Anatomy LC4b Muscular System Trunk PDF

UNIVERSITY OF NORTHERN PHILIPPINES ANATOMY LC4b MUSCULAR SYSTEM: Trunk COLLEGE O...

UNIVERSITY OF NORTHERN PHILIPPINES ANATOMY LC4b MUSCULAR SYSTEM: Trunk COLLEGE OF MEDICINE, BATCH 2026 Transcribers: Achacoso, Acosta, Ammiyao, Anulacion, Avecilla, Busaing Dr. Ana Patricia de Grano | October 2022 Editors: Baltazar, Cabillo, Sadiasa COURSE OUTLINE I. MUSCLES OF THE BACK A. Superficial B. Intermediate C. Deep (Intermediate) D. Thoracolumbar Fascia II. SPINOTRANSVERSALES MUSCLES A. Erector Spinae B. Transversospinales C. Segmental Muscles III. SUBOCCIPITAL MUSCLES IV. STRAIN, SPRAIN, SPASM A. Back Pain B. Back Strain C. Spasm V. MUSCLES OF THE THORAX A. Pectoral Region B. Thoracic Wall VI. MUSCLES OF THE ABDOMEN A. Diaphragm B. Functions and Actions C. Rectus Sheath, Linea Alba, and Umbilical Ring D. Posterior Abdominal Wall VII. PELVIS Figure 1. Muscles of the Back VIII. PERINEUM A. Deep B. Superficial Perineal Pouch Muscle Origin Insertion Innervation Function C. Injury to the Pelvic Floor Trapezius Superior Lateral one MOTOR- Assists in nuchal line, third of accessory rotating the External clavicle, nerve (XI) scapula I. MUSCLES OF THE BACK occipital during Acromion, PROPIOCEPTI Muscles of the back are organized into superficial, intermediate, and protuberance Spine of ON – C3 and abduction deep groups , Scapula C4 of humerus - Extrinsic Muscles – originates embryologically from locations other Ligamentum above than the back (e.g. Superficial and Intermediate groups) horizontal; nuchae, A. Superficial groups Spinous Upper Innervation: Anterior rami of spinal nerves process of C7 fibers Function: Related more on movements of the appendicular group to T12 elevate, particularly the upper limb Middle fibers Superficial Extrinsic Anterior Rami of Related to upper adduct, and Spinal Nerves limb movements Lower (appendicular fibers groups) depress Intermediate Extrinsic Anterior Rami of Respiratory scapula Spinal Nerves Function Latissimus Spinous Floor of Thoracodorsa Extends, Deep Intrinsic Posterior Rami of Directly related to dorsi processes of intertubercul l nerve (C6- adducts and Spinal Nerves head and T7 to L5 and ar sulcus of C8) medially vertebral column sacrum, iliac humerus rotates Table 1. Muscles of the Back: Superficial, Intermediate, Deep crest, ribs 10 humerus to 12 Levator Transverse Upper C3-C4 and Elevates scapulae process from portion dorsal scapula C1 to C4 medial scapular border of nerve (C4,C5) scapula Page 1 of 14  UNIVERSITY OF NORTHERN PHILIPPINES ANATOMY LC4b MUSCULAR SYSTEM: Trunk COLLEGE OF MEDICINE, BATCH 2026 Transcribers: Achacoso, Acosta, Ammiyao, Anulacion, Avecilla, Busaing Dr. Ana Patricia de Grano | October 2022 Editors: Baltazar, Cabillo, Sadiasa Rhomboid Spinous Medial Dorsal Retracts major process from border of scapular (adducts), T2 to T5 scapula nerve (C4, and between C5) elevates spine and scapula inferior angle Rhomboid Lower Medial Dorsal Retracts minor portion of border of Scapular (adducts) ligamentum scapula at nerve (C4, and nuchae, spine of C5) elevates spinous scapula scapula process of C7 to T1 Table 2. Superficial group of Back Muscle B. Intermediate Group A.k.a. Respiratory Group of Muscles Figure 2. Thoracolumbar fascia and the deep back muscles (transverse section) Extrinsic Innervation: Anterior rami of spinal nerves D. Thoracolumbar fascia Function: provides respiratory function because it is the one attached to your ribs. Covers the deep muscles of the back and the trunk Muscle Origin Insertion Innervation Function Critical to the overall organization and integrity of the deep group of back muscles Serratus Lower portion Upper border Anterior rami Elevates posterior of ligamentum of ribs II to V of upper ribs 2 to 5 Superiorly will pass anterior to the Serratus posterior and it is superior continuous with the deep fascia in the neck nuchae, just lateral to thoracic nerve spinous their angles (T2 to T5) In the Thoracic Region, it covers the deep muscles and separates them processes of from the muscles in superficial and intermediate groups. C7 to T2 and Medially, it will attach to the spinous process of the thoracic vertebrae supraspinous and ligament Laterally, to the angles of the ribs Serratus Spinous Lower border Anterior rami Depresses posterior processes of of ribs 9 to 12 of lower ribs 9 to II. SPINOTRANSVERSALES MUSCLES inferior T11 to L3 and just lateral to thoracic 12 and - Together, they draw the head backward, extending the neck. Individually, supraspinous their angles nerves (T9 to may each muscle rotates the head to one side-the same side as the contracting ligaments T12) prevent muscle. lower ribs Your 2 spinotransversales muscles actually bond from your spinous from processes and ligament from nuchae upward and laterally. being Your splenius capitis is a broad muscle which is attached to your elevated occipital bone and mastoid process of your temporal bone while when the splenius cervicis is your narrow muscle which is attached to the diaphragm transverse process of the upper cervical vertebrae. contracts Table 3. Intermediate group