Myology

Question 1

Differentiate skeletal muscle tissue from skeletal muscles (which are organs) by listing the tissues present in any skeletal muscle.

Answer 1

• skeletal muscle tissue
• smooth muscle tissue
• c.t. proper
• epithelium
• nervous tissue (innervate)
• blood

Question 2

List the various functions that skeletal muscles perform in the body.

Answer 2

• Locomotion
• Posturing
• Respiration: increase in size of the thoracic cavity caused by contraction of the diaphragm and other thoracic muscles produce a partial vacuum
• Prehension: getting food and drink into the oral cavity
• Mastication: chewing it
• Deglutition: swallowing
• orifice closure: closing lips
• abdominal press: involves contraction of the diaphragm and the muscles forming the abdominal wall to increase the pressure within the abdominal and thoracic cavities (vomiting, defecation, urination, coughing, etc.)
• vocalization
• eye movements
• venous return: contraction of muscles assists movement of blood through the appendicular veins
• heat production: most skeletal muscles produce heat when they contract (shivering)

Question 3

Define the following as they relate to skeletal muscle structure: belly, tendon, aponeurosis, origin, insertion, epimysium, perimysium, endomysium, and fascicle.

Answer 3

belly: contractile part
tendon: fibrous connective tissue attachments
aponeurosis: broad sheet-like tendons (how some bellies attach)
origin: the attachment of muscle belly to the fixed part of the skeleton
insertion: attachment at the moveable end of a muscle belly
epimysium: skeletal muscles bellies are ensheathed in this fibrous connective tissue
endomysium: surrounds each muscle cell
perimysium: extend inward from the epimysium and segment muscle cells into groups
fascicle: cell groups

Question 4

what is a fleshy attachment?

Answer 4

tendons that are so short that the muscle belly appears to be directly anchored to bone.

Question 5

(Explain how each of the following relate to or interact with skeletal muscles.)

*know the diff. kinds of c.t. proper

Fasciae (know 2 kinds)

Answer 5

irregular collagenous connective tissue

bonds the skin to the underlying muscularture, binds muscles into groups, and serves as an avenue of penetration for vessels and nerves

1. superficial fascia (hypodermis, subcutaneous tissue) - directly under the skin; loose fibers
2. deep fascia - surrounds groups of muscles; denser irregular fibers

Question 6

(Explain how each of the following relate to or interact with skeletal muscles.)

*know the diff. kinds of c.t. proper

Retinacula

Answer 6

dense regular collagenous connective tissue

binds tendons into groups and hold them in certain locations

Question 7

(Explain how each of the following relate to or interact with skeletal muscles.)

*know the diff. kinds of c.t. proper

Bursae

Answer 7

synovial fluid sacs that are structurally similar to joint capsules (hv. fibrous outer layer and a synovial membrane lining)

they cushion (protect) the tendons and reduce sliding friction

Question 8

(Explain how each of the following relate to or interact with skeletal muscles.)

*know the diff. kinds of c.t. proper

Tendon Sheaths

Answer 8

bursae that completely surround tendons and from closed, fluid - filled encapsulations

Question 9

(Explain how each of the following relate to or interact with skeletal muscles.)

*know the diff. kinds of c.t. proper

Sesamoid Bones

Answer 9

accessory structures of skeletal muscles since they serve as bearing surfaces and protect tendons from frictional degeneration

ex) patella lifts the tendons up so you’re not rubbing on bone

Question 10

Name 3 muscles whose tendons usually contain sesamoid bones.

Answer 10

patella - largest sesamoid bones embedded in the tendons of the quadriceps femoris muscles

pair of sesamoid bones at the base of each thumb - embedded in the tendons of the flexor pollicis brevis muscles

pair as the base of each big toe - in the tendons of the flexor hallucis brevis muscles

Question 11

Differentiate myofiber, myofribil, myofilament, and myomere.

Answer 11

• myocytes (muscle cells) are also called myofibers
• myofibrils: specialized organelles; elongated cylinder
• myofilaments: rod-like contractile structures located in myofibrils

. myofilaments consist of thinner proteinaceous filaments composed of actin, troponin, myosin, and tropomyosin

• myomere: basic unit of skeletal muscle microstructure from Z line to Z line

Question 12

Schematically represent the arrangement of the thick and thin myofilaments in a myofibril and indicate what causes the A band, I band, H band, M line, and Z line.

Answer 12

A (anisotropic) band: dark cross bands produced by the thick myofilaments polarize visible light

(A dArk)

I (isotropic) band: don’t polarize visible light; extend from the edge of one stack of thick filaments (myosin) to the edge of the next stack of mysoin

(I light)

H band: the lighter central region of each A band consists of thick filaments (no overlap)

M line: dark transverse line (center of H band)

• protein overlap that connects myosin together

Z line: center of each I band crossed by a dark band = z line

• overlap that connects actin together
• formed by cross linking proteins that bind thin myofilaments together

Question 13

Which ultrastructural features get shorter during contraction?

