Muscular System I (Head & Neck)

Question 1

What are the 3 Types of Muscular Tissue?

Answer 1

• cardiac muscle fibers - exclusively seen in heart
• smooth muscles fibers or tissue which are found in the wall of hollow viscera and in wall of blood vessels
  ◦ both of them are controlled by
  the autonomic nervous system
  (visceral)
• skeletal muscle tissue - contraction of skeletal muscles is controlled by the somatic nervous system

Question 2

Skeletal Muscles Nomenclature

Answer 2

• shape: rhomboid (diamond shape), trapezius (triangular shape), deltoid
• location: pectoralis (sitting in front of chest), intercostal (muscle sitting between the ribs), brachialis
• attachments: sternocleoidmastoid (SCM), stylohyoid
  ◦ sternum, clavicle and mastoid process in temporal bone and the second one runs between styloid process of temporal bone and hyoid bone (two attachements)
• number of heads: biceps brachii (2 head as its origin), quadriceps femoris
• function: extensor digitorum (extending the digits), erector spinae (erects or extends your spine)- common criteria to name the muscles (like flexor and extensor muscles
• direction of fibers: transversus abdominis, (indicates that the fibers of this muscle are running horizontally and is a muscle in abdomen) rectus capitis (straight muscles which with vertical straight muscle fibers that go from your cervical vertebrae to the base of your skull) - rectus (straight) capitis (head)
• size: gluteus maximimus (location: gluteal region and largest gluteal muscle), vastus medialis (broad muscle on medial side of the thig

Question 3

4 Main Pieces of Information for Any Given Muscle

Answer 3

• origin: that attachment of the muscle that remains stationary during muscle contraction (usually does not move)
  ◦ the bone that the muscle attaches to should not move - origin has nothing to do with being the proximal or distal attachment rather it is simply the attachment of the muscle which will not move when the muscle contracts
• insertion: that attachment of the muscle that usually moves as the result of muscle contraction - opposite of origin
• function: moving the insertion toward the origin or putting them in the same plane - when muscles contract they become shorter and tend to do two different things - either bring insertion closer to origin or bring insertion to same anatomical plane as the origin (sometimes muscles do both at the same time)
• innervation: peripheral component of the somatic nervous system - nerve supply - when nerve is damaged which muscles is paralyzed as a result?

Question 4

What are the two main categories for muscles of the head?

Answer 4

• can divide or classify the muscles of the head region into two main categories - one group of these muscles are in the face and the other group of muscles in sitting in deep parts of the head such as your oral cavity
• within the face you can divide into two categories: superficial muscles of the face which are the same group of muscles that are known as muscles of expression - these muscles have one attachment to one of the bones of the skull and the other end of them attaches to the skin, deep surface of the skin
  ◦ when these muscles contract
  they can change your facial
  expressions
  Deep Muscles of the Face
• these muscles do have attachments to your mandible and so they can move your mandible in different directions - all those movements are necessary for chewing - deep muscles are introduced as muscles of mastication (chewing)

Question 5

Occipito-frontalis (epicranius)

Answer 5

• on top of the head region is a muscle called occipito-frontalis (epicranius) - muscle has two pieces one in the occipital region and one in the frontal region and it is on top of the cranium
  ◦ there is a frontal belly and occipital belly which are not completely separate as they are connected together by a wide, flat layer of dense connective tissue which is known was epicranial aponeurosis - connecting two bellies of this muscle - most people can only control the frontal muscle which attaches to the skin of your forehead and raises your eyebrows and puts wrinkles in your forehead
• when frontal and occipital belly work together some people can move the skin on their scalp, on top of their head and they can move the hairs there
• all superficial muscles of the face are innervated by cranial nerve VII (7)

Question 6

Orbicularis oculi

Answer 6

encircles around your orbital cavity (first word describes the shape of the fibers which are round and oculi means eye) - round muscle around the eye - some fibers are just turning around your eyelid but some of them are present in your upper and lower eyelids
◦ functions: fibers in your eyelids are responsible for closing your eyes (when you go to sleep for example) but other fibers that make large circle around the eye are responsible for squeezing your eyes
*cranial nerve VII

Question 7

Nasalis

Answer 7

is a muscle bridging over your nose and it originates from your maxilla and moves towards the midline where it blends with the contralateral muscles so the left and right nasal muscls are forming a bridge over your nose
- function: when it contracts it compresses your nose to widen your nostrils (for ex. when you are running hard and are trying to maximize the intake of air into your respiratory system)

Question 8

Orbicularis oris

Answer 8

which is a round muscles which encircles around the oral cavity - this muscle has two halves (start from the maxilla and make a half turn around your mouth and then they get inserted to your mandible and then on their way they have massive attachment to the skin of your upper and lower lips - core of your lips is made by this muscle) -> largest muscle in the group (surrounds the oral fissure)
- function: softly close your mouth or purse your lips (kissing)

Question 9

Masseter

Answer 9

originates from zygomatic arch and it inserts on the lateral surface of ramus of the mandible - fivers are running vertically so it will elevate your mandible closing your jaw - can palpate the muscle when you clench your teeth - these are all innervated by mandibular division of cranial nerve V

Question 10

Temporalis

Answer 10

is a superficial muscle that is fan shape and it arises from the lateral surface of the temporal bone - the fibers are converging - inserts to the coronoid process of the mandible
- function: elevate your mandible

Question 11

Medial & Lateral Pterygoid

Answer 11

• two pterygoid muscles called lateral pterygoid and medial pterygoid - both of them originate from the pterygoid process of the sphenoid bone (main origin)
• medial pterygoid inserts on the inner or medial surface of the ramus of the mandible - fibers are almost vertical so they elevate your mandible as well - the fibers are also running obliquely so when it contracts it can move the mandible to the contralateral side (2 functions) -> moving the mandible from side to side (lateral one too)
• lateral pterygoid inserts on the condylar process of the mandible and some fibers will insert to the disc of your TMJ joint - running horizontally and it protrudes your mandible pulling it forward - so this muscles prepares the TMJ to be open as you have to bring the mandible forward a little to open it so it is not directly opening TMJ
• when your joint in unlocked and jaw is open your TMJ becomes quite unstable so when you are in a fight you want to keep your mouth closed as a punch to the mouth can dislocate your mandible and TMJ
• nerve supply is V3 of trigeminal nerve

Question 12

Muscles Inserting in Orbital Cavity

Answer 12

• within the orbital cavity other than eyeball and other nerves we have 7 muscles and six of which are dedicated to move your eyeball in different directions - those six are referred to as extra ocular muscles and then there is one called levator palpabrae superioris (lifts your upper eye lid - when you wake up in the morning)
  ◦ this one is partially innervated by some sympathetic fibers as well (fun fact)
• cranial nerve III (oculomotor) is mainly supplying these as it supplies 5 out of the 7 including LPS - partly innervated by this and sympathetic fibers coming from T1
• the most common sight for cancers in the lung is the apical part because of the apex of the lung is constantly ventilated with fresh air and only apical part is constantly active so even you are resting the apical part of your lung is still being ventilated by fresh air - cancer cells want oxygen to lung - apex of lung happens to be sitting to T1 and cancers of lung can infiltrate to that lung and one of the signs of cancer of the lung could be partial drooping of your upper eyelid because it invades T1 - the muscle which is lifting your upper eyelid is partly paralyzed, so it cannot keep your upper eyelid wide open (this is known as ptosis)
• cranial nerve IV (trochlear) and VI (abducens) also 2 extra oculor muscles - 3 cranial nerves are supplying these all together

Question 13

What are the two groups of muscles that does the pharynx have?

Answer 13

• pharynx is a muscular tube that is attached to your larynx
• pharynx has two groups of muscles - longitudinal muscles (can shorten the length of your pharynx and because the pharynx is attached to the larynx those same muscles can also elevate your larynx) and circular muscles

Question 14

Laryngeal elevators

Answer 14

longitudinal muscles of your of the pharynx that shorten the pharynx and elevate larynx
cranial nerve X

Question 15

Pharyngeal Constrictors

Answer 15

• pharyngeal constrictors - wrapping around pharynx and when they contract they make the lumen of your pharynx narrower
• shortening the pharynx and making it narrow, are two movements that you constantly do when you are swallowing something - part of swallowing mechanism
• pharyngeal muscles are innervated my cranial nerve X

Question 16

Palatine Muscles

Answer 16

• smaller group of muscles that are attached to your soft palate - these muscles can be coming from the base of the skull and they attach to your soft palate or they may start from the soft palate and go to your pharynx or tongue but regardless of their attachment we refer to them as palatine muscles and they are in charge of moving your soft palate when your are swallowing
• palatine muscles are also innervated by cranial nerve

Question 17

What can Tongue Muscles be divided into?

Answer 17

• can be divided into two groups: intrinsic and extrinsic muscles of the tongue
• intrinsic muscles have both attachments of origin and insertion inside the tongue - they could be running between the top and bottom of your tongue and between left or right sides of your tongue so they are entirely contains within the tongue region
• extrinsic muscles can start from bones like styloid process and ending to tongue or coming from hyoid bone ending to tongue or coming from mandible as it originates from there and fans out to tongue - muscle which has origin outside the tongue but insertion inside the tongue
• all of these muscles with exception of one are innervated by cranial nerve XII (hypoglossal)

Question 18

Intrinsic Muscles of Larynx

Answer 18

• nine pairs of muscles within larynx
• these short, small muscles are running between the cartilages of your larynx and they can move these cartilages relative to each other and by doing so they can change tension of vocal cords which is used in phonation
• innervated by cranial nerve X

Question 19

Sternocleidomastoid (SCM)

Answer 19

• sternocleidomastoid (SCM) is a massive muscle in neck region - muscle originates from the manubrium of the sternum and it also originates from your clavicle and then the two heads join together and they insert to the mastoid process of the temporal bone
• good example of how a muscle can move the insertion into the same plan as the origin
• when you contract that muscle it can do two things - bring the insertion closer to the origin like bending the neck and it can also bring the insertion mastoid process to the same anatomical plane as the origin of sternum - sitting in coronal plane in different levels
• bends the neck ipsilaterally (same side) and rotates your head or face to the contralateral side
• cranial nerve XI (accessory nerve)

Question 20

Supra-hyoid and infra-hyoid muscles

Answer 20

• just deep to your skin we have a group of superficial muscles in the neck which can be classified based on their position relative to the hyoid bone - one group are sitting above hyoid and one are sitting below therefore the names are supra-hyoid and infra-hyoid muscles
• supra-hyoid muscles are a group of muscles which are running between the styloid process of temporal bone and hyoid bone - sitting above the hyoid so when they contract they will elevate or lift the hyoid bone
• infra-hyoid bone will do the opposite are running between the sternum, your larynx and hyoid bone - so when they contract they will pull down the hyoid bone
• ansa cervacalis is the cervical loop of the neck which is a branch from the cervical plexus and it supplies the infrahyoid muscles whereas the suprahyoid muscles are innervated by cranial nerve V and VII

Question 21

Scalene Muscles

Answer 21

• scalene muscles and translation is ladder because their attachment is to transverse processes of the cervical vertebrae (except CI as per textbook)
• 3 of them on each side but we consider them as a group so the origin is transverse processes of cervical vertebrae and insertion either to rib I or II and you would expect them to elevate ribs I and II (they can also laterally flex the neck as per textbook)
• the nerve supply for the scalene muscles in the ventral rami of cervical spinal nerves