of Back Muscles Muscle Origin Insertion Innervation Function Serratus posterior most well-developed group of muscles in swimmers Splenius Lower half of Mastoid Posterior Together Serratus anterior more infinitely related to Latissimus dorsi capitis ligamentum process, rami of draw nuchae, spinous skull below middle head C. Deep (Intrinsic) Group of Back Muscles processes of C7 lateral one cervical backward Intrinsic to T4 third of nerves extending Innervation: Posterior rami of Spinal Nerves superior neck; Function: Directly related to Head, Neck and Vertebral Column nuchal line Individual movements ly – draw The deep or intrinsic muscles of the back extend from the pelvis to the and skull. They include: rotate Splenius capitis and cervicis (spinotransversales muscles)- the head to extensors and rotators of the head and neck one side Erector spinae and transversospinalis- the extensors and rotators (turn face of the vertebral column to same Interspinales and intertransversarii- the short segmental side) muscles Page 2 of 14  UNIVERSITY OF NORTHERN PHILIPPINES ANATOMY LC4b MUSCULAR SYSTEM: Trunk COLLEGE OF MEDICINE, BATCH 2026 Transcribers: Achacoso, Acosta, Ammiyao, Anulacion, Avecilla, Busaing Dr. Ana Patricia de Grano | October 2022 Editors: Baltazar, Cabillo, Sadiasa Splenius Spinous Transverse Posterior Together – cervicis processes of T3 processes rami of extend to T6 of C1 to C3 middle neck; cervical Individuall nerves y – draw and rotate head to one side (turn face to same side) Table 4. Spinotransversales Muscles A. Erector Spinae Muscles Largest group of intrinsic back muscles Lie posterolaterally to the vertebral column between the spinous processes medially and the angles of the ribs laterally. Your erector spinae muscles from your lateral to medial, the most lateral would be your iliocostalis muscles followed by your longissimus muscles and most medial would be spinalis muscles (MNEMONIC: I Like Standing) Helps stabilize back or vertebral column Muscle Origin Insertion Iliocostalis Sacrum, spinous processes Angles of the lower 6 lumborum of lumbar and lower two or 7 ribs thoracic vertebrae and their supraspinous ligaments, and the iliac crest Iliocostalis thoracis Angles of the lower six ribs Angles of the upper six ribs and the transverse process of C7 Iliocostalis cervicis Angles of ribs 3 to 6 Transverse processes of C4 to C6 Figure 3. Deep group of back muscles – transversospinales and segmental muscles Longissimus thoracis Blends with iliocostalis in Transverse processes lumbar region and is of all thoracic B. Transversospinales attached to transverse vertebrae and just They run obliquely, upward, and medially from the transverse process to the processes of lumbar lateral to the tubercles spinous process filling the roof between these two vertebral projections vertebrae of the lower nine or Main function: stabilize spinal column especially segmental muscles ten ribs Found deep to the erector spinae and consist of 3 major subgroups-the Longissimus cervicis Transverse processes of Transverse process of semispinalis, multifidus and rotatores muscles. upper 4 or 5 thoracic C1 to C6 Bilateral contraction: Extension of the vertebral column vertebrae Unilateral contraction: Trunk turns/rotates in the opposite direction Longissimus capitis Transverse processes of Posterior margin of the upper four or five thoracic mastoid process Semispinalis capitis vertebrae and articular processes of lower three Bilateral contraction: pulls the head posteriorly or four cervical vertebrae Unilateral contraction: pulls the head posteriorly and turns it, causing the chin to move superiorly and turn towards the side of the contracting muscle Spinalis thoracis Spinous processes of T10 Spinous processes of or T11 to L2 T1 to T8 (varies) Muscle Origin Insertion Spinalis cervicis Lower part of ligamentum Spinous process of C2 nuchae and spinous (axis) Semispinalis Transverse processes from Spinous processes of upper process of C7 (sometimes thoracis T6 to T10 four thoracic and lower two T1 to T2) cervical vertebrae Spinalis capitis Usually blends with With semispinalis Semispinalis Transverse processes of Spinous processes of C2 semispinalis capitis capitis cervicis upper T5 or T6 (axis) to C5 Table 5. Erector Spinae Group of Back Muscles Semispinalis Transverse processes of T1 Medial area between the capitis to T6 (or T7) and C7 and superior and inferior articular processes of C4 nuchal lines of occipital to C6 bone Page 3 of 14  UNIVERSITY OF NORTHERN PHILIPPINES ANATOMY LC4b MUSCULAR SYSTEM: Trunk COLLEGE OF MEDICINE, BATCH 2026 Transcribers: Achacoso, Acosta, Ammiyao, Anulacion, Avecilla, Busaing Dr. Ana Patricia de Grano | October 2022 Editors: Baltazar, Cabillo, Sadiasa Multifidus Sacrum, origin of erectum Base of spinous processes III. SUBOCCIPITAL MUSCLES spinae, posterior superior of all vertebrae from Last group of muscles of the back iliac spine, mamillary L5 to C2 (axis) Group of deep muscles that move the head processes of lumbar Connect vertebra CI (the atlas) to vertebra CII (the axis) and connect both vertebrae, transverse vertebrae to the