Answer 13

I band, H band, and the distances between adjacent Z lines and M lines get narrower (everything but A band really)

Question 14

What is the action of a muscle cell?

Answer 14

the potential movement that contraction of the muscle evokes

Question 15

What three things happen when a muscle contracts?

Answer 15

1. no movement
2. the movement described by its stated action (you get what you want)
3. the opposite movement from its stated action (opposite action of what you want)

Question 16

what causes action?

Answer 16

1. contraction
2. elastic recoil
3. gravity

Question 17

Define and properly use the terms agonist, synergist, antagonist, and fixator.

Answer 17

1. Synergist - muscles which have the same action
2. Antagonist - muscles with opposing actions
3. Agonist - any muscle that is contracting; particular point of reference
4. Fixator - muscles which can contract to reduce or prevent one or more actions of a given muscle (while allowing other actions of the muscle to occur)

• antagonists to one or more actions of multi-actioned cells

Question 18

Explain why single - actioned muscles can be fixators but cannot have fixators.

Answer 18

A single actioned muscle can be a fixator by having its action be the antagonist to another action in the muscle. It can’t have a fixator because it has only one action so there are no other actions that need to be prevented.

Question 19

Explain why some muscles can have only one stated actions whereas others can have two or even more actions.

Answer 19

they only cross one joint so therefore they only have one action

they cross multiple joints

Question 20

Define motor unit and explain why muscles over which we have precise control are composed of small motor units.

Answer 20

Motor unit - single motor neuron and the groups of myofibers that it controls collectively

small motor units are used in muscles capable of precise movements because they are very quick and finite

Question 21

List the 7 major groups of skeletal muscles.

Answer 21

• muscles of the head
• neck
• back
• thorax
• abdomen
• superior limb
• inferior limb

Question 22

Divide the muscles of the head into 6 groups.

Answer 22

1. Muscles of the Face
   - m. orbicularis oculi
   - m. orbicularis oris
   - m. zygomaticus major
   - m. zygomaticus minor
   - m. levator labii superioris (cut)
   - m. depressor labii inferioris (cut)
   - m. mentalis
2. Muscles of the Ear
3. Muscles of the Eye
4. Muscles of Mastication
   - m. temporalis
   - m. masseter
   (strongest muscles of mastication)
   - lateral pterygoid m.
   - medial pterygoid m.

Question 23

What muscles are on the most superior part of the head? (occipital)

Answer 23

• Galea aponeurotica

- Frontal Belly of occipitofrontalis m.

Question 24

Divide the muscles of the neck into six groups.

Answer 24

Suprahyoid m.

Infrahyoid m.

Suboccipital m.

Pharyngeal m.

Laryngeal m.

other muscles of neck:

platysma (depress lower lip)
m. sternocleidomastoideus (turn head opposite side)

Question 25

What is the largest muscle of the thorax and what does it cover?

Answer 25

Largest: major pectoral muscle - most powerful flexor of shoulder joint Covers: minor pectoral muscle

Question 26

What muscle of the thorax joins the scapula to the ribs?

Answer 26

serratus anterior muscle

Question 27

What do intercostal muscles of the thorax do and give the name of the one that slants down and back from one rib to the next.

Answer 27

- they draw the ribs closer together | - internal intercostal muscle

Question 28

Schematically represent a transverse section through the anterior abdominal wall and label the bellies and aponeuroses of the muscles involved.

Answer 28

on pg. 249

Question 29

Differentiate the pelvic and urogenital diaphragms. (muscles of the abdomen) * ELC * BIT * UUU T

Answer 29

Pelvic Diaphragm: surround anus (between pubis, ischium, and rectum) - levator ani (4 parts) - coccygeus - external anal sphincter muscles Urogenital Diaphragm: surrounds vagina (between pubis and rectum in perineal region) - ischiocavernosus - bulbospongious - transversus perinei superficiales muscles (superficial group) - urethral sphincter - urethral compressor - urethrovaginal m. - transversus perinei profundus m. (deep group)

Question 30

# Define hypaxial and epaxial muscles. (muscles of the back)

Answer 30

Hypaxial muscles: those anterior to the transverse processes of the vertebrae (include those m. of the thorax and abdomen) Epaxial muscles: muscles of the posterior trunk which are positioned behind the transverse processes of the vertebrae

Question 31

Describe what the erector spinae muscles do, how many types of muscles it has, and what subdivision it belongs to.

