Session 6 Bony Bits in Detail

Transcription

1 Session 6 Bony Bits in Detail Australian Institute of Fitness 1 / 38

2 SETTING THE SCENE Building on the knowledge gained in the previous session where we introduced the skeletal system, we now address the divisions of the skeleton and the key bony landmarks of the major bones of the body. We also examine the vertebral column in detail and finish with a practical workshop on posture. By the end of this session you will be able to identify and name the major bones of the body and their major bony landmarks. In addition, you will have knowledge of the natural curvatures of the spine (neutral spine) and what good posture is all about and how you teach it! Australian Institute of Fitness 2 / 38

3 DIVISIONS OF THE SKELETAL SYSTEM Let's start with the divisions of the skeletal system. The adult human skeleton consists of 206 bones of various sizes and shapes and is divided into two principle divisions: the axial skeleton and the appendicular skeleton. Australian Institute of Fitness 3 / 38

4 The Axial Skeleton The axial skeleton is so-called because it consists of the bones that lie around the longitudinal axis (vertical line) of the body. It is the skeleton s centre and consists of 80 bones and has the function of supporting the main axis of the body whilst protecting vital organs. Bones of the skull, spine and chest are included in the axial skeleton. The 80 bones of the axial skeleton include: Bones of your skull which include your jawbones (maxilla and mandible) = 22 Bones in your middle ear = 6 Bones in your vertebral column = 26 Sternum and 12 pairs of ribs in your thorax = 25 Hyoid bone in your neck which aids tongue movement and swallowing = 1 Australian Institute of Fitness 4 / 38

5 The Appendicular Skeleton The appendicular skeleton is so-called because it consists of the bones of the appendages, in other words, your arms and legs! There are 126 bones in the upper and lower limbs, and this includes those of the girdles that join the limbs to the axial skeleton (shoulder and pelvic girdles). Bones of the arms, legs, shoulder, pelvis, wrist, ankles, hands and feet are included in the appendicular skeleton. The 126 bones of the appendicular skeleton include: Your bones known as the clavicle (collarbone) and scapula (shoulder blade) in the shoulder girdle = 4 Bones in your fingers, hands and arms of the upper limb = 60 Your pelvis in the pelvic girdle = 2 Bones in your toes, feet and legs of the lower limb = 60 Australian Institute of Fitness 5 / 38

6 Bony Landmarks Have you noticed that bones have bumps, dips, pointy bits and that some even have sharp edges? These are known as bony landmarks and provide surface markings and structural features for specific functions. Most of these bony landmarks are not present from birth but develop in response to certain forces and are most prominent in the adult skeleton. In response to tension on a bone surface from tendons, ligaments and fascia, new bone is deposited, resulting in raised or roughened areas. Conversely, compression on a bone results in a depression. There are two major types of bony landmarks the dips and the bumps. The dips depressions and openings allow for the passage of soft tissue structures (such as blood vessels and nerves) or they form joints. The bumps processes are projections or outgrowths that either help form joints or serve as attachment points for connective tissue (such as ligaments and tendons). The Dips and Bumps Having an awareness of the dips and bumps terminology helps us understand the names of the bony landmarks. Dips: Foramen = opening through which blood vessels, nerves or ligaments pass such as the intervertebral foramen between the vertebra where the spinal nerves emerge from the spinal cord Fossa = shallow depression Sulcus = furrow along a bone surface that accommodates a blood vessel, nerve or tendon Bumps that form joints: Condyle = large, round protuberance at the end of a bone such as the condyles of the femur Facet = smooth flat articular surface such as the articular facets of the vertebrae Head = rounded articular projection supported on the neck of a bone such as the head of the humerus Bumps for attachment points: Crest = prominent ridge such as the iliac crest of ilium (pelvis) Epicondyle = projection above a condyle such as the epicondyles of the humerus Line (linea) = long narrow ridge or border, less prominent than a crest such as the linea aspera of the femur Spinous process = sharp slender projection such as the spinous process of the vertebrae Trochanter = very large projection such as the greater trochanter of the femur Tubercle = small rounded projection such as the greater tubercle of the humerus Tuberosity = large, rounded, usually roughened projection such as the ischial tuberosity of the ischium (pelvis) Some of these are 'need to know' such as the acromion process of the scapula but the majority are 'nice to know'. Australian Institute of Fitness 6 / 38

