Week 3 Muscles (Foot and Leg Region) Anatomy Workbook PDF

**Week 3: Muscles (focus on the foot and leg region)** **1. Causes of motion at joints** Before we look specifically at muscles, it is important for you to consider what causes motion at joints. This might sound straightforward, but it can be confusing when you start to analyse movement. Movement...

**Week 3: Muscles (focus on the foot and leg region)** **1. Causes of motion at joints** Before we look specifically at muscles, it is important for you to consider what causes motion at joints. This might sound straightforward, but it can be confusing when you start to analyse movement. Movement of the body at joints can be caused by: i\) **Muscle contraction** **2. Structure of muscles/Types of muscle work** Muscles are responsible for most body movement. When considering functional and structural characteristics, 3 main types are identified: - **The Human Body has over 600 skeletal muscles** - **These generally, work in pairs / groups (synergistically i.e. working together or in antagonistic pairs)** - **Origins = normally attached to bone via a tendon and often remains stationary.** - **Insertions = normally attached to bone via a tendon and often moves.** A skeletal muscle is made up of: **Contractile elements - Muscle fibres capable of generating force/muscle tension which provides adaptability in relation to muscle length.** **Non contractile elements - Connective tissue which distributes tension and force within the muscle and from muscle fibre to skeletal system. It also provides structural support and acts as a conduit for muscle fibres, nerves, and blood vessels.** **The microscopic structure will be introduced in the Physiology lectures, and you also need to read around this area for yourself in textbooks and using online apps.** Muscles are under the control of the nervous system and the basic element you will come across is the **motor unit.** - **Exercise 1** Read about motor units in a physiology textbook or try this video: [Muscles, Part 2 - Organismal Level: Crash Course Anatomy & Physiology \#22 (youtube.com)](https://www.youtube.com/watch?v=I80Xx7pA9hQ&t=90s)) Make short notes on the following: - What is a motor unit? - What type of motor neurone innervates a motor unit? - What is the "*all or none*" law? - Motor units can vary in size -- why is this important? - Which motor units are most excitable? - What is the '*size principle*'? - Explain recruitment. **Architecture of muscles** - **Wide variation in size, shape, and complexity** - **Fibres in muscles vary in number, size and direction relative to line of pull of the tendon attaching them to bone.** - **Fasciculation differs (fascicle = groups of muscle fibres held together by perimysium)** - **Fine - eye/hand muscles (small number of small fibres in each fasciculus)** - **Coarse -- large anti-gravity muscles (larger numbers of larger muscle fibres in one fasciculus) e.g. gluteus maximus** **\ ** **Common arrangements of muscles or muscle forms** - **Strap (parallel) and fusiform -- tendon at each end and fibres arranged in parallel (can be short or long)** - **Unipennate** - **Bipennate** - **Both of the above have a central tendon -- short muscle fibres are inserted into it. Fibre direction is different to line of pull of muscle.** - **Multipennate/triangular/convergent -- mixed characteristics** - **Muscular sheets** - **Circular** **Have a look Soames & Palastanga -- part 1 Components of the MSK System to see images of the different shapes of skeletal muscles.** The force a muscle can generate depends on its mass of contractile tissue i.e. the number and size of muscle fibres it contains. The cross-sectional area of a muscle gives an indication of its power: the bigger it is the larger amount of force it can generate. **Types of muscle activity (contraction)** - **Commonly used terms** - **Isometric (static) -- muscle is active but no visible movement of bones (internal tension = external force = balance)** - **Isokinetic -- muscle produces movement and movement appears to occur at constant velocity (force produced may vary as muscle length changes)** - **Isotonic -- movement of one or more bones to which muscle is attached. Dynamic - muscle may become longer or shorter (velocity and force may vary during activity)** **Isotonic muscle activity** - **Concentric -- internal force generated greater than external force = shortening** - **Eccentric -- active muscle generates less force than external load = lengthening** - **Exercise 2** **Think of some examples of isometric, concentric and eccentric muscle activities and note them down below:** **\ ** **3. Muscles of the foot and leg region** **Have a look at this video:** [Muscles of the Leg - 3D Models, Video Tutorials & Notes \| AnatomyZone](https://anatomyzone.com/lower-limb/leg/muscles-of-the-leg/) (make sure you click "next" to see part 2 also). There are 2 main groups of muscles that we need to consider in this area: 1\. The **extrinsic** muscles in the leg (i.e. between the knee and the ankle) -- many of these do cause movements of the foot in relation to the leg, as well as movements of the toes. Before you go on to think about the muscles in this area, it will be useful for you to get an idea of the arrangement of the tibia and fibula - as these are the bones that the majority of the muscles attach to. 2\. The **intrinsic** muscles in the foot (i.e. the small muscles found in the foot itself). - **Exercise 3** Look at the diagram below. This is a transverse section of the right leg from above showing the bones, fascia and interosseous membrane. Have a go at