Answer 31

1. They hold you up 2. 3 muscles 3. muscles of the back

Question 32

List what the trapezius muscle does as well as the latissimus dorsi muscle.

Answer 32

Trapezius m. - triangularly- shaped muscle that attaches to the spine of the scapula Latissimus dorsi m. - only one that attaches to the humerus - very unique, ppl. used to put it around hearts

Question 33

Divide the muscles of the superior limb into six regional groups and state the general actions of each group. (First 3)

Answer 33

1. Muscles of the Shoulder and Scapula: - moves humerus relative to scapula causing flexion, extension, rotation, adduction, abduction at the shoulder joint 2. Three Anterior Muscles of the Brachium - biceps brachii muscle: 1. strongest flexor of the elbow joint 2. strongest antebrachial supinator 3. flex the shoulder joint - brachialis muscle: 1. flex the elbow joint - brachioradialis muscle: 1. rotates the antebrachium, pronating a markedly supinated limb and supinating a markedly pronated one 3. Two Posterior Muscles of the Brachium - triceps brachii muscle: (has 3 heads) 1. extension of the elbow and shoulder joints - anconeus muscle: 1. also extends the elbow joint

Question 34

Divide the muscles of the head into six regional groups and state the general actions of each group. (Last 3)

Answer 34

Anterior Muscles of the antebrachium - 6 m. flex carpal and digital joints - 3. m rotate antebrachium (pronate/supinate) Posterior Muscles of the antebrachium - 9 m. extend carpal/digital joints Intrinsic Muscles of the hand - 3 Thenar muscles (thenar eminence) ACT ON THE THUMB - 4 hypothenar muscles (hypothenar eminence) ACT ON THE LITTLE FINGER - 4 intermediate muscles ACT ON THUMB AND OTHER DIGITS

Question 35

Divide the muscles of the inferior limb into nine regional groups and state the general actions of each group. (3 subtypes of Hip Muscles)

Answer 35

Anterior Muscles of the Hip - flex the hip joint - rotate the limb laterally Posterior/ Lateral Muscles of the Hip - extends hip joint - abduct and rotate the limb 6 Medial Muscles of the Hip - rotates the thigh laterally

Question 36

Divide the muscles of the inferior limb into nine regional groups and state the general actions of each group. (3 subtypes of Thigh Muscles)

Answer 36

Anterior Muscles of the Thigh - quadriceps femoris m. extends the knee joint - rectus femoris m. flex the hip joint (one of the heads of the quadriceps femoris muscles) Medial Muscles of the Thigh ``` Main Job: Adduct - gracilis muscle . adducts the inferior limb . medially rotates the inferior limb . flexes knee joint ``` - pectineus muscle (same thing as gracilis muscles) - 4 adductor muscles (adduct inferior limb) ``` Posterior Muscles of the Thigh Main Job: Flex the Knee joint - extend the hip joint - flex the knee joint - rotate the inferior limb ```

Question 37

Divide the muscles of the inferior limb into nine regional groups and state the general actions of each group. (3 subtypes of crus/pes)

Answer 37

Anterolateral Muscles of the Crus - 6 m. extend/flex the tarsal jts. (2 of them also extend the digital jts.) - evert the foot Posterior Muscles of the Crus - extend the tarsal joint - flex digital joint - flex genual joint Intrinsic Muscles of the pes 1. Special Muscle of Big Toe - flexors/ extensors - abductors/ adductors 2. Special Muscle of Little toe - abductor - flexor 3. Muscles common to several digits - digital extensors/flexors - digital abductors/adductors

Question 38

Name the three divisions of mesoderm on each side of the notochord and state which one gives rise to myoblasts.

Answer 38

Intermediate Mesoderm (mesomere): in some parts of the embryo forms the excretory units of the kidney Lateral Mesoderm (hypomere): splits into two layers (somatic and visceral) which contribute to the body wall and internal organs Paraxial Mesoderm (epimere): divided by transverse clefts into paired block- like masses called somites - somites give rise to sclerotome, dermatome, and myotome . Sclerotome: differentiates into c.t. proper, cartilage, and bone . Dermatome: forms dermis and subcutaneous tissue . Myotome: differentiate into myoblasts

Question 39

Explain what causes rigor mortis, cramps, and paralysis.

Answer 39

Rigor Mortis: occurs a few hours after death; the muscle tissue lacks the energy to relax and remains in a contracted state for a period of time until chemical degradation partially breaks it down Cramps: painful involuntary contractions that are related to alterations of the normal levels of certain electrolytes (calcium and potassium) Paralysis: loss of innervation - if a muscle loses innervation then most likely atrophy (loss in muscle mass) will occur