Muscle and Meat Structure

Dr. Hope stated that this was the hardest part of the entire class... ;)

What is “fresh” meat?

Meat that contains no added ingredients and is not frozen

• Some consumers additionally want good color and short display times

• This meat is quite perishable and has a very short shelf life even with refrigeration

What are red meat species?

Beef, swine, sheep, goat, and horse

What are white meat species?

Any meat from lighter-colored avian species

Locomotive muscle is (light/dark)

Light

• White muscle — short periods of activity

Structural muscle is (light/dark)

Dark

• Red muscle — long periods of sustained activity

(T/F) Poultry has only white meat

False

• Although it contains both red and white, poultry overall is simply considered “white” meat

In nutritional studies, what do “red meat” and “white meat” often serve as surrogate descriptors for?

Fat composition

• Red meat → more associated with saturated fat

• White meat → more associated with unsaturated fat

What two components is an animal converted to during slaughter?

Carcass and non-carcass components

Non-carcass components can be divided into two portions:

Edible and inedible portions—offal

What is offal?

Inedible portions of non-carcass meat

• Organs, skin, hides, blood, horns, head, etc

What are variety meats?

Edible offal

• Liver, hearts, kidneys… organs or tissues that are deemed wholesome and sold as food for human consumption

What are byproducts?

Inedible offal

• Feathers, poultry, blood, lungs… not sold at food for human consumption

Products derived from the carcass component and edible offal are referred to as ___

Meat

How is meat defined?

Consumable tissues from animals, Primarily:

• Skeletal muscle + associated tissues

• Edible offal (organs and non-skeletal tissues).

What are the 3 types of muscle?

1. Skeletal

2. Smooth

3. Cardiac

Where is the epimysium located?

A

Where is the perimysium located?

C

Where is the endomysium located?

D

Where is the sarcolemma located?

F

Where is the muscle bundle located?

B

Where is the muscle fiber located?

E

Where is the myofibril located?

G

Where is the sacromere located?

Q

Where is myofilament located?

R

What are the characteristics of skeletal muscle?

• Voluntary muscle, therefore under conscious control

• Skeletal muscle cells are defined by a cell membrane (sarcolemma)

• Multinucleated

• Contains a group of arranged contractile proteins

What color are I-bands? What else is the I-band known as?

Light in color, also called the “light band”

What color are A-bands? What else is the A-band known as?

Dark in color, also called the “dark band”

What causes the striations seen in skeletal muscle?

Alternating patterns of I and A-bands

What are Z-lines?

Also called Z-bands, bisectors of the I-bands

What is a sarcomere? What is it made up of?

The smallest contractile unit of muscle

• Spans from one Z-line to Z-line

• Contains 1 full A-band and 2 half I-bands

What two types of filaments do sarcomeres contain?

1. Thick filaments, composed of mostly myosin

2. Thin filaments, composed of mostly actin

Which filament is the most abundant (by mass)?

Myosin

Myosin and Actin are known as ____ proteins

Contractile

Troponin and Trypomyosin are known as ___ proteins

Regulatory

(T/F) Individuals filaments change length during muscle contraction.

False

• Thin filaments slide over thick filaments to shorten the sarcomere—there is no change in length to the filaments themselves

What is Titin?

The largest protein found in a sarcomere

• Part of its cytoskeleton

• Think Titan

What part of the myosin head allows it to participate in muscle contraction?

ATP-binding site

What are the two forms of actin?

G-actin and F-actin

What is G-actin?

individual, free actin protein molecules

• Aka, the singular bead

What is F-actin?

many G-actin molecules polymerized together into a long filament

• Aka, the string of beads

How many G-actin molecules are associated with one tropomyosin molecule?

7

What are thin filaments attached to?

The Z-line

What is the neuromuscular junction?

Where motor axons terminate, causing innervation of the skeletal muscle cells

• The place where the nervous system tells the muscle to contract

What is a motor unit?

The neuron and the fibers it supplies

• Neurons can innervate one to hundreds of muscle cells

What is the sarcoplasmic reticulum?

The specialized endoplasmic reticulum of a muscle cell

• Stores and releases calcium ions, which are necessary for contraction to take place

What structures does the sarcoplasmic reticulum contain?

A triad: one t-tibule and 2 terminal cisterna

What is 1 referring to?

The I-Band

• Its light!

What is 2 referring to?

The A-band

• Its dark!

What is 3 referring to?

The Z-line

What is structure A?

Terminal cisterna

What is structure B?

Sarcolemma

• Referring to the outer “shell”

What is structure C?

Transverse-tubule

• T-tubule

What is structure D?

• Longitudinal tubule

What is structure E?

Mitochondria

What are the four isoforms of myosin?

• Type I

  • Slow oxidative (SO)

• Type IIA

  • Fast oxidative (FO)

• Type IIX

  • Fast glycolytic (FG)

• Type IIB

  • Ditto, FG

What kind of contraction speed does Myosin’s Type I have? Type II? What are the relative sizes of their mitchondria?

• Type I — slow

  • Large

• Type II — fast

  • Small

    • Type IIA larger than IIB & IIX

What color are Myosin’s Type I and IIA? What kind of metabolism do they use?

Red, oxidative

What color are Myosin’s Type IIX and IIB? What kind of metabolism do they use?

White, glycolytic

What type of myosin fibers to cattle not have?

Type IIB

What are the characteristics of smooth muscle?

• Specialized for slow and sustained contractions

• Single centrally located nuclei

• Involuntary

• Ducts, digestive tract, veins, arteries, etc

What are the characteristics of cardiac muscle?

• Strong, continuous contractions

• Involuntary

• Appears striated due to the arrangement of contractile proteins

• Joined end to end via intercalated discs; anchors

• Heart

Which protein is the most abundant throughout the body?

Collagen

Myosin is the most abundant protein in ______ while Collagen is the most abundant protein in ____

Muscle, the body

What does Collagen influence in meat?

Quality, primarily tenderness

Are the crosslinks in collagen stronger or weaker in young animals?

Weaker

• Easily broken; explains why meat from younger animals is more tender

What allows an animal to pick up its head?

The ligamentum nuchae / nuchal ligament

As an muscle grows, there are primary and secondary perimysium levels. What does this impact?

Tenderness

Where is intramuscular fat deposited?

In the perimysium

Where is intermuscular fat deposited?

In the epimysium