（二） masticatory muscles masseter ： Origin － inferior border and medial surface of zygomatic arch Insertion － lateral surface of ramus of mandible and angle of mandible temporalis ： Origin － temporal fossa Insertion － coronoid process of mandible action ： masseter, temporalis --- elevates mandible— close the mouth
（二） masticatory muscles action ： medial pterygoid --- elevates mandible—close the mouth lateral pterygoid ： pull the head of mandible forwards--- open the mouth medial pterygoid ： lateral pterygoid ：
Ⅱ. Muscles of neck
Sternocleidomastoid Platysma Origins: manubrium and medial1/3 of clavicle Insertion: mastoid process of temporal bone; Actions: acting alone, the head is inclined ipsilateral and the face is rotated to opposite side; acting together, they extend the head.
1 、 lateral goup scalenus anterior scalenus medius scalenus posterior 2 、 medial group ： longus colli longus capitis scalene fissure ： it is bounded by the scalenus anterior and medius and first rib ， it contains the subclavian a and brachial plexus. （三） The deep cervical m.
section 3 The muscles of trunk
Ⅰ. The muscles of back
（ 1 ） Trapezius a large, triangular m. lying on the back of the neck and thorax; Origin: external occipital protuberance, superior nuchal line, ligamentum nuchae, the spinous processes of 7 th cervical vertebrae and all thoracic vertebrae; trapezius 1 、 superficial group Insertion: lateral 1/3 of clavicle, acromion and spine of scapula.
（ 1 ） Trapezius trapezius 1 、 superficial group Action ： raises, descends, and rotates the scapula and extends the head.
（ 2 ） Latissimus Dorsi It is a largest and triangular m. lying the back and lateral wall of thorax; Origins: the spinous processes of lower 6 thoracic vertebrae and all lumbar vertebrae; Insertion : inserted into the floor of the intertubercular sulcus Action: Extend, adduct ， and rotate the shoulder joint medially Latissimus dorsi 1 、 superficial group
Levator scapulae Rhomboideus （ 3 ） levator scapulae origin ： the transverse processes of the upper 4 cervical vertebrae; insertion ： superior angle of scapula. Action ： raise the scapula. （ 4 ） rhomboideus Lies deep to the trapezius ， 1 、 superficial group
2 、 The deep group position ： It lies in the vertebral groove on each side of vertebral spines; Action ： extend the spinal column and head Splenius position ： Action ： Erector Spinae
Ⅱ. The muscles of thorax
1. Extrinsic muscles Pectoralis major Pectoralis minor Serratus anterior
Pectoralis major Origin: medial half of clavicle,sternum,1th-6th costal cartilages. Insertion: crest of greater tubercle of humerus. Action: flexes, adducts and rotates arm medially; arm fixed, elevates trunk; elevates ribs 1-6,aidding in forced inspiration.
Pectoralis minor Deep to the pectoralis major Origin: 3rd-5th ribs Insertion: coracoid process of scapula Action: Draw the scapula forwards and downwards,when the scapula is fixed it helps the inspiration(by elevation the ribs)
Serratus anterior It overlies the laeral wall of thorax Origin: external surfaces of the upper 8~9 ribs Insertion: medial border of scapula Action: holds the scapula against the chest wall ； Pulls the scapula forwards in throwing and pushing.