7 Coach Tip Australian Institute of Fitness 7 / 38

8 SKULL The bones of the skull are divided into three types according to their location: cranial bones, facial bones and ear bones. A need to know is the mastoid process a bump behind the ear which is a site of muscle attachment. Australian Institute of Fitness 8 / 38

9 VERTEBRAL COLUMN The vertebral column, also called the backbone, is the bony part of the spine and makes up about two-fifths of your total height. It functions as a strong, flexible rod with elements that can move forward, backward, sideways, and rotate. In addition to enclosing and protecting the spinal cord, it supports the head and serves as a point of attachment for ribs, pelvic girdle and muscles of the back and upper limbs. The adult vertebral column consists of 26 individual bones called vertebrae (vertebra is singular) which are stacked on top of each other much like a stack of building blocks. It is divided into five sections, each with its own natural curvature (concave or lordotic, and convex or kyphotic). Let s examine these now. 1. Cervical consists of 7 vertebrae and makes up the neck area (concave, lordotic) 2. Thoracic consists of 12 vertebrae and makes up the upper back area (convex, kyphotic) 3. Lumbar consists of 5 vertebrae and makes up the lower back area (concave, lordotic) 4. Sacrum consists of 5 fused sacral vertebrae. They begin fusing together between the ages of 16 and 18 years and complete their fusion by the mid-twenties (convex, kyphotic) 5. Coccyx consists of 4 fused coccygeal vertebrae and makes up the tail bone. Fusion generally occurs between the ages of 20 and 30 years Each vertebra is named according to its number in each section from superior to inferior, e.g., C1 is the first cervical vertebra at the base of the skull. Australian Institute of Fitness 9 / 38

10 Spinal Curvature As the images show in the previous section, the vertebral column is not completely straight but has a series of counterbalancing curves (kyphotic/lordotic) known as spinal curves. These spinal curves must be maintained during rest and activity. You may also hear these curves referred to as the natural curvature of the spine or the S shape of the spine and in exercise, we use the term neutral spine to describe this curvature. The curves are important for both movement and to dissipate forces. If there were no curves, the downward compression forces would be greater and this would accelerate wear and tear. We will discuss spinal alignment in more detail during the posture section later in the session. Some facts: The spinal curves only begin to appear in the infant when they begin to bear weight. The functions of the curves include support, strength and balance. There is minimal movement between each intervertebral joint, but as a whole unit the spine can move through a large range of movement. Low back pain involves a dull or continuous pain in the lumbar region, and is the most common cause of disability and time lost from work for people years of age; this affects 80% of the population at some stage in their life. Australian Institute of Fitness 10 / 38

11 Vertebrae There are distinct differences between each of the vertebrae. The most obvious is size. The lumbar region, being a weight bearing area, has larger vertebrae so as to withstand large compressive forces. The cervical region on the other hand is designed for mobility therefore the vertebrae are smaller. Remember, more mobility equals less stability! There are also differences in the bony structures around the vertebrae. The lumbar spine has a larger supporting joint structure that limits its range of movement, therefore increasing its stability, whereas the cervical vertebrae has less bony surfaces around it so as to enhance its mobility, at a cost to stability. The thoracic vertebrae can also be identified by their size and surrounding bony structures. Since the ribs connect to the thoracic vertebrae the ribs can also be used to identify them. Interestingly enough, there are 12 thoracic vertebrae and 12 pairs of ribs! Australian Institute of Fitness 11 / 38