base of the skull processes of thoracic Form the boundaries of the suboccipital triangle: vertebrae, and articular - Medial: rectus capitis posterior major processes of lower four - Lateral: obliquus capitis superior cervical vertebrae - Inferior: obliquus capitis inferior Rotatores Transverse processes of Spinous processes of Note: lumborum lumbar vertebrae lumbar vertebrae - Rectus capitis posterior minor does not form the border of the Rotatores Transverse processes of Spinous processes of suboccipital triangle. thoracis thoracic vertebrae thoracic vertebrae - Superficial extrinsic back muscles are axio-appendicular muscles, that's Rotatores cervicis Articular processes of Spinous processes of the third upper limb except for the trapezius, innervated by cranial nerve cervical vertebrae cervical vertebrae XI (accessory nerve) Table 6. Transversospinales group of back muscles Muscle Origin Insertion Innervation Function C. Segmental Muscles Two groups innervated by posterior rami of spinal nerves. Rectus capitis Spinous Lateral Posterior Extension of posterior process of portion of ramus of C1 head, rotation First group: levatores costarum muscles major axis (C2) occipital of head same Second group -true segmental muscles of the back: bone below side of muscle - Interspinales- between adjacent spinous processes and inferior Intertransversarii- between adjacent transverse processes nuchal line Vertebral column stabilizer -allows more effective action of the large muscle group Rectus capitis Posterior Medial Posterior Extension of posterior tubercle portion of ramus of C1 head Muscle Origin Insertion Function minor of atlas occipital Levatores Short paired Small muscles Contraction elevates (C1) bone below costarum muscles arising between the rib inferior from transverse transverse nuchal line processes of C7 to processes of T11 contiguous Oblique Transvers Occipital Posterior Extension of vertebrae capitis e process bone ramus of C1 head and superior of atlas between bends it on Interspinales Short paired Postural muscles (C1) superior same side muscles attached that stabilize and inferior to the spinous adjoining vertebrae nuchal line processes of during movements contiguous of vertebral column Oblique Spinous Transverse Posterior Rotation of vertebrae, one on capitis process of process of ramus of C1 face on the each side of the inferior axis (C2) atlas (C1) same side interspinous Table 8. Suboccipital Group of Back Muscles ligament lntertransver Small muscles Postural muscles sarii between the that stabilize transverse adjoining vertebrae processes of during movements contiguous of vertebral column vertebrae Table 7: Segmental Back Muscles Figure 4. Deep Group of Back Muscles – Suboccipital Muscles Page 4 of 14  UNIVERSITY OF NORTHERN PHILIPPINES ANATOMY LC4b MUSCULAR SYSTEM: Trunk COLLEGE OF MEDICINE, BATCH 2026 Transcribers: Achacoso, Acosta, Ammiyao, Anulacion, Avecilla, Busaing Dr. Ana Patricia de Grano | October 2022 Editors: Baltazar, Cabillo, Sadiasa IV. STRAIN, SPRAIN, SPASM V. MUSCLES OF THE THORAX Axio-appendicular muscles extend from the thoracic cage (axial skeleton) A. Back sprain: only ligamentous tissue is involved, without dislocation or to bones of the upper limb (appendicular skeleton) fracture (+) excessively strong contractions related to movements of the Act primarily on the upper limbs vertebral column Pectoralis major and pectoralis minor and the inferior part of the serratus B. Back strain: common sports injury anterior, may also function as accessory muscles of respiration, helping elevate the ribs to expand the thoracic cavity when inspiration is deep and (+) overly strong muscular contraction involves some degree of forceful (e.g., after a long run) stretching or microscopic tearing of muscle fibers If the weight is not properly balanced on the vertebral column, Pectoralis major acts mainly for abduction, medial rotation and extension strain is exerted on the muscles The muscles that are involved are usually those that produce Scalene muscles movements of your lumbar intervertebral joints especially your Act primarily on the vertebral column; also serve as accessory respiratory erector spinae muscles by fixing these ribs and enabling the muscles connecting the ribs below to be more effective in elevating the lower ribs during forced When you use your back as the lever in lifting heavy weights it inspiration. puts big strain on your vertebral column on in its ligaments and muscle, it can be minimized by “lifter crouches”: wherein you Is a muscle which descends from the vertebra of the neck to the first and second of the ribs hold the back as straight as possible and use the muscle of the buttocks and your lower limbs to assist while lifting; this gives you Although external and internal Intercostal muscles are active during more balance and stronger force; instead of bending, you inspiration and expiration, most activity is isometric meaning there is crouched down a little lower to prevent putting all the strain in increase tone without producing movement the back. the roles of these muscles in producing movement