ANAT 200 - Muscular System

Midterm #1, Winter 2023

axial musculature

associated with the axial skeleton (skull, vertebral column, and ribs)

What are the main characteristics of axial musculature?

* innervation by cranial nerves (CNs) or spinal nerves 
* attachments on axial skeleton, associated organs (e.g. eyeball), or soft tissue (skin of face)

What are the major functions of the axial skeleton?

* vision, mastication, facial expression, and swallowing 
* upright posture and movement of the back 
* support of abdominal and pelvic viscera 
* respiration 
* urination, defecation, and partuition 

What are the major groups of the axial skeleton?

* muscles of the head and neck (face, oral, cavity, pharynx, and larynx)
* muscles of the back 
* muscles of the thorax and abdominopelvic cavities 
* muscles of the pelvis and perineum 

appendicular musculature

associated with the appendicular skeleton (limb bones, including should and pelvic girdles)

What are 6 head and neck muscles?

* extraocular muscles
* muscles of mastication
* muscles of facial expression
* pharyngeal muscles
* tongue msucles
* neck muscles

extraocular muscles

innervated by oculomotor (CN III), trochlear (CN IV), and abducens nn. (CN VI)

What are 7 extraocular muscles?

* levator palpebras superioris
* superior rectus
* medial rectus
* inferior rectus
* lateral rectus
* inferior oblique
* superior oblique

Levator palpebras superioris

CN III; pulls eyelid up; attches to eyelid

Superior rectus

CN III; look up

Medial rectus

CN III; side to side

Inferior rectus

CN III; look down

Lateral restus

CN VI; side to side

Inferior oblique

CN III; look up

Superior oblique

CN IV; look down

CN VI palsy

lateral rectus is paralyzed on right side fo the patient

muscles of mastication

innervated by trigeminal n. (CN V**3**)

What are 4 muscles of mastication?

* temporalis
* masseter
* lateral pterygoid muscle
* medial pterygoid muscle

Temporalis

attaches on frontal bone, parietal bone, temporal bone and through zygomatic arch to the coronoid process of the mandible; elevator of mandible when chewing on food and closing mouth

Masseter

attaches on zygomatic arch and ramus of mandible; elevator of mandible when chewing on food and clsoign mouth

Lateral pterygoid muscle

attach on pterygoid plate of sphenoid bone; depressor of mandible to open mouth; can also move mandible side

Medial pterygoid muscle

attach on pterygoid plate of sphenoid bone; elevator of mandible when chewing on food and closing mouth

What are the biomechanics of chewing?

muscles of facial expression

innervated by facial n. (CN VII)

What are 5 muscles of facial expression?

* orbicularis oculi
* orbicularis oris
* platysma
* occipitofrontalis (frontal belly)
* buccinato

Orbicularis oculi

closes eyelids

Orbicularis oris

purses lips; kissing

Platysma

tenses skin of neck

Occipitofrontalis (frontal belly)

raises eyebrows, wrinkles forehead

Buccinato

tenses cheeks, suction

Bell’s palsy

damage to facial nerve (CN VII); right side of the face sags

pharyngeal muscles

innervated mostly by vagus n. (CN X); involved in swallowing

What are 4 pharyngeal muscles

* tensor and levator veli palatini
* superior constrictor
* middle constrictor
* inferior constrictor

Tensor and levator veli palatini

tenses and elevates soft palate

Superior constrictor

constriction of pharynx

Middle constrictor

constriction of pharynx

Inferior constrictor

constriction of pharynx

tongue muscles

innervated mostly by hypoglossal n. (CN XII); glossus in name = tongue muscle

What are the 4 tongue muscles

* palatoglossus
* styloglossus
* hyoglossus
* genioglossus

What do the 4 tongue muscles do?

control position of tongue

Which tongue muscle has an attachment on the hyoid bone?

hyoglossus

neck muscles

innervated by CNs or cervical nn.

What are the 6 muscles of the neck?

* mylohyoid
* diagastric
* infrahyoid mm,
* sternocleidomastoid
* longus colli
* scalene mm.

Mylohyoid

tenses floor of mouth during swallowing

Diagastric

has 2 bellies; assists in depression of mandible to open mouth wide; attach to hyoid

Infrahyoid mm.

there are 4; pull down hyoid bone

Sternocleidomastoid

turns head to opposite side of contraction; attaches to sternum, clavicle, and mastoid process

Longus capitis

flexor of neck and head

Longus colli

flexor of neck

Scalene mm.

lateral flexor of neck; elevators of ribs 1 and 2

What are the biomechanics of swallowing?

1. contraction of mylohyoid and tongue muscles to move tongue up and back  
2. contraction of tensor and levator veli palatini muscles - elevates and stretches soft palate so nothing enters nasal cavity 
3. elevation of larynx by many muscles so the food does not go into airway 
4. sequential contraction from top the top of constrictor muscles - bring food down neck

What are 2 back muscles?

* transverospinal group
* erector spinae

transverospinal group

delicate adjustments at zygapophyseal joints of vertebrae; can be source of back pain 

erector spinae

extensors of back; allows trunk to remain in vertical position

What are the 3 erector spinae muscles?