12 Vertebral Bony Landmarks While there are differences between the vertebrae, they do have similar bony landmarks which are important attachment points. Here are the need to know bony bits: Body of vertebra the actual building blocks of the vertebral column Spinous process the bumps we feel when we run our fingers down the spine Intervertebral disc the cushions in between the moveable vertebrae of the spine Nice to Know Vertebral foramen the opening in all vertebrae through which the spinal cord passes Intervertebral foramen the opening in between the vertebrae through which the spinal nerves emerge from the spinal cord Australian Institute of Fitness 12 / 38

13 Intervertebral Discs The intervertebral discs are found between the moveable vertebrae of the spine. They allow movement at each intervertebral joint, prevent degeneration of the articulating vertebrae and absorb compression forces through the spine. The discs consist of a fibrous outer rim known as the annulus fibrosus and a centre known as the nucleus pulposus. Regardless of popular thought, the discs cannot slip out; they are firmly attached to the vertebrae. But if the discs experience repetitive forces in an unbalanced way, which could happen with repetitive movement or as a result of poor posture, it may lead to greater wear and tear of the disc. If a disc becomes damaged and inflamed, it can compromise the surrounding structures and may require medical attention. The diagram below shows a herniated disc notice how the spinal cord and nerve are compromised. Australian Institute of Fitness 13 / 38

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15 Disc Pressure and Forward Flexion Disc pressure is least when lying supine. It increases as we stand, and increases more as we sit, especially if we slouch and the lumbar curve decreases. A chair that has a lumbar support to maintain the lumbar lordosis will place the least amount of pressure on the discs. Good postural alignment while sitting at rest and during exercise is important, as this position can place a great deal of pressure on the intervertebral discs. Be aware of too much forward flexion Leaning forward (forward flexion) in any position increases the disc pressure, and leaning forward with a weight in our hand obviously increases it more! Hence, we need to avoid slouching and for any exercises done in a bent-over position or that require us to lean forward, they should be performed with the best neutral spine possible. Australian Institute of Fitness 15 / 38

16 Coach Tip Australian Institute of Fitness 16 / 38

17 THORAX The thorax is formed through the articulation (or joining) of the thoracic vertebrae, ribs and sternum. Together these structures make up the thoracic cage (often referred to as the thorax or chest). The component parts of the thorax are as follows: Bone Sternum Ribs Description The flat bone commonly referred to as the breastbone; bony landmarks include the manubrium superiorly and the xiphoid process (cartilaginous) inferiorly Twelve pairs of ribs arranged into true and false ribs True ribs are the superior seven pairs that articulate with the sternum at costal cartilages False ribs are the inferior five pairs (upper three pairs articulate with costal cartilage of the seventh pair of true ribs, and the lower two pairs do not have an anterior articulation, thus are referred to as 'floating' ribs) Australian Institute of Fitness 17 / 38

18 SHOULDER GIRDLE The body has two shoulder girdles that attach the bones of the upper limb to the axial skeleton. Each of the shoulder girdles consists of a clavicle and a scapula. The clavicle articulates medially with the sternum to form the sternoclavicular joint. Each scapula or shoulder bone works with the clavicle to form the shoulder girdle. Here are the need to know bony bits of the scapula which are labelled on the images below. After viewing the video, try to palpate these on the scapula of a friend or family member you can find some of these on yourself as well. Glenoid cavity (the socket) Acromion process Coracoid process Spine of scapula Medial border Inferior angle Australian Institute of Fitness 18 / 38

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20 UPPER LIMB Each upper limb has 30 bones in three locations: Humerus in the upper arm = 1 The ulna and radius in the forearm = 2 The 8 carpals in the wrist, the 5 metacarpals in the palm and the 14 phalanges making up the digits of the hand = 27 Here are the need to know bony bits which are labelled on the images below. After viewing the video, locate these on yourself (head and neck of humerus are deep but you should be able to palpate the others). Head of the humerus Greater tubercle of the humerus Neck of the humerus Medial and lateral epicondyles on the bottom of the humerus Olecranon of the ulna (funny bone) Australian Institute of Fitness 20 / 38

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22 Snapshot - Shoulder Girdle and Upper Extremities Bone Clavicle Scapula Humerus Radius Ulna Carpals Metacarpals Phalanges Description Two bones referred to as collar bones; they form the sternoclavicular joint where it articulates with the sternum Two bones referred to as shoulder blades; they work with clavicles to form shoulder girdle; bony landmarks include the acromion process, coracoid process, spine of scapula, glenoid cavity and inferior angle Two bones that are the upper arm bones; bony landmarks include the head of humerus, medial and lateral epicondyles, greater tubercle, surgical neck and trochlea Two bones that are the lateral forearm bones; bony landmarks include the styloid process and radial tuberosity Two bones that are the medial forearm bones; bony landmark is the olecranon process ('funny bone') The short bones located at the wrist (eight on each limb) The long bones of the palm (five on each hand) The long bones of the digits (three in each finger, two in each thumb) Australian Institute of Fitness 22 / 38

23 PELVIC GIRDLE The hip or pelvic girdle consists of two hip bones, also called pelvic bones. Each pelvic bone is comprised of three fused bones in the adult: Ilium Ischium Pubis The pelvic bones unite anteriorly at a joint called the pubic symphysis. They unite posteriorly with the sacrum at the sacroiliac joints. The complete ring composed of the hip bones, pubic symphysis and sacrum forms a deep, basin-like structure called the bony pelvis. Functionally, the bony pelvis provides a strong and stable support for the vertebral column and pelvic and lower abdominal organs. The pelvic girdle of the bony pelvis also connects the bones of the lower limbs to the axial skeleton. Australian Institute of Fitness 23 / 38

24 Here are the need to know bony bits. Find them on the above images. You can feel three of the four landmarks on yourself. Which ones are they and where are they? Acetabulum Symphysis pubis Iliac crest Anterior superior iliac spine (ASIS) Australian Institute of Fitness 24 / 38

25 "Nice to Know" - Shoulder and Pelvic Girdles There are some significant differences between the shoulder and pelvic girdles. The shoulder girdle does not directly articulate with the vertebral column, but the pelvic girdle does via the sacroiliac joint. The joint sockets (glenoid fossae) for the upper limbs in the shoulder girdle are shallow to maximize movement; in contrast the sockets (acetabula) for the lower limbs in the pelvic girdle are deep and allow less movement. Overall the structure of the shoulder girdle offers more mobility than strength, and that of the pelvic girdle offers more strength than mobility. Australian Institute of Fitness 25 / 38

26 LOWER LIMB Each lower limb has 30 bones (just like the upper limb) but in four locations: The femur in the thigh = 1 The patella in the knee = 1 The tibia and fibula in the leg = 2 The 7 tarsals in the ankle, the 5 metatarsals in the midfoot and the 14 phalanges making up the digits of the foot = 26 Here are the need to know bony bits which are labelled on the images below. Try to locate the position of these landmarks on yourself. Head of femur Neck of femur Greater trochanter Lateral and medial epicondyles on the bottom of the femur Australian Institute of Fitness 26 / 38

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28 What About the Lower Leg? The fibula is the lateral leg bone and has the need to know bony landmarks of: Head of fibula Lateral malleolus (ankle bone) The tibia is the shinbone and has the need to know bony landmarks of: Lateral and medial condyles (top of tibia) Tibial tuberosity (bump just under the patella) Medial malleolus (ankle bone) The other really important bone to know is your heel bone. It is one of the tarsal bones and is named 'calcaneus'. It is important because it is the attachment site for your calf muscles via the Achilles tendon. Australian Institute of Fitness 28 / 38

29 Snapshot - Pelvic Girdle and Lower Extremities Bone Pelvis Femur Patella Tibia Fibula Tarsals Metatarsals Phalanges Description Two pelvic bones, each composed of three fused bones (ilium, ischium and pubis); bony landmarks include the acetabulum, symphysis pubis, iliac crest, anterior superior iliac spine (ASIS) and pelvic inlet Two bones that are the thigh bones; bony landmarks include the head of femur, neck of femur, lateral and medial epicondyles, greater and lesser trochanters and lateral and medial condyles Two bones that are the kneecaps, referred to as sesamoid bones (bone encased in tendon); bony landmark superior border of the patella Two bones that are the shin bones; bony landmarks include the lateral and medial condyles, tibial tuberosity and medial malleolus Two bones that are the lateral lower leg; bony landmarks include the head of fibula and lateral malleolus Bones that form the heel and hind foot (seven on each foot); the tarsal bone referred to as the calcaneus forms the heel The long bones of the foot, superior to arches of foot: longitudinal and transverse arches (five in each foot) The long bones of the digits (three in each toe, two in the big toe) Australian Institute of Fitness 29 / 38

30 GOOD POSTURE In general, posture is the position of your body parts in relation to each other at any given time. Posture can be static, as in a stationary position such as standing, or dynamic as the body moves from one position to another. Posture deals with alignment of the various body segments your head, spine, arms and legs, and even your feet. Good posture can be defined as the ideal position or alignment of the body which minimises stress, is most energy efficient and allows for sound body mechanics. Good posture is important because it decreases the amount of stress placed on bones, ligaments, muscles and tendons. Good alignment also improves function and decreases the amount of muscle energy needed to keep the body upright. For example, if the knee is in full extension, little muscle contraction is needed to keep the knee from buckling. However, when the knee is partially flexed, the quadriceps must contract to keep the knee from collapsing. This requires more muscle energy. If the body segments are in the correct alignment, the body would remain relatively stable. But if you stack them slightly off centre from each other, the body will only remain upright if the segments above counter those below. This, in essence, is what the spinal curves achieve. In the human body, each joint involved in weight bearing is associated with posture. Australian Institute of Fitness 30 / 38

31 Neutral Spinal Alignment As we have just learnt, the vertebral column consists of 26 individual bones stacked on top of each other. It is not completely straight; each region of the vertebral column has its own natural curve. We have previously mentioned that these curves are referred to as the natural curvature of the spine or the S shape of the spine and in exercise, we use the term neutral spine. It is important to adopt and maintain a neutral spine during all training in all exercises the back should be still and stable. A neutral spine is thought to: Ensure a higher tolerance of the joints to withstand compression forces Reduce risk to ligaments of the spine Reduce risk of disc herniation In other words, a neutral spine is the strongest position it is no coincidence that Olympic weightlifters adopt a neutral spine. The thoracic and sacral curves are kyphotic curves and the lumbar and cervical curves are lordotic curves. When one or more of these vertebral curves either increases or decreases significantly from what is considered good posture, poor posture results. For example, excessive lordosis is an increased lumbar curve, whereas excessive kyphosis is an increased thoracic curve. Australian Institute of Fitness 31 / 38

32 Sitting Posture As already mentioned, intervertebral disc pressure is greatest in a seated position hence when exercising in this position, particularly with load, care must be taken to ensure the best posture possible. Let s use the example of a seated cable row. If neutral spine is not maintained and the person slouches, the pressure on the intervertebral discs and posterior structures increases. In the case of a supported seated row, adding the back rest or chest pad reduces pressure. The elements of good seated posture are: Trunk upright and neutral spine maintained Keep neck in line with spine Shoulders down in a normal position Where possible, support the lower back or a front support Keep feet flat on the floor Position seat so that hips are slightly higher than knees In addition, never pick up or put down your weights while seated as it is very stressful for your back. Instead, use your legs (not your back) by standing, then using a deadlift action to lower/collect equipment. Australian Institute of Fitness 32 / 38

33 Standing Posture - Plumb Line Posture is easier to describe in a static standing position because, except for a slight amount of sway when standing, the body is not moving. However, many of the guidelines for static posture can be applied to dynamic posture. Assessing a person s posture can be done with the use of a plumb line suspended from the ceiling or a posture grid behind the person as a point of reference. A plumb line is a string or cord with a weight attached to the lower end. Because the string is weighted, it makes a perfectly straight vertical line of gravity. Did you know that you can make a simple plumb line by using brickies string and a plumb or fishing line sinker? Australian Institute of Fitness 33 / 38

34 How to Use the Plumb Line In the standing position and viewed from the lateral position (side on), a straight vertical line should pass through the earlobe and slightly in front of the lateral malleolus. For ideal posture the body segments should be aligned so that the straight vertical line passes through the landmarks as follows: Head through the earlobe Shoulder through the tip of the acromion process Thoracic spine anterior to the vertebral bodies Lumbar spine through the vertebral bodies Pelvis level Hip through the greater trochanter (slightly posterior to the hip joint axis) Knee slightly posterior to the patella (slightly anterior to the knee joint axis) with the knees in extension Ankle slightly anterior to the lateral malleolus with the ankle joint in a neutral position (feet flat on the floor) Everyone s posture will be slightly different. Start developing the skill of assessing posture to improve your awareness of postural non-alignments. Keep in mind that they could be structural (very hard to change) or functional, resulting from lifestyle habits such as slouching, footwear, seating or carrying. These of course can be addressed and posture can be improved thus helping your clients to look and feel better! To improve posture stretch what s tight and strengthen what s weak. Australian Institute of Fitness 34 / 38

35 Maintaining Great Posture When actively moving about and changing positions, whether dodging a ball, picking up a weight plate from the floor or running on a treadmill, keeping the body especially the trunk in good postural alignment is important. Most principles of good body mechanics involve avoiding stress to the trunk and maintaining the spinal curves, which involve maintaining good posture! Here are five key areas of posture that you should be aware of: Area Head and neck Shoulders/scapula Neutral spine/pelvis Knees Feet Posture tip Ear over shoulder, slight chin tuck, eyes on horizon Shoulders down and neutral, elbows straight, palms by thighs Natural curvature, gentle abdominal brace, pelvis level Soft, patella in line with second toe Even weight distribution Australian Institute of Fitness 35 / 38

36 Your Turn Posture Check Visit your Your Turn Diary and complete some activities to cement your understanding of good posture. You will need a friend or familty member to practice on. Australian Institute of Fitness 36 / 38

37 ROUND UP By now, you should have a good appreciation of the skeletal system and getting to know your bony bits! Have a look at what we ve achieved these are the key areas of learning. The axial skeleton The appendicular skeleton Bony landmarks Vertebral column Spinal curvature Vertebrae Intervertebral discs Thorax Shoulder girdle Upper limb Pelvic girdle Lower limb Good posture Neutral spinal alignment Sitting posture Standing posture plumb line Maintaining great posture As a fitness professional, we need to walk our talk and practise what we preach so if you have any bad postural habits, see if you can improve your posture first! Practice makes perfect! During your own personal workouts, remind yourself of the perfect postures from an earlier session and now that you know more about posture, fine-tune the starting positions of all the exercises you perform. Later in our course, we will go into posture in more detail starting with some common postural abnormalities and how to improve posture. Australian Institute of Fitness 37 / 38

38 REFERENCES The following resources were used in the compilation of this session: Tortora, G.J. and Derrickson, B. (2009). Principles of Anatomy and Physiology, 12th edition. John Wiley & Sons: NJ Thibodeau, G.A. and Patton, K.T. (2004). Structure and Function of the Body. Mosby: St Louis Australian Institute of Fitness 38 / 38