of the ribs appears C. Spasm: protective mechanism after an injury or in: related to be mainly during forced respiration Response to inflammation Diaphragm is still the primary muscle of inspiration (+) sudden involuntary contraction of one or more muscle groups Expiration is passive movement unless one is exhaling against resistance Cramps, pain and interference of function and producing (e.g inflating a balloon, expel air more rapidly than usual like sneezing, involuntary movements coughing, blowing of nose or shouting) Elastic recoil of lungs and decompression of abdominal viscera expels the inhaled air Primary role of intercostal muscles is for support, increase tone or rigidity of the intercostal space to resist the paradoxical movement during inspiration when the internal thoracic pressures are lower or at the most negative A. Pectoral Region Figure 6. Muscles and Fascia of the Pectoral Region Figure 5. Back sprain, Back strain and Spasms (Nice to Know) Page 5 of 14  UNIVERSITY OF NORTHERN PHILIPPINES ANATOMY LC4b MUSCULAR SYSTEM: Trunk COLLEGE OF MEDICINE, BATCH 2026 Transcribers: Achacoso, Acosta, Ammiyao, Anulacion, Avecilla, Busaing Dr. Ana Patricia de Grano | October 2022 Editors: Baltazar, Cabillo, Sadiasa Innermost Medial edge Internal Intercostal Acts with Muscle Origin Insertion Innervation Function intercostal of costal aspect of nerves; T1- internal Pectoralis Medial half of Lateral Medial and Adduction, groove of rib superior T11 intercostal major clavicle and lip of lateral medial above margin of muscles anterior intertube pectoral nerves rotation, rib below surface of rcular and flexion Subcostales Internal Internal Related May sternum, first sulcus of of the surface surface of intercostal depress seven costal humerus humerus at second or nerves ribs (Near angle) cartilages, the of lower ribs third rib aponeurosis shoulder below joint of external Transversus Inferior Inferior Related Depresses oblique thoracis margins and aspect of intercostal costal Subclaviu Rib 1 at junction Groove Nerve to Pulls clavicle internal deep nerves cartilages s between rib on subclavius medially to surfaces of surface of and costal inferior stabilize costal body of cartilage surface sternoclavic cartilages of sternum, of ular joint; second to xiphoid middle depress tip sixth ribs process, third of of shoulder and costal clavicle cartilages Pectoralis Anterior surfaces Coracoid Medial pectoral Depresses of ribs IV- minor of process nerves tip of VII the third, fourth of shoulder; scapula protracts Table 10. Muscles of the Thoracic wall and fifth ribs, and deep fascia scapula overlying the related intercostal spaces Table 9. Muscles of the Pectoral Region B. Thoracic Wall Alter the position of the ribs and sternum and so change the thoracic volume during breathing Reinforce the thoracic wall Muscle Superior Inferior Innervation Function Attachment Attachmen t External Inferior Superior Intercostal Most active intercostal margin of rib margin of nerves; T1- during above rib below T11 inspiration; supports Figure 7. Intercostal Muscles intercostal space; VI. MUSCLES OF THE ABDOMEN moves ribs superiorly Anterolateral muscles is consist of Five muscles Internal Lateral edge Superior Intercostal Most active o Three flat muscles- external oblique, internal oblique, and transversus intercostal of costal margin of nerves; T1- during abdominis muscles groove of rib rib below T11 expiration; o Two vertical muscles- rectus abdominis and pyramidalis muscles. above deep to supports the - Each of these 5 muscles has specific actions but together they are critical intercostal for the maintenance of many normal physiological functions. By their attachmen space; positioning they form a firm but flexible wall that keeps your abdominal t of moves ribs visceral within the abdominal cavity. It protects your viscera from injury. the related inferiorly external -It also helps maintain the position of the viscera in the erect posture intercostal against the action of gravity. Page 6 of 14  UNIVERSITY OF NORTHERN PHILIPPINES ANATOMY LC4b MUSCULAR SYSTEM: Trunk COLLEGE OF MEDICINE, BATCH 2026 Transcribers: Achacoso, Acosta, Ammiyao, Anulacion, Avecilla, Busaing Dr. Ana Patricia de Grano | October 2022 Editors: Baltazar, Cabillo, Sadiasa -In addition, the contraction of these muscles assists in both quiet and force expiration by pushing the viscera upward which helps to relax the Diaphragm further into the thoracic cavity as well as in coughing and vomiting. All of these muscles also are involved in any action that increases inter abdominal pressure including parturition or childbirth, micturition or urination and expulsion of the feces from the rectum. A. DIAPHRAGM Double-domed, musculotendinous partition separating the thoracic and abdominal cavities Convex superior surface faces the thoracic cavity Concave inferior surface faces the abdominal cavity Chief muscle of inspiration Descend during inspiration (+) right and left domes; normally, the right dome is higher than the left Figure 10. Superior view of Diaphragm dome owing to the presence of the liver During the