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Flashcards in Myology Deck (39):

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

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


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

- 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)


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

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


what is a fleshy attachment?

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


(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)

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


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

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


dense regular collagenous connective tissue

binds tendons into groups and hold them in certain locations


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

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


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


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

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

Tendon Sheaths

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


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

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

Sesamoid Bones

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


Name 3 muscles whose tendons usually contain sesamoid bones.

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


Differentiate myofiber, myofribil, myofilament, and myomere.

- 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


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.

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


Which ultrastructural features get shorter during contraction?

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


What is the action of a muscle cell?

the potential movement that contraction of the muscle evokes


What three things happen when a muscle contracts?

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)


what causes action?

1. contraction
2. elastic recoil
3. gravity


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

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


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

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.


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

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

they cross multiple joints


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

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


List the 7 major groups of skeletal muscles.

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


Divide the muscles of the head into 6 groups.

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.


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

- Galea aponeurotica
- Frontal Belly of occipitofrontalis m.


Divide the muscles of the neck into six groups.

Suprahyoid m.

Infrahyoid m.

Suboccipital m.

Pharyngeal m.

Laryngeal m.

other muscles of neck:

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


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

Largest: major pectoral muscle

- most powerful flexor of shoulder joint

Covers: minor pectoral muscle


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

serratus anterior muscle


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.

- they draw the ribs closer together

- internal intercostal muscle


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

on pg. 249


Differentiate the pelvic and urogenital diaphragms.

(muscles of the abdomen)




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)


Define hypaxial and epaxial muscles.

(muscles of the back)

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


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

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


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

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


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

(First 3)

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


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

(Last 3)

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)


- 4 hypothenar muscles (hypothenar eminence)


- 4 intermediate muscles



Divide the muscles of the inferior limb into nine regional groups and state the general actions of each group.

(3 subtypes of Hip Muscles)

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


Divide the muscles of the inferior limb into nine regional groups and state the general actions of each group.

(3 subtypes of Thigh Muscles)

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


Divide the muscles of the inferior limb into nine regional groups and state the general actions of each group.

(3 subtypes of crus/pes)

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


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

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


Explain what causes rigor mortis, cramps, and paralysis.

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