Intercostales externi Origin: lower border of rib Insertion: upper border of rib below origin external intercostals membrane. Action: elevate ribs adding in forced inspiration 2. Intrinsic muscles
Origin: upper border of rib ； Insertion: lower border of rib above origin Replaced posteriorly by internal intercostals membrane. Action: depress ribs for forced expiration Intercostales interni
(1) Position and division : dome-shaped between thorax and abdomen, consists of Central tendon muscular part Ⅲ. Diaphragm Sternal part: Costal part: Lumbar part: arises by left and right crus from upper 2-3 lumbar vertebrae Insertion : central tendon
(2) Openings of diaphragm ① Aortic hiatus at the level of 12th thoracic vertebra, the thoracic aorta and thoracic duct pass through it ② Esophageal hiatus at the level of 10th thoracic vertebra, the esophagus and vagus n. pass throught it ③ Vena caval foramen at the level of 8th thoracic vertebra, inferior vena cava through it T8 T10 T12 inferior vena cava esophagus thoracic aorta
(3) Action Contraction: the dome moving downward, increases the volume of thoracic cavity which results in inspiration. Relaxation: the dome returns to the former position, reduces the volume of the thoracic cavity, resulting in expiration.
(2) Weak areas: triangular spaces without muscular tissue Lumbocostal triangle between costal and lumbar parts. Sternocostal triangle between costal and sternal parts.
Muscles of abdomen Anterolateral group Obliquus externus abdominis Obliquus internus abdominis Transversus abdominis Rectus abdominis
Obliquus externus abdominis Origin: Arises from the lower 8 ribs, and the muscular fibers run obliquely from the superolateal to the inferomedial, the anterior part of the m. change gradually into aponeurosis, which pass over the rectus Abdominis; insertion: Linea alba.
Obliquus externus absominis Structures formed by aponeurosis of this m. include ： Inguinal ligament Superficial inguinal ring triangular-shaped hiatus above pubic tubercle Lacunar ligament Superficial inguinal ring Lacunar ligament
Obliquus internus abdominis Origin: thoracolumbar fascia, iliac crest and the lateral half of the ingunal lig. Insertion: Linea alba The muscular fibers run upwards and forwards, and become the aponeurosis close the lateral border of the rectus abdominis. Its aponeurosis divided into two layers to inclose the rectus abdominis.
Transversels abdominis Origin: it arises from the costal cartilages of the lower 6 ribs ， the thoracolumbar fascia, the iliac crest and the lateral 1/3 of the ingunal lig., is the deepest one of the three flat abdominal m. Insertion : Linea alba The muscular fibers run transversly,and pass deep to rectus abdominis.
Inguinal falx(conjoined tendon) or is a common aponeurosis joined by obliquus internus abdominis and transverse abdomini, it turns downwards to insert the pubic crest and pecten pubis. Cremaster : around the spermatic cord and testis Transversels abdominis
The Sheath of rectus abdominis Anterior layer － formed by the aponeurosis of obliquus externus abdominis ； anterior leaf of aponeurosis of obliquus internus abdominis Posterior layer ： formed by posterion leaf of aponeurosis of obliquus internus abdominis ； aponeurosis of transverses abdominis
The Sheath of rectus abdominis arcuate line semicircular line at about 4-5cm below the umbilicus, the lower free border of the posterior layer of the sheth present arcuated. Below this line the rectus abdominis in contact with transverse fascia directly.
Linea alba － tendinous raphe between right and left rectus abdominis from xiphoid process to pubic symphysis.
The functions of the four pairs of muscles Support and protect the abdominal viscera Maintain and increase intra- abdominal pressure, aid in vomiting, coughing, sneezing, defecation, urination and childbirth. Flex, lateral flex, and rotate vertebral column
Posterior group Quadratus lumborum Psoas major
Inguinal canal Position: oblique passage about 4cm long, and passes downwards and medially, it lies parallel to, and immediately above medial half of inguinal lig. It has two openings and four walls.
Four walls Anterior wall Aponeurosis of obliquus externus abdominis Obliquus internus abdominis (lateral third of wall)
Post wall — Transverse fascia ； Inguinal flax medially Roof － lower fibers of obliquus internus and transversus abdominis Floor － inguinal ligament ．
Two openings Superficial inguinal ring Deep inguinal ring defect in transverse fascia ， lies at about 1.5cm above midpoint of inguinal ligament
Structures passing through the inguinal canal Male : Spermatic cord female: Round ligament of uterus