expiration, the right dome reaches as high as the 5th rib and the left dome ascends to the 5th intercostal space Crura: Musculotendinous Bands The muscular part of the diaphragm is situated peripherally with the fibers o Right crus, larger and longer than the left crus, arises from the first that converge radially on the trifoliate central aponeurotic part, known as three or four lumbar vertebrae the central tendon o Left crus arises from the first two or three lumbar vertebrae It is innervated by the Phrenic nerve o Sternal part: consists of 2 muscular slips that are attached to the The vascular group is below the interior portion of the rib, there your nerve, posterior aspect of the xiphoid process intercostal artery, intercostal vein. o Costal part: forms the right and left domes The Left and Right Crura together with median arcuate ligament will form o Lumbar part: forms right and left muscular crura that ascend to the the Aortic Hiatus central tendon Arcuate Ligaments: o Median arcuate ligament: A median tendinous arch connecting the right and left crura. o Medial arcuate ligament: On each side, connecting each crus with the tip of transverse process of L1. o Lateral arcuate ligament: On each side, connecting the tip of transverse process of L1 with the last rib. Figure 8. Apertures of the Diaphragm Figure 11. Arcuate Ligament Figure 9. Diaphragm Page 7 of 14  UNIVERSITY OF NORTHERN PHILIPPINES ANATOMY LC4b MUSCULAR SYSTEM: Trunk COLLEGE OF MEDICINE, BATCH 2026 Transcribers: Achacoso, Acosta, Ammiyao, Anulacion, Avecilla, Busaing Dr. Ana Patricia de Grano | October 2022 Editors: Baltazar, Cabillo, Sadiasa B. Function and Actions Together the muscles are critical for the maintenance of many normal physiological functions. Form a firm, but flexible, wall (keeps the abdominal viscera intact and protects it from injury, and helps maintain the anatomical position of the viscera against gravity Contraction of these muscles assists in both quiet and forced expiration by pushing the viscera upward and in coughing and vomiting. Involved in any action that increases intra-abdominal pressure- parturition, micturition and defecation. Move the trunk and help to maintain posture. Figure 12. Superficial part of the muscles of the anterior abdominal wall Figure 15. Transverse section showing the muscle layers of the abdominal wall Muscle Origin Insertion Innervation Function External Muscular Lateral lip Anterior rami Compress Oblique slips from the of Iliac of lower six abdominal outer crest; thoracic contents; surfaces of Aponeuros spinal nerves both muscles the lower is ending in (T7 to T12) flex trunk; eight ribs midline each muscle (Ribs 5 and raphe bends trunk 12) (Linea to same side, alba) turning anterior part Figure 13. Intermediate part of the muscles of the anterior abdominal wall of the abdomen to opposite side. Internal Thoracolumb Inferior Anterior rami Compress Oblique ar fascia; iliac border of of the lower abdominal crest the lower six thoracic contents; between three or spinal nerves both muscle origins of the four ribs; (T7 to T12) flex trunk; external and aponeurosi and L1 each muscle transversus; s ending in bends trunk lateral two Linea alba; and turns thirds of the pubic crest anterior part inguinal and of the ligament pectineal abdomen to line same side Figure 14. Deep part of the muscles of the anterior abdominal wall Page 8 of 14  UNIVERSITY OF NORTHERN PHILIPPINES ANATOMY LC4b MUSCULAR SYSTEM: Trunk COLLEGE OF MEDICINE, BATCH 2026 Transcribers: Achacoso, Acosta, Ammiyao, Anulacion, Avecilla, Busaing Dr. Ana Patricia de Grano | October 2022 Editors: Baltazar, Cabillo, Sadiasa Transversu Thoracolumb Aponeuros Anterior rami Compress s ar fascia; is ending in of lower six abdominal C. Rectus Sheath, Linea Alba, and Umbilical Ring Abdominis medial lip of Linea alba; thoracic contents Rectus Sheath- encloses the muscle iliac crest; pubic crest spinal nerves Strong, incomplete fibrous compartment of the rectus abdominis and lateral one- and (T7 to T12) pyramidalis muscles third of pectineal and L1 They are also found in your rectus sheath in superior and inferior inguinal line epigastric arteries and veins together with your lymphatic vessels and ligament; some of your abdominal nerves. costal Formed by the decussation and interweaving of the aponeuroses of the cartilages flat abdominal muscles lower six ribs Has an anterior and posterior wall for most of its length: (ribs VII to o The anterior wall is formed by the aponeuroses of the external oblique, XII) and of half of the internal oblique. Rectus Pubic crest, Costal Anterior rami Compress o The posterior wall is formed by the aponeuroses of half the internal abdominis pubic cartilages of lower abdominal oblique and of the transversus abdominis. tubercle, and of ribs 5 to seven contents; 1/3 of the distance between the umbilicus and the pubic symphysis- only an pubic 7; xiphoid thoracic flex vertebral anterior wall exists; the rectus abdominis is in direct contact with the symphysis process spinal nerves column; transversalis fascia. (T7 to T12) tense abdominal The demarcation point