labelling the bony landmarks and the deep and connective tissue (superficial fascia): Tibia Fibula Connective Tissue/Fascia IB = IB = IM = AB = PB = MB = MC = You should particularly note the **borders** of the bones shown in the diagram as these are where muscles attach. The interosseous borders are joined by the tough **interosseous** **membrane** - muscles attach to this too. The diagram also shows the layers of **fascia**. **Fascia (fasciae -- plural)** -- connective tissue layer/wrapping that surrounds and supports organs and other structures such as muscles. Learn more about fascia on the following link: [Fascia: anatomy, structure and function. \| Kenhub](https://www.kenhub.com/en/library/anatomy/fascia). +-----------------------------------------------------------------------+ | **? Week 3:** **Question 1 Fascia** | +-----------------------------------------------------------------------+ | 1\. Where is superficial fascia in relation to the skin? | | | | 2\. What type of tissue is superficial fascia? | | | | 3\. Give one function of this tissue: | | | | 4\. What is deep fascia made up of? | | | | 5\. Deep fascia is particularly well developed in the upper and | | lower limbs where it forms a \_ \_ \_ \_ \_ \_ around many of the | | muscles. | +-----------------------------------------------------------------------+ The deep fascia in the leg is dense, tough, and bluish white. It could be described as a tube or stocking. Above, it is continuous with the deep fascia of the thigh and below with the **retinaculae** around the ankle. Where it contacts bone, it blends with the periosteum. The leg is divided into **compartments** by the deep fascia, the interosseous membrane and structures called intermuscular septa - look at the diagram on the next page. As you can see, the compartments are: Anterior Lateral Posterior The posterior compartment is further divided into deep and superficial compartments by the deep transverse fascia. There are also expansions from the deep fascia that surround individual muscles. All of these sheets of fascia are joined and act as a connective tissue skeleton that both divides and supports the muscles. Each compartment contains a number of muscles that are sometimes known as the **crural** muscles, and these are named for the compartment they are in: - **Exercise 4** Look **Soames & Palastanga -- part 3 Leg/Calf** and then list the muscles found in each compartment below: **Anterior crural muscles:** **Lateral crural muscles:** **Posterior crural muscles:** Superficial compartment - Deep compartment -- It is important for you to know where the muscles are in relation to one another i.e. which are deep, which are superficial and whether this changes at all throughout their length. Look at the diagram on the next page to see how the muscles fit into their respective compartments (some of the muscles mentioned above are not on the diagram, this is because of the level at which the cross section is taken - **try to work out which ones are missing and why**). As well as knowing where the muscles are relative to each other it is also important for you to know the positions of the **tendons** at the ankle joint. As some of the muscle bellies are deep and therefore impossible to palpate - you need to know how to identify their tendons. This information will help you to know whether the muscles are working normally or not. *If you are able to identify these tendons (as well as the muscle bellies where possible) by palpation, you will be able to use this skill when examining patients. This will give you an indication of the position of any injury and so their possible problems and will help you to focus your treatment effectively in the correct area.* You should now think back to the **movements** of the ankle joint and foot that you learned earlier. The question below and on the next page deals with these: +-----------------------------------------------------------------------+ | **? Week 3:** **Question 2 Movements and muscles - ankle and foot** | +-----------------------------------------------------------------------+ | In the spaces provided overleaf you should note down the movements of | | the ankle, foot and toes and then list the muscles responsible for | | those movements (do not include any intrinsic foot muscles): | | | | 1. **Movements of the ankle joint:** | | | | **Movement Muscles** | | | | i) | | | | ii) | | | | **2. Movements of the subtalar joint:** | | | | **Movement Muscles** | | | | i) | | | | ii) | | | | **3. Movements of the toes including the hallux:** | | | | **Movement Muscles** | | | | i) | | | | ii) | +-----------------------------------------------------------------------+ - **Exercise 5** *Go back to the diagram of the muscles within their respective compartments and see where they are in relation to the movements they produce e.g. are the flexors of the toes in front of the leg or behind?* By the time you have got to this stage, you should have an overview in your mind of the muscles in this area, their names, and the movements they produce. They all work together to **stabilise** the ankle, stabilising the leg on the foot. They are also very important in balance and adapting the foot to rough or uneven ground. Many of the muscles help to support the arches of the foot. - **Exercise 6** *Get together with another student or find someone else who is a willing volunteer. Ask them to stand on one leg and look at what happens in the tendons around the ankle joint.* *What happens if you **gently** push them off balance?