Muscular System
Questions Received:
How many facial muscles does it take when you laugh or smile and how many calories do you burn?
Identify and locate at least 10 major muscles of the body (include diagram).
Responses:
How many facial muscles does it take when you laugh or smile and how many calories do you burn?
23rd March 1999
Five pairs of facial muscles have a particular role in laughing and smiling, as shown in the table below. However, it is likely that most of the 53 named facial muscles play at least some part in these expressions, particularly when the expression is exaggerated, and other groups of muscles such as the muscles of mastication and respiration. The neck muscles will also be involved. So it is rather arbitrary to emphasise just 5 pairs of laughing/smiling muscles. Furthermore, there are some facial muscles that have a complicated arrangement, and not everyone agrees on whether they should be labelled collectively or individually. Also, there are some muscles that are present only in some people (eg: transversus nuchae, malaris), which further complicates the answer to this question.
As to how many calories will be used during laughing and smiling - we are unable to give a precise answer. The published figures relate to more prolonged activities such as walking and running, etc. However, bearing in mind that the mass of the facial muscles is small and that smiling and laughing are rarely sustained for long periods, it is clear that calorie use will be correspondingly small.
The muscles of facial expression lie just beneath the skin in the face, neck, and scalp regions. Not all of them have an attachment to underlying bone - they act predominantly on the skin. The muscles are arranged around the eyelids, lips, nose, and external ear, and also within the cheek and scalp. One muscle - platysma - extends from the face down through the neck region to the upper chest. All the muscles in the group are supplied by the facial nerve (cranial nerve 7).
| Muscle | Action or Expression |
| Occipitofrontalis (4 muscle bellies) | Retracts scalp, raises eyebrows |
| Temporoparietalis (2) | Stabilises scalp |
| Auricularis Anterior, Superior, and Posterior (6 bellies) | Move external ears |
| Orbicularis Oculi (2) | Closes eye |
| Levator Palpebrae Superioris (2) | Lifts upper eyelid |
| Depressor Supercilii (2) | Lowers eyebrow |
| Corrugator Supercilii (2) | Frowning |
| Procerus (2) | Frowning and concentration |
| Nasalis (2) | Flares nostrils |
| Depressor Septi (2) | Flares nostrils |
| Levator Labii Superioris Alaeque Nasi (2) | Raises upper lip, dilates nostrils |
| Levator Labii Superioris (2) | Elevates upper lip |
| Zygomaticus Minor (2) | Smiling, smugness, disdain |
| Levator Anguli Oris (2) | Smiling |
| Zygomaticus Major (2) | Laughing |
| Risorius (2) | Laughing and other expressions |
| Mentalis (2) | Lifts skin over chin |
| Depressor Labii Inferioris (2) | Irony, sorrow, melancholy, doubt |
| Depressor Anguli Oris (2) | Sadness |
| Buccinator (2) | Compresses cheek against teeth |
| Orbicularis Oris (1) | Closes mouth |
| Incisivus Labii Superioris (2) | Movements of upper lip |
| Incisivus Labii Inferioris (2) | Movements of lower lip |
| Platysma (2) | Opens jaw and mouth, wrinkles skin over chest and neck |
< Diagram showing some of the muscles of facial expression (based on a drawing by Hans Arkeveld)
What is the job of the muscular system?
12th April 1999
Muscle cells are specialised to contract and do work. So they can actively bring about change. There are three different types of muscle tissue known as smooth, cardiac, and skeletal muscle. The muscles we tend to talk about are the ones that help us to move around - the skeletal muscles. They attach to the skeleton and produce movement at joints. We can control most skeletal muscles as we wish, so we say they are under voluntary control. Cardiac muscle is found only in the heart - it is specialised to beat rhythmically from the time the heart first becomes functional, just three weeks after conception, to the time we die. We do not have voluntary control of the heart, so we consider cardiac muscle to be involuntary. Smooth muscle is also involuntary, and is found in the walls of the intestines, blood vessels, and in many other locations. It plays an important part in digestive movements, the control of blood pressure and numerous other activities that generally occur without us being aware of them. In doing work, muscle cells are metabolically very active and produce heat that helps us to maintain our normal body temperature.
Identify and locate at least 10 major muscles of the body (include diagram).
20th April 1999
<
Skeletal Muscles of the Body, Anterior View
Key:
1 = Biceps Brachii
2 = Pectoralis Major
3 = Rectus Abdominis
4 = Sartorius
<
Skeletal Muscles, Posterior View
Key:
5 = latissimus dorsi
6 = trapezius
7 = gluteus maximus
< Skeletal Muscles From The Side
Key:
8 = serratus anterior
9 = triceps
10 = gastrocnemius
Diagrams adapted from: Wirhed, R. (1991) Athletic ability and the anatomy of motion. London: Wolfe Publications.
Does it take more muscles to laugh or to frown?
9th June 1999
We usually say that frowning requires more muscles than laughing. That is probably correct if we are comparing like with like, say a slight smile with a slight frown, or a medium laugh with a medium frown.
However, we should be careful about several things here. Firstly, when we say ‘more muscles’, do we mean a greater number of muscles, or a greater amount of muscle? The muscles of facial expression differ in size and bulk, so that could influence the answer. We also have to remember that the naming of muscles can be somewhat arbitrary, and sometimes for historical reasons tiny bundles of muscle fibres have been given their own name while other bundles are considered to be part of a larger set which is named collectively. Secondly, as noted in our previous answer (see above) about the muscles used in laughing and smiling, it is likely that most of the 53 named facial muscles play at least some part in all these expressions, particularly when the expression is exaggerated - not to mention other groups of muscles such as the muscles of mastication and respiration. Thirdly, when we laugh happily we often generate quite a bit of noise, and this reflects muscular activity in the larynx, chest and abdomen. On the other hand frowning tends to be a relatively quiet affair, so it could be that a big laugh requires more muscles than a big frown.
One way to check would be to compare oxygen use during laughing and frowning. While we wait for those results, I think it is probably best in the interests of energy conservation to laugh more than frown.
27th November 1999
For an overview of the muscles of the nose, consult a good anatomical textbook such as Gray’s Anatomy (1989). The four main muscles are:
Procerus - extends from the bridge of the nose to the skin between the eyebrows; action: pulls down the medial end of the eyebrow, as in frowning and protecting the eyes from glare
Nasalis - this has two parts across the side of the nose: a transverse part and an alar part; actions: modification of nasal aperture
Depressor Septi - extending vertically from above the upper central incisor to the lowest part of the nasal septum; action: widens nasal aperture
Levator Labii Alaeque Nasi - the medial slip of this muscle enters the ala; action: the alar slip dilates the nostril
<
Diagram showing the muscles of the nose, adapted from a drawing by Hans
Arkeveld, Western Australia.
With all the current interest in plastic surgery of the nose and problems such as sleep apnoea, the anatomical arrangement of the nose is being re-examined, and some recent observations suggest that the standard accounts in anatomical textbooks require updating. If you are interested in these discussions, consult Daniel and Letourneau, (1988); Bruintjes et al (1996); Hoeyberghs et al (1996); and Oneal et al (1996).
References
Bruintjes, T.D., van Olphen, A.F., and Hillen, B. (1996) Review of the functional anatomy of the cartilages and muscles of the nose. Rhinology, 34(2), 66-74 (Jun).
Daniel, R.K., and Letourneau, A. (1988) Rhinoplasty: nasal anatomy. Annals of Plastic Surgery, 20(1), 5-13 (Jan).
Gray’s Anatomy (1989) 37th edition edited by P.L. Williams, R. Warwick, M. Dyson, and L.H. Bannister. Edinburgh: Churchill Livingstone (pp 570-573).
Hoeyberghs, J.L., Desta, K., and Matthews, R.N. (1996) The lost muscles of the nose. Aesthetic Plastic Surgery, 20(2), 165-169 (Mar-Apr).
Oneal, R.M., Beil, R.J. Jr, and Schlesinger, J. (1996) Surgical anatomy of the nose. Clin Plastic Surgery, 23(2), 195-222 (Apr).
If you exercise for 6 weeks doing weightlifting and your muscles get bigger why have they got bigger what causes the muscles to get bigger in size?
2nd September 2000
The muscles adapt to the extra work they are having to do by making more myofilaments inside each muscle fibre. Myofilaments are special thread-like proteins called actin and myosin that overlap each other and move in relation to each other to produce the muscle contraction. They use chemical energy to achieve the contraction and do work. Each muscle fibre, or muscle cell, has a cylindrical shape and as new myofilaments are created inside in response to the weight training, the diameter of each fibre increases. Since each muscle is made up of many, many muscle fibres in bundles alongside each other, the result is that the muscles increase in bulk as the training continues. When planning a weight training programme, it is important to include rest days to allow the muscles to synthesise new myofilaments and to repair any minor damage that is caused by the increasingly heavy loads they are experiencing.
What are the medical names for the muscles being worked when doing the following weight training exercises: bench press, incline bench press, squats, clean and jerk?
7th October 2000
Generally muscles work together in co-ordination to bring about work, balance, joint stability and posture. Weight training exercises and programmes have been developed to put particular muscles, or even localised parts of muscles, under controlled and progressive stress so that they will respond by growing in strength and bulk over time. Even so, it is worth remembering that exercising with heavy weights will put stress on many muscles throughout the body, not just the ones being targeted by the exercise. This is mentioned in case the following selections of muscle names give a false impression that they are the only ones being affected by the named exercise.
Bench Press
In this exercise, the person lies on their back on a low horizontal bench and raises and lowers a barbell with their arms. The main muscles being trained are the muscles of the front of the chest: pectoralis major and pectoralis minor (known to bodybuilders as the ‘pecs’), and the muscle called triceps at the back of each upper arm that has the action of extending (straightening) the the upper limb at the elbow. It may seem paradoxical that the same muscles are used in both phases of the exercise, lifting and lowering. As the bar is lowered towards the chest, the pectoral muscles and triceps are ‘paying out’ (lengthening) under control, and are still actively working against gravity and the weight. Subsidiary muscles that assist in the exercise are the anterior fibres of deltoid, the rotator cuff of muscles that stabilise the shoulder joint, the flexor muscles of the forearm that enable hands to grip the barbell, and the muscles involved in respiration. Remember, breathing while training is crucial, and must be co-ordinated with the exercise. Many other muscles will be playing a background role by stabilising the body’s position.
Incline Bench Press
The muscles involved are similar to those outlined for the bench press, with the main difference being that the incline bench press is designed to put more stress specifically on the upper fibres of pectoralis major muscle. Pectoralis major is a fan-shaped muscle that has an extensive medial attachment to the ribs, sternum, and clavicle and then narrows down to its attachment to the humerus. Thus, the upper fibres are passing laterally and slightly downwards, the middle fibres are passing laterally, and the lower fibres are passing laterally and upwards. By the use of incline, decline, and standard bench press exercises it is possible to target specific parts of pectoralis major.
Squats
In the front squat exercise, the barbell rests across the front of the chest and shoulders, the hands hold the bar slightly wider than shoulder-width, and the back is straight. The body is lowered into the squatting position and then the legs straighten vigorously to return the body to the upright starting position. This exercise particularly develops the quadriceps muscle (‘quads’) of the front of the thigh and the gluteal muscles (‘glutes’) of the buttock. Quadriceps, as the name suggests, is a four-part muscle: rectus femoris, vastus medialis, vastus intermedius, and vastus lateralis. The most powerful muscle of the gluteal group is gluteus maximus, while gluteus medius and gluteus minimus are smaller and placed more deeply. As mentioned for the other exercises, many other muscles will assist during this exercise, both by producing required movements and by stabilising joints and other structures that need to resist movement. Thus, many other muscles in the leg, thigh, and trunk will be active, as will muscles in the upper limbs as they support the barbell. If you palpate (feel) the hamstring muscles at the back of the thigh as the lifter carries out the squat exercise, you will begin to appreciate the complexity of muscle action. The line of action of the hamstrings is behind the hip joint and behind the knee, which would suggest that they produce extension of the hip and flexion of the knee. Although the activity of hip extensors is required during the squat, active flexion of the knee is not, so it is interesting to see (or feel) how these powerful muscles act during this heavily-loaded exercise. As noted for the other exercises, breathing must also be co-ordinated with the exercise.
Clean & Jerk
This is a complex exercise that will involve many if not most muscle groups. When good lifting technique is being used, the barbell will travel upwards from the floor along a vertical path, but to achieve this the lifter has to shift position in relation to the bar in order to maintain balance at all times. The muscles most active during the clean phase, during which the weights are lifted from the floor until the bar lies across the chest, are similar to those described for the squat exercise (above). Then the legs are straightened and the bar is lifted above the head until the elbows can be steadied in the straight-arm position.
The major upper body muscles that are working hard during this second phase of the exercise are the deltoid, upper fibres of pectoralis major, trapezius, serratus anterior, and triceps. We must also remember the role of the muscle groups of the back such as erector spinae as they stabilise the vertebral column during the lift.
I have a teacher who talks about one of the 'major muscles' being the psoas. While dissecting cadavers several years back, I was not impressed with the 'size' of the psoas. What do you think?
23rd November 2001
Psoas major is indeed a significant muscle - it attaches above to the lateral side of the lumbar vertebral column and below to the lesser trochanter of the femur. At the lower attachment it is joined by the iliacus muscle. The main action of the psoas is as a flexor of the thigh at the hip joint, assisted by iliacus. In about 60% of people there is a small muscle lying along the front of psoas major. It arises from the sides of vertebrae T12 and L1 and ends in a long tendon attached to the pecten pubis and iliac fascia. It is called psoas minor - I wonder if that is the muscle that you identified during dissection?
Recently I attempted a GCE O level paper of biology conducted by Cambridge University. There was a question: How are the muscles attached to the joints? I answered: ligaments, but people say the answer is tendons. If somebody wrote ligaments instead of tendons how many marks will you award him out of 5?
30th May 2004
Usually muscles that bring about movements at joints are attached to bones on each side of the joint, and not to the joints themselves. A skeletal muscle can attach to bones in several different ways. One way is to attach directly, a ‘fleshy’ attachment. Another way is by a tendon. This is a strong, fibrous strand that links a muscle belly to a bone. You can feel a strong tendon at the back of your heel – the Achilles tendon. A ligament extends directly from one bone to another and helps to strengthen the joint by stopping it from moving too far or becoming dislocated – a ligament is not linked with a muscle. However, the ligaments are made of the same material as the tendons – fibrous connective tissue. Tendons and ligaments are very strong. If they are damaged, they take a long time to heal because they do not have a rich blood supply.
You ask: If somebody wrote ligaments instead of tendons how many marks will you award him out of 5? I think some credit can be given because of the similar structure of tendons and ligaments – maybe 1 or 2 marks.
I have tried so hard to find the three types of muscle tissue found in the:
Stomach Wall
Uterus
Heart
Muscles attached to the joint
...I really couldn't find it anywhere.
9th December 2004
There are three histologically distinct types of muscle tissue in the body: smooth muscle, cardiac muscle, and skeletal muscle.
The wall of the stomach contains smooth muscle, which is composed of non-striated cells under involuntary control. In the part of the stomach referred to as the ‘body’, there are three layers of muscle, each with the muscle cells arranged in different orientations - the outer layer has longitudinally-arranged cells, the middle layer has circularly-arranged cells, and the inner layer has obliquely-arranged cells. Other parts of the stomach wall lack the inner oblique layer.
The muscular component of the uterus is also made of smooth muscle and is called the myometrium. The inner fibres of the myometrium are interwoven in various directions. These fibres contract, for example, during childbirth.
The heart is largely formed of specialised cardiac muscle cells. These striated, branching cells form an interconnecting network, again controlled involuntarily. The muscle layer is called the myocardium (myo- = muscle, -cardium = heart).
Smooth muscle cells and cardiac muscle cells each contain a single nucleus.
Muscles that produce movement at joints are made of skeletal muscle cells. These long, cylindrical cells are multi-nucleated and striated, and are under voluntary control.