where the posterior wall ends is called the arcuate wall line. Pyramidali Front of Into Linea Anterior rami Tenses the Fibers of the anterior and posterior layers of the sheath interlace in the s pubis and alba of T12 Linea alba anterior median line to form the complex linea alba. pubic The posterior layer of the rectus sheath is also deficient superior to the symphysis costal margin Table 11. Abdominal wall muscles At its middle, underlying the umbilicus, the Linea alba contains the umbilical ring - Anterolateral abdominal muscles are involved in the movement of the o defect in the linea alba through which the fetal umbilical vessels passed trunk at the level of your lumbar vertebrae and as well as in controlling to and from the umbilical cord and placenta the tilt of your pelvis when you are standing for the maintenance of o All layers of the anterolateral abdominal wall fuse at the umbilicus. posture - Abdominal muscles are responsible for resisting the lumbar lordosis. Linea Semilunaris: is a vertical, curved structure that runs along the lateral - The lumbar vertebrae resist from exaggerating lordotic position. edges of the rectus abdominis muscle in the anterior abdominal wall. - Consequently, when strengthening the anterolateral abdominal wall Conjoint Tendon: is a sheath of connective tissue formed from the lower musculature that will improve standing and sitting posture. part of the common aponeurosis of the abdominal internal oblique muscle Rectus abdominis is a powerful flexor of the thoracic and specially the lumbar and the transversus abdominis muscle, joining the muscle to the pelvis. region. It pulls the anterior costal margin and pubic crest towards each other. o Confluence of the internal oblique and transverse abdominis fibers, which strengthen the medial half of the posterior wall of the inguinal Oblique abdominal muscles assist in the movement of the trunk especially in canal the lateral flexion and the rotation of the thoracic vertebral column. Approximately 80% of people would have insignificant pyramidalis which is located on the rectus sheath anterior to the most inferior part of rectus abdominis, a small muscle draws down on the linea alba, this muscle acts as an antagonist of the diaphragm to produce expiration Figure 17. Organization of the Rectus Sheath. (A) Transverse section through the upper three-quarters of the rectus sheath. (B) Transverse section through the lower one-quarter of the rectus sheath. Figure 16. Posterolateral View of Abdominal Muscles Page 9 of 14  UNIVERSITY OF NORTHERN PHILIPPINES ANATOMY LC4b MUSCULAR SYSTEM: Trunk COLLEGE OF MEDICINE, BATCH 2026 Transcribers: Achacoso, Acosta, Ammiyao, Anulacion, Avecilla, Busaing Dr. Ana Patricia de Grano | October 2022 Editors: Baltazar, Cabillo, Sadiasa D. Posterior Abdominal Wall Iliacus Superior two Lesser Femoral Flexes thigh The relationship between the aponeurotic muscle sheets and the fascia thirds of iliac trochanter of nerve (L2- and stabilizes and the abdominal wall are demonstrated in transverse section. fossa, ala of femur and L4). hip joint; acts The Three flat abdominal muscles forming the lateral wall span between sacrum, and shaft inferior with psoas the anterior and the posterior aponeurotic formation that in sheet anterior to t and to major vertically dispose muscles so the thin anterolateral walls are distensible sacro-iliac psoas major although flexible posterior abdominal wall is wavering (??? Loom part 2: ligaments. tendon 16.18mins) and so in reinforce by the vertebral column and muscles that Quadrat Medial half Ilolumbar Anterior Extends and act on it. Thus, it is not distensible. us of inferior ligament and branches of laterally Posterior abdominal wall is not distensible compared to anterolateral Lumbor border of internal lip of T12 and L1- flexes wall. um 12th ribs and iliac crest L4 nerves. vertebral tips of column; fixes lumbar 12th rib transverse during processes inspiration. Table 12. Posterior Abdominal Wall Muscles Figure 18. Inferior View and Transverse Section of Abdominal Muscles Muscle Origin Insertion Nerve Function Innervation Figure 19. Psoas Muscle Psoas Transverse By iliacus Anterior rami Acting major processes of tendon to of lumbar inferior with lumbar lesser nerves L1, L2 iliacus, it VII. PELVIS vertebrae; trochanter of and L3 flexes the side of femur. thigh; acting Pelvis (L. basin) bodies of superiorly. It T12-L5 flexes the Area of transition between the trunk and the lower limbs. vertebrae vertebral Muscles of the Pelvic Floor and column o The pelvic floor is formed by the bowl or funnel-shaped pelvic intervening laterally; it is diaphragm (coccygeus and levator ani muscles + fascias) intervertebra used to o The pelvic diaphragm lies within the lesser pelvis, separating the pelvic l discs. balance the cavity from the perineum, for which it forms the roof. trunk with Functions: the o Support the organs of the pelvic cavity iliacus to flex o Flex the sacrum and coccyx the trunk. o Control the movement of materials through the urethra and anus Psoas Lateral Pectineal line Anterior rami Weak flexion minor surface