Lab 8 Vertebrate Anatomy Muscle

Attachments

  • Tendons: muscle to bone

  • Ligaments: bone to bone

Muscles consist of bundles of bundles

  • Muscle: bundles of fascicles (covered by a layer of connective tissue called epimysium)

  • Fascicle: bundles of muscle fibers (covered by a layer of connective tissue called perimysium)

  • Muscle fiber: bundles of myofibrils (covered by a layer of connective tissue called endomysium)

    • skeletal (striated) muscle fibers consist of myofibrils (which are rows of sarcomeres)

      • this is not the case in smooth muscle, which has thin and thick filaments that don’t arrange into sarcomeres

  • Myofibril: bundles of myofilaments; sarcomere level

  • Myofilament (actin and myosin): interact to generate contraction of sarcomere

Muscle: Basic Histology

  • Sarcomeres: the contractile units of a muscle bundle

  • Sarcomere boundaries are Z disks (aka Z-lines) that hold thin filaments in position

    • in other words, a sarcomere is a region between 2 adjacent z-lines, containing thin actin filaments and thick myosin filaments

    • as a muscle is contracting, you’re bringing the two adjacent z-lines together (Z-disks are pulled together to shorten muscle and contract)

  • The sarcomere’s M-line (middle) holds thick filaments in position

  • Overlapping thick and thin filaments make up the A-band (dark) with the M-line in the center

  • The area of the sarcomeres that only consist of thin filaments makes up the I-band (light) with the Z line in the middle

Muscle Actions (antagonist pairing)

  • Extensors vs Flexors:

    • increase vs decrease joint angle

    • ex: quadriceps extend the knee, while hamstrings flex it

  • Abductors vs Adductors:

    • away from vs toward the body’s midline

    • ex: pectoralis major adducts the arm

  • Retractors vs Protractors:

    • move back vs move forward

  • Supinators vs Pronators:

    • palm/sole anterior vs palm/sole posterior

Muscle Orientation

  • Origin:

    • fixed end of the muscle

    • sometimes difficult to determine (i.e., back muscles)

    • the end closest to the midline of the body

    • Limbs: proximal, trunk: Medial

  • Insertion:

    • portion that causes motion when muscle contracts

    • the end that is furthest from the midline of the body

    • Limbs: distal, trunk: Lateral

Anatomical Orientation

  • Superior vs Inferior

    • closer to the head/upper part of the body vs closer to the feet/away from head

  • Medial vs Lateral

    • toward the midline vs away from the midline of the body

  • Proximal vs Distal

    • toward the origin or trunk of the body vs away from the origin or trunk

  • Superficial vs Deep

    • closer to the body's surface vs away from the body's surface (closer to the body’s interior)

  • Anterior = Ventral vs Posterior = Dorsal

    • the front of the body or structure vs the back

  • Cranial vs Caudal

    • towards the head or skull vs towards the tail end of the body

  • Frontal (coronal) Plane

    • divides the body into a front half and a back half

  • Transverse Plane

    • divides the body into an upper half and lower half

  • Sagittal Plane

    • dividing the body into a left section and a right section

Dorsal/Lateral Aspect Muscles

  • The trapezius is divided into portions name for their different origins:

    • Clavotrapezius

    • Acromiotrapezius

    • Spinotrapezius

  • The trapezius, spinodeltoideus, bicep brachii, latissimus dorsi cross the shoulder joint and move the arm

  • External and internal obliques contain the abdomen

  • Tensor fasciae latae, gluteus maximus, semitendinosus, and biceps femoris cross the hip joint to move the leg

  • Gastrocnemius is the calf muscle that moves the foot

Ventral Aspect Muscles

  • Sternohyoid muscle is used for swallowing and speaking

    • hyoid bone attached to multiple muscles and important for swallowing and speaking

  • Pectoralis major and pectoralis minor are parts of the same muscle with different origins that cross the shoulder joint

  • Linea alba (white line) is connective tissue joining the right and left obliques

    • surrounded by rectus abdominus (aka abs) and provides strength

Notes from Class:

  • Quadriceps (particularly rectus femoris) – flex the hip and extend the knee

  • Hamstrings – extend the hip and flex the knee

  • Retractors vs protractors – move back and forward. Bring shoulders forward – protraction (and a little of internal rotation). Push them back – retraction (and a little of external rotation).

  • Cannot have an origin and insertion on the same bone, but must have on the same muscle.

  • Gastrocnemius is the external calf part and Soleus is the internal calf part.

  • Sphincters in butt are circular muscles.

  • Biceps femoris is a big hamstring muscle

    • semitendinosus helps the biceps femoris

  • Rectus femoris is a big quad muscle (antagonist to Biceps femoris)

  • Deltoid tuberosity: insertion of the deltoid found on the humerus.

  • Deltoid origin is the scapula.

  • Myostatin: the protein that controls our bodies from making too much muscle.

  • Pectoralis minor is deep to the Pectoralis major.

  • Origin of biceps: scapula

  • Insertion of biceps: radial tuberosity of radius bone

  • Origin of gastrocnemius: femur head

  • Insertion of gastrocnemius: Achilles tendon

  • Hamstring group: semitendinosus and biceps femoris

  • Isotonic: keeps the tone the same, muscles shorten (length of muscle changes and constant tension- picking up a weight)

  • Isometric: tension changes, but there is no change in the muscles’ length (clenching fist or closing eyes tightly)