* longissimus  
* spinalis  
* iliocostalis

What are 4 muscles of the trunk?

* intercostal muscles mm.
* rectus abdominis
* abdominal mm.
* diaphragm

intercostal muscles mm.

3 different layers; most superficial are elevators of ribs during respiration (inhalation phase)

intercostal contraction during respiration

contraction of intercostal mm. produces elevation of ribs; increases volume of thoracic cavity 

rectus abdominis

flexors of trunk

What are the 3 layers of the abdominal mm.

* 2 obliques
* 1 transverse

external and internal abdominal obliques

flexors, lateral flexors, and rotators of trunk 

transversus abdominis

deepest muscle on the side; used to compress 

What can all abdominal mm. do?

increase intra-abdominal pressure (during defecation, urination, parturition, loud singing, etc)

diaphragm

separates thoracic and abdominal cavities; chief muscle of respiration; innervated by phranic n. (C3-C5 levels of spinal cord)

What are the 3 parts of the diaphragm

* central tendon
* muscle fibers
* crura

central tendon

brought down each time you breath in 

muscle fibers

attach to sternum, ribs, central tendon; in back for cris or crura in back 

crura

legs of diaphragm

What 3 things does the diaphragm have an opening for?

* inferior vena cava
* esophagus
* aort

Inferior vena cava

brings blood from the lower extremities and abdomen to heart

Esophagus

brings food to stomach

Aort

blood from the heart to support body

Contraction

relaxation of diaphragm during exhalation phase of respiration; contraction of diaphragm during inhalation phase of respiration; brings central tendon down to increase volume of thoracic cavity

What are 2 muscles of the pelvis?

* coccygeus
* levator ani

What do the 2 pelvic muscles do?

form the pelvic diaphragm (pelvic floor); provide support to pelvic viscera such as urinary bladder, rectum, uterus (female), prostate gland (male)

What are 4 perineal muscles?

* external anal sphincter
* external urethral sphincter
* bulbospongiosus
* ischiocavernosus

External anal sphincter

regulates anal opening (fecal continence); under voluntary control; innervated by pudendal n.

External urethral sphincter

regulates urethral opening (urinary continence); more developed in males; innervated by pudendal n.

What so the bulbospongiosus and ischiocavernosus do?

contraction increases blood flow into erectile tissues of genitalia; innervated by pudendal n.

What are the major characteristics of the appendicular musculature?

* innervation by spinal nerves forming plexuses (with exception of trapezius - CN XI)


* attachments on axial and appendicular skeleton 


* movements - muscle contraction causes a limb segment to move in a specific plane at a given joint (e.g. contraction of quadriceps femoris extends the leg at the knee joint)

How are limb muscles organized?

in compartments (each muscle compartment is innervated by a specific nerve branch of a plexus)

What are major characteristics of upper limb musculature?

* innervated by branches of brachial plexus (levels C5 to T1 of psinal cord), except trapezius (CN XI)
* four major muscle groups crossing upper limb joints: shoulder (pectorial girdle), arm, forearm, and hand

What are major functions of upper limb musculature?

Upper limb joints are designed for mobility (rather than stability); reaching, throwing, grasping, and manipulating are all important functional roles of the upper limb

* Muscles positioning the pectoral girdle
* Muscles moving the arm
* Muscles moving the forearm and hand
* Muscles moving the hand and digits

What 9 muscles move the pectoral girdle?

* trapezius
* levator scapulae
* rhomboids
* serratus anterior
* deltoideus
* pectoralic major
* latissimus dorsi
* rotator cuff muscles
* teres major

Trapezius

multiple actions depending on the fibre orientation (elevator, retractor, and depressor of scapula)

Upper fibers

when contracts pulls the scapula up

Lowers fibers

when contracts pull it down and to the side

Levator scapulae

elevator of scapula; attaches to vertebral column of neck and superior medial border of scapula

Rhomboids

retractors of scapula; attaches to

Serratus anterior

protractor of scapula; bulk of muscle goes from ribs to anterior aspect of the scapula; attaches along medial vertebral border of scapula; pulls scapula down

Force couple

muscles working together to do something they could not otherwise do (e.g. trapexius and serratus anterior)

Deltoideus

major arm abductor; arm flexor and medial rotator (anterior part) on posterior side arm extensor and lateral rotator (posterior part)

Pectoralix major

arm abductor, flexor, and medial rotator

Latissimus dorsi

powerful arm retractor; arm extensor, adductor, and medial rotator; attaches to; crosses shoulder joint underneath

Rotator cuff muscles:

tendons of SITS muscles reinforce should joint capsule and hold the humeral head against glenoid fossa (preventing dislocation of the shoulder joint)

What are the 4 rotator cuff mucles?

* supraspinatus
* infraspinatis
* subscapularis
* teres minor

Supraspinatus

arm abductor (assists deltoid)

Infraspinatis

arm lateral rotator

Subscapularis

arm medial rotator; on anterior aspect of scapula in subscapular fossa; one of 4 muscles known as the rotator cuff

Teres minor

arm lateral rotator