of of the pelvic L1 of lumbar Muscle Origin Insertion Nerve Function bodies of T12 brim and vertebral Innervation and L1 iliopubic column Obturator Anterolate Medial Nerve to Latera l vertebrae eminence internus ral wall of surface of obturator rotation of and true greater internus the extended intervening pelvis trochanter L5, S1 hip joint; intervertebra (deep of femur abduction of l disc surface of flexed hip Page 10 of 14  UNIVERSITY OF NORTHERN PHILIPPINES ANATOMY LC4b MUSCULAR SYSTEM: Trunk COLLEGE OF MEDICINE, BATCH 2026 Transcribers: Achacoso, Acosta, Ammiyao, Anulacion, Avecilla, Busaing Dr. Ana Patricia de Grano | October 2022 Editors: Baltazar, Cabillo, Sadiasa obturator membrane and surroundin g bone) Piriformis Anterior Medial side Branches Latera l surface of of superior from S1, and rotation of sacrum border S2 the extended between of greater hip joint; anterior trochanter abduction of sacral of femur flexed hip foramina Table 13. Muscle of the Pelvic Wall VIII. PERINEUM Muscle Origin Insertion Nerve Function Innervation Figure 20. Muscle of the Pelvic wall Levator ani In a line The Branches Contributes around the anterior direct from to the - Lies below the pelvic diaphragm. pelvic will part is the anterior formation “Diamond-shaped” structure between the external genitalia beginning on attached ramus of S4, of and the anus. the to the and by the the pelvic BOUNDARIES: posterior superior inferior rectal floor, which o Anterior – pubic symphysis aspect of surface of branch of the supports o Posterior – tip of coccyx the pubic the pudendal the pelvic o Lateral – inferior pubic rami and inferior ischial rami, and bone perineal nerve (S2 to viscera; sacrotuberous ligament and mem S4) maintains o Roof – pelvic floor extending brane; the a n angle o Base – skin and fascia across the posterior between obturator part meets the rectum SURFACE BORDERS internus its and anal o Anterior: mons pubis in females, base of penis in males muscle as partner on canal; o Lateral: medial surfaces of the thighs a tendinous the other reinforces o Posterior: superior end of the intergluteal cleft. arch side the (thickening at the external of the perineal anal obturator body, sphincter intern us around and, in fascia) to the the anal women, ischial spine canal, and functions along as a vaginal the sphincter anococcyge al ligament Coccygeus Ischial spine Lateral Branches Contributes and pelvic margin of from the to the surface coccyx and anterior formation Figure 21. Boundaries of Perineal Muscles of the related rami of S3 of sacrospinous border of and S4 the pelvic - Muscles of pelvic floor form the perineal region: area divided into the anal ligament sacrum floor, which triangle (posterior) and urogenital triangle (anterior) supports Urogenital Triangle: contains the roots of external genitalia, the pelvic and in women, the openings of the urethra and the vagina. In viscera; men, the distal part of the urethra is enclosed by erectile pulls coccyx tissues and opens at the end of the penis. forward o In both sexes, the urogenital triangle is divided into superficial and deep perineal space called Perineal after Membranes. defecation Anal Triangle: contains anus and external anal sphincter. Table 14. Muscles of the Pelvic Diaphragm o No difference in the female and male deep perineal musculature. Page 11 of 14  UNIVERSITY OF NORTHERN PHILIPPINES ANATOMY LC4b MUSCULAR SYSTEM: Trunk COLLEGE OF MEDICINE, BATCH 2026 Transcribers: Achacoso, Acosta, Ammiyao, Anulacion, Avecilla, Busaing Dr. Ana Patricia de Grano | October 2022 Editors: Baltazar, Cabillo, Sadiasa pelvic cavity even though the perineal membrane and the deep perineal pouch are usually considered parts of the perineum. Figure 22. Perineum. (A) In women. (B) In men. Figure 23. Muscles in Deep Perineal Pouch. (A) In women. (B) In Men. Nerve Muscle Origin Insertion Function Perineal Membrane & Adjacent Pubic Arch: Innervation provide attachment for the roots of the external genitalia External anal sphincter and the muscles associated with them. Deep Part Surrounds Pudendal Closes anal superior nerve (S2 and canal aspect of S3) anal canal and branches directly from S4 Superficial Surrounds Anchored Part lower part to perineal of anal body canal and anococcyge al body Subcutaneou Surrounds s part anal aperture Table 15. Muscle of the Anal Triangle A. Deep Perineal Pouch Is open above and is not separated from more superior structures by a distinct layer of fascia. The parts of the perineal membrane and structures in the deep perineal Figure 24. Perineal Membrane and Deep Perineal Pouch. (C) Medial View space are enclosed by the urogenital hiatus above therefore they contributed to the pelvic floor and is part of the urogenital system in the Page 12 of 14  UNIVERSITY OF NORTHERN PHILIPPINES ANATOMY LC4b MUSCULAR SYSTEM: Trunk COLLEGE OF MEDICINE, BATCH 2026 Transcribers: Achacoso, Acosta, Ammiyao, Anulacion, Avecilla, Busaing Dr. Ana Patricia de Grano | October 2022 Editors: Baltazar, Cabillo, Sadiasa Muscle Origin Insertion Nerve Function Innervation External From the Surrounds Perineal Compresse urethral inferior membrano branches of s the sphincter ramus of us parts of the Pudendal membrano the pubis the urethra Nerve (S2 to us urethra; on each S4) relaxes side and during adjacent micturition walls of the deep perineal pouch Deep Medial Perineal Perineal Stabilize Transverse aspect of Body branches of the Figure 25. Muscles in the superficial Perineal Pouch. (A) In Women. (B) In Men. Perineal ischial the position of ramus Pudendal the Nerve (S2 to perineal Muscle Origin Insertion Nerve Function S4) body Innervation Compressor Ischiopubic Blends with Perineal Functions Ischiocaverno Ischial Crus of Pudendal Move blood urethrae ramus on partner on branches of as an sus tuberosity penis and nerve from crura (only in each side other side the accessory and ramus clitoris (S2 to S4) into the women) anterior to Pudendal sphincter body of the urethra Nerve (S2 to of the erect penis S4) urethra and clitoris Sphincter Perineal Passes Perineal Functions Bulbospongio In women: In women: Pudendal Move blood urethrovagin Body forward branches of as an sus perineal bulb of nerve from alis (only in lateral to the accessory body vestibule, (S2 to S4) attached women) vagina to Pudendal sphincter In men: perineal parts of blend with Nerve (S2 to of the perineal membrane, the clitoris partner on S4) urethra body, body of and penis the other (also may midline clitoris, and into the side facilitate raphe corpus glans anterior to closing the cavernosum In men: the urethra vagina) removal of In men: Table 16. Muscles within the Deep Perineal Pouch bulbospongi residual osus, urine B. Superficial Perineal Pouch perineal from urethra Contains the space that lies beneath the skin of the perineum. membrane, after Skeletal muscles are associated mainly with the rectal structures corpus urination; attached to the perineal membrane and adjacent bones. cavernosum pulsatile emission of semen d u ring ejaculation Superficial Ischial Perinea l Pudendal Stabilize the transverse tuberosity body nerve perineal perineal and ramus (S2 to S4) body Table 17. Muscles of the Superficial Perineal Pouch C. Injury to Pelvic Floor During childbirth, the pelvic floor supports the fetal head while the cervix of the uterus is dilating to permit the delivery of the fetus. Perineum, levator ani, and ligaments of the pelvic fascia may be injured during childbirth Most often torn muscles: pubococcygeus and puborectalis Page 13 of 14  UNIVERSITY OF NORTHERN PHILIPPINES ANATOMY LC4b MUSCULAR SYSTEM: Trunk COLLEGE OF MEDICINE, BATCH 2026 Transcribers: Achacoso, Acosta, Ammiyao, Anulacion, Avecilla, Busaing Dr. Ana Patricia de Grano | October 2022 Editors: Baltazar, Cabillo, Sadiasa Weakening of the levator ani and pelvic fascia may decrease support for 3. Elevates ribs II to V. This is the most well-developed group of muscles in the vagina, bladder, uterus, or rectum or alter the position of the neck of swimmers the bladder and the urethra A. Serratus posterior May cause urinary stress incontinence or lead to the prolapse of one or B. Serratus anterior more pelvic organs. C. Multifidus D. Illiocostalis Tearing of the puborectalis→ leads to fecal incontinence. 4. Which of the following muscles tenses the linea alba? A. External obliquie B. Rectus abdominis C. Pyramidalis D. Internal oblique 5. The anterolateral muscles consist of five muscles. Which of the following comprises the three flat muscles? A. Rectus abdominis, External oblique, Internal oblique B. External oblique, Transverse abdominis, Internal oblique C. Transverse abdominis, External oblique, Internal oblique D. Pyramidalis muscles, External oblique, Internal oblique 6. What is the chief muscle of inspiration? A. Erector Spinae Muscles B. Levator Ani C. Pyramidalis muscles D. Diaphragm 7. It is formed by the aponeuroses of half the internal oblique of the transversus abdominis. A. Posterior wall B. Transversalis fascia C. Anterior wall D. Rectus sheath 8. During child birth, except… A. Levator ani is torn Figure 26. (A)Tear of perineum and (B) Tear of pubococcygeus during childbirth B. Dilated uterus C. Dilated pubococcygeus REFERENCE D. Urine incontinence Drake, R., Vogl, W., Mitchell, A. and Gray, H., 2005. Gray's anatomy for students. Philadelphia: Elsevier/Churchill Livingstone. 9. Lateral boundary of the pelvic diaphragm between external genitalia and the Moore, K. L., Dalley, A. F., & Agur, A. (2017). Clinically oriented anatomy (8th ed.). anus… Lippincott Williams and Wilkins. A. Pelvic floor Netter, F. H. 1. (2014). Atlas of Human Anatomy. Seventh edition. Philadelphia, PA, B. Inferior ischia rami Saunders/Elsevier. C. Skin and fascia D. Coccyx tip SAMPLE QUESTIONS 10. Aponeuroses in ending in Linea alba, except… A. External oblique 1. Only ligamentous tissue is involved, without dislocation or fracture B. Internal oblique A. Back strain B. Back sprain C. Rectus abdominis C. Spasm D. Transverse abdominis D. Cramps 2. Draw and rotate head to one side (turn face to same side) A. Spinalis cervicis B. Splenius cervicis C. Splenius capitis D. Longisimus capitis 1. B 2. C 3. A 4. C 5. B 6. D 7. A 8. C 9. B 10. C Answers: Page 14 of 14