* **4. Muscles that plantarflex the ankle joint** Gastrocnemius and soleus are the main muscles you need to concentrate on here but, as you know, the other muscles involved in this movement are: *Plantaris* is what is known as a vestigial muscle (*vestigial* = atrophied or functionless from the process of evolution). It is sometimes referred to as a \"spare part\" because its tendon may be used for tendon transplants. Read about **gastrocnemius** in **Soames & Palastanga -- part 3 Ankle** and then use the following SAQ to help you write notes on it: +-----------------------------------------------------------------------+ | **? Week 3:** **Question 3 Gastrocnemius** | +-----------------------------------------------------------------------+ | 1\. Where is the bulk of gastrocnemius situated? | | | | 2\. What is the *triceps surae*? | | | | 3\. Where do the 2 heads of gastrocnemius arise? | | | | 4\. What separates each head of gastrocnemius from the knee joint | | capsule? | | | | 5\. What happens to the heads of gastrocnemius as they pass down the | | leg? | | | | 6\. Where does it eventually attach? | | | | 7\. What is the nerve supply of gastrocnemius? | +-----------------------------------------------------------------------+ | **? Week 3:** **Question 3 continued** | +-----------------------------------------------------------------------+ | 8\. What are the actions of this muscle? | | | | 9\. What are its functions? | +-----------------------------------------------------------------------+ - **Exercise 7** *Use the same headings to make notes on **soleus** below:* +-----------------------------------------------------------------------+ | **? Week 3:** **Question 4 The tendocalcaneus** | +-----------------------------------------------------------------------+ | The tendocalcaneus is the thickest and strongest tendon in the body. | | | | 1\. Name the muscles that attach via this tendon? | | | | 2\. Where does it attach? | | | | 3\. The calf muscles exert their force on the posterior part of the | | foot during which type of activities? | | | | 4\. How much strain is the tendon able to withstand? | | | | 5\. What happens to the fibres of the tendocalcaneus as they pass | | downwards? | | | | 6\. Why is this significant? | +-----------------------------------------------------------------------+ **5. Dorsiflexors of the ankle joint** You are already familiar with the names of the muscles involved here - but the major one is tibialis anterior \[TA\]. (The other 3 muscles: extensor digitorum longus \[EDL\], extensor hallucis longus \[EHL\] and peroneus tertius \[PT\] are covered later, as dorsiflexion is not their primary function). - **Exercise 8** *Tibialis anterior is a very easy muscle to find - if you follow the anterior border of the tibia about one third of the way down and slide slightly laterally, you can feel a big bulk of muscle under your fingers when you dorsiflex - this is TA. At the front of the ankle, it is the biggest tendon - slightly to the medial side.* *Have a go at finding it on yourself and then on someone else.* *While you\'ve got a model available - have a go at finding gastrocnemius and soleus too. This is all good practice - ask them to tell you if your palpation is **comfortable** or not.* Make notes on TA following the headings below: 1\. Shape of the muscle - 2\. Position of the muscle - 3\. Proximal attachment - 4\. Distal attachment (and how it gets there) - 5\. Nerve supply - 6\. Action/functions - **6. Invertors of the foot** (note - \"of the foot\", inversion and eversion occur at joints between the tarsal bones **NOT** at the ankle joint) You have just made notes on TA. The other invertor is **tibialis posterior**. You should check back to see which compartment of the leg this muscle is in, then fill in the table below: ---------------------------------------- ------------------------ ------------------- **Name of muscle:** Tibialis Posterior **Attachments:** **Actions/functions:** **Nerve supply:** ---------------------------------------- ------------------------ ------------------- Before moving on, just make sure you know which part of this muscle you can palpate and note it down: **7. Evertors of the foot** These are: Peroneus longus, Peroneus brevis and Peroneus tertius. The first 2 muscles, which are found in the lateral compartment of the leg, need to be covered in detail, but the third one, found in the anterior compartment, you only need in outline. The most complex aspect of peroneus longus is what happens to its tendon. It changes direction a number of times before it reaches the distal attachment. Read about it and then try the SAQ on the next page: +-----------------------------------------------------------------------+ | **? Week 3:** **Question 5 Peroneus longus** | +-----------------------------------------------------------------------+ | 1\. Peroneus longus is situated on which side of the leg? | | | | 2\. Where are its proximal attachments? | | | | 3\. How far above the lateral malleolus does the tendon form? | | | | 4\. It shares a synovial sheath with what other structure? | | | | 5\. What route does the tendon take? | | | | 6\. Where does it attach at its distal end? | | | | 7\. It is supplied by the \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ | | \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ nerve, L5. S1 | | | | 8\. What are its action/functions? | +-----------------------------------------------------------------------+ - **Exercise 9** *Make sure that you can find peroneus longus and brevis on yourself and then on someone else. Make the muscles work by everting the foot. When you try this on a model (or friend, helpful member of the family etc!!) give them some resistance to the movement i.e. by placing your hand on the outside of the foot asking them to push against it.