ribs and costal cartilagesLumbar part: arises by two crura from upper 2~3 lumbar vertebraeInsertion: central tendonWeak areas: triangular spaces without muscular tissue Lumbocostal triangle: between costal and lumbar parts. Sternocostal triangle: between costal and sternal parts.

Openings in the diaphragmAortic hiatuslies anterior to the body of the 12th thoracic vertebra between the crura. It transmits the aorta, thoracic ductEsophageal hiatus for esophagus and vagus nerves at level of T10. Vena cava foramen for inferior vena cava, through central tendon at T8 level
T8
T10
T12

Action:Contraction: the dome moving downward, increases the volume of thoracic cavity which results in inspiration, at the same time the intra-abdominal pressure is increased assists in defecation, vomiting or child birth.Relaxation: the dome returns to the former position, reduces the volume to the thoracic cavity, resulting in expiration.

Muscles of abdomen
Anterolateral groupObliquus externus absominis Oblequus enternus abdominisTransversus abdominisRectus abdominis

Posterior group Quadiatus lumborum Psoas major

Obliquus externus abdominis
Origin : external surface of lower 8 ribs.downward, forward and medially (run down and inward)Insertion : iliac crestThe lower part of aponeurosis of this muscles formsInguinal ligament Lacunar ligament Superficial inguinal ring triangular-shaped defect in aponeurosis of obliquus externus abdominis above pubic tubercle

Obliquus internus abdominis
Deep to obliquus externus abdominisGeneral direction of fibres: upwards, forwards and mediallyOrigin: thoracolumbar fasciaAnterior 2/3rd of iliac crest Lateral 2/3 of inguinal ligamentInsertion:Cartilage of 7th to 10th ribs

Transversels abdominis
Deep to obliquus internus Origin Inner surface of costal cartilage of lower 6 Ribs.Thoracolumbar fasciaIliac crestLateral 1/3rd of inguinal ligamentInsertion Sheath of rectus abdominisInguinal falx with aponeurosis of obliquus internus abdominis

Inguinal falx : arch over spermatic cord, inserted with transverses abdominis fiber into medial part of pecten of pubis Cremaster: around the spermatic cord and testis

Rectus abdominis
Position: lie on to either side of midlineOrigin: pubic crest and symphysisInsertion: xiphoid process and 5th-7th costal cartilagesHas 3-4 tendinous intersections

Similar functions for above four pairs of muscles
Support and compress the abdominal visceraIncrease intra-abdominal pressure, aid in expulsive efforts-vomiting, coughing, sneezing, defecation, urination and childbirth.Depress ribs, assist in (the act of force(4)expiration.Flex, lateral flex, and rotate vertebral column

Sheath of rectus abdominis
Ant layerformed by fusion of aponeurosis of obliquus externus abdominis and anterior leaf of aponeurosis of obliquus internus abdominisPost layerFormed by fusion of posterion leaf of aponeurosis of obliquus internus abdominis and aponeurosis of transverses abdominisAbsent in about 4-5cm below the umbilicus, where aponeuroses of all three muscles form anterior layer the lower free border named arcuate lineBelow this line rectus abdominis in contact with transverse fascia

Linea alba tendinous raphe between right and left recti from xiphoid to pubic symphysis.

Inguinal region
Boundaries Inguinal ligament Lateral margin of rectus abdominisA horizontal line stretching from anterior iliac spine to lateral margin of rectus abdominis

Descent of testes
Seven-week embryo showing the testis before its descent from the dorsal abdominal wall

Fetus at 28 week the testis passing through the inguinal canal

Newborn

Inguinal canal
Position: oblique passage, 4cm long, located 1.5cm above medial half of inguinal lig.

BoundariesAnt wallAponeurosis of obliquus externus abdominisObliquus internus abdominis (lateral third of wall)

Post wallTransverse fascia Inguinal flax mediallyRoofarched lower fibers of obliquus internus and transversua abdominisFlooringuinal lig

Two openingsSuperficial inguinal ring Deep inguinal ring defect in transverse fascia 1.5cm above midpoint of inguinal ligament

Structures passing through the inguinal canal Spermatic cord and ilioinguinal nerve in males Round ligament of uterus and ilioinguinal nerve in females

Inguinal Triangle (of Hesselbach)
Boundaries Inguinal ligament inferiorlyLateral border of rectus abdominis medially Inferior epigastric artery laterally

THANKYOUVERY MUCH

*
*
*
*
*
*
*
*
*
*
*
*