The anatomy of a muscle - level 3 a & p revision

[Level 3 A & P] The Anatomy of a Muscle

There are 8 modules that you need to know for your Level 3 Anatomy and Physiology exam, The Anatomy of a Muscle makes up one of these 8 modules (musculoskeletal). In a typical exam of 40 multiple choice questions, you can expect to have between 3 and 5 questions about the structure and anatomy of the muscle.

To simplify the anatomy of a muscle, watch this 12-minute video and understand key terminology including:

  • Actin and Myosin
  • Sarcomere
  • Muscle Fibre
  • Endomysium
  • Fascicle
  • Perimysium
  • Muscle Belly
  • Epimysium
  • Tendon
  • Sliding Filament Theory

This video was taken from our full-length Live Revision Tutorial on YouTube. 

The Anatomy of A Muscle- Live Tutorial

The Anatomy of a Muscle – explained

The Actin and Myosin are the smallest parts, they interact to change the length of the muscle.

The Sarcomere is made up of the actin and the myosin.

A muscle fibre, or myofibril, is made up of multiple sarcomeres end on end

A Fascicle is a bundle of muscle fibres

A Muscle belly is a bundle of fascicles.

Essentially it is a Russian dolls approach… they all stack inside of each other, which is a smart way to get as many sarcomeres as possible in each muscle. This maximizes our ability to contract and change the length of the muscles,

This pulls on the tendon which joins muscle to bone

The tendon pulls on the bone.

The bone moves, creating an angle change in the joint = joint action.

Learn the Anatomy of a Muscle in 3 Steps:

Step 1 – The Accordion

We first need to step away from muscles in order to understand it a little better. Picture an Accordion Musical Instrument. It expands and contracts, folding onto itself. This is like a sarcomere.
A sarcomere expands and contracts as the myofilaments cross over each other.

Now imagine lots of these accordions all end on end… And they all contract and expand at the same time, like a band in unison.

One line of these accordions is like our muscle fibres, sometimes called myofibrils… which is made up of sarcomeres stacked end upon end.

When the muscle fibre is told to contract, all of the sarcomeres start to shorten in length, making a significant difference in length of the muscle. This is our muscle contracting.

Step 2 – The Sarcomere

The Sarcomere contains myofilaments, which are small contractile proteins.
Actin is the Thin myofilament and
Myosin is the Fat myofilament with the golf club heads.

These two myofilaments connect at cross bridges and pull together. This is a concentric contraction, with the muscle getting shorter.

They can also lengthen under contraction which is an eccentric contraction.

Step 3 – The big picture – the sliding filament theory

The video above will give clarity to all of these three steps and help you understand the muscle structure in relation to muscle contractions 🙂

To check your understanding, download 48 free mock questions for level 3 A & P here:

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