* *Make a note of how to palpate these muscles*. You should now make your own notes on peroneus brevis and tertius (the latter in outline only) - use extra paper if necessary. See diagrams in **Soames & Palastanga -- part 3 Leg/Calf**. **\ ** **8. Flexion and extension of the toes** These movements are produced partly by the extrinsic muscles included in the list earlier and partly by the small intrinsic muscles which are found in the foot itself. At this time, you only need to consider the extrinsic muscles in outline. Read **Soames & Palastanga -- part 3 Foot** and look at the accompanying diagrams then make notes on these muscles: - Flexor Digitorum Longus - Flexor Hallucis Longus - Extensor Hallucis Longus - Extensor Digitorum Longus - **Exercise 9** *Make a note below of how to palpate the previous four muscles:* **9. The intrinsic muscles of the foot** It is important for you to have some information on the small muscles in the foot. Look at the text and accompanying diagrams in an anatomy textbook of your choice. - **Exercise 10** *Use the following table pick out the muscles of the foot that produce each of the movements mentioned:* +-----------------------------------------------------------------------+ | **Intrinsic muscles that extend the toes** | +-----------------------------------------------------------------------+ | i) | | | | ii) | | | | iii) | +-----------------------------------------------------------------------+ | **Intrinsic muscles that flex the toes** | +-----------------------------------------------------------------------+ | i) | | | | ii) | | | | iii) | | | | iv) | | | | v) | | | | vi) | +-----------------------------------------------------------------------+ +-----------------------------------------------------------------------+ | **Intrinsic muscles that abduct the toes** | +-----------------------------------------------------------------------+ | i) | | | | ii) | | | | iii) | +-----------------------------------------------------------------------+ | **Intrinsic muscles that adduct the toes** | +-----------------------------------------------------------------------+ | i) | | | | ii) | +-----------------------------------------------------------------------+ By now you should be familiar with names of the muscles which help to produce the toe movements. A handy hint to help you remember which interossei produce which movement are the following words - **PAD**s and **DAB**s: i.e. **[P]**lantar interossei **[AD]**duct the toe**[s.]** **[D]**orsal interossei **[AB]**duct the toe**[s.]** The intrinsic muscles are also sometimes described in 4 layers -- the muscles in each layer are named below: **1^st^ layer -- most superficial:** Abductor hallucis Flexor digitorum brevis Abductor digiti minimi **2^nd^ layer:** The lumbricals Flexor digitorum accessorius **3^rd^ layer:** Flexor hallucis brevis Adductor hallucis Flexor digiti minimi brevis **4^th^ layer -- the deepest:** Plantar interossei You should make VERY BRIEF notes on attachments of the above muscles. The dorsal interossei are not included in these layers so you also need to be sure you are aware of their positions and attachments. There is one more muscle you need to find out about - this is extensor digitorum brevis - the only muscle on the dorsum of the foot. Make some notes about it (very brief ones!). Returning to the structure and function of the foot - the arches (remember the 2 longitudinal and one transverse) formed by the bones show a visible **concavity** in the sole of the foot. - **Exercise 11** *Have a look at your own foot - look at the arches.* *Try to compare them with some other people\'s - is it flatter, higher, the same? What happens to the arch when you put your weight through the foot?* *What happens when you extend your toes?* *It is important that you become familiar with a range of \"normal\" feet. Then when you start to examine patients/clients you will be in a better position to recognise changes and differences.* Remember that you can look in a range of textbooks and at online resources for diagrams and descriptions of all of the structures mentioned in this section of the workbook. **10. Connective Tissue Structures** **Plantar Aponeurosis** This is a layer of fascia in the sole of the foot -- the thickest fascia in the body (up to 80 layers thick). It is very important in maintaining the longitudinal arches of the foot. It also provides muscle attachment and supports, separates and protects other structures in the foot such as tendons, nerves and blood vessels. Read about it and answer the following questions: +-----------------------------------------------------------------------+ | **? Week 3:** **Question 6 Plantar aponeurosis** | +=======================================================================+ | 1\. What shape is this structure? | | | | 2\. Where does it attach posteriorly? | | | | 3\. As it passes anteriorly, how many slips/sections does it divide | | into? | | | | 4\. What happens to these slips and where do they attach? | +-----------------------------------------------------------------------+ **\ ** **Retinaculae** These are thickenings of the deep fascia of the leg. Read about them and fill in the table below: - **Exercise 12** *Make notes using the following table:* **Name of retinaculum** **Attachments** **Structures running beneath retinaculum** ------------------------- ----------------- -------------------------------------------- The purpose of the retinaculae around the ankle joint is: