Cartilaginous constraints

Cartilage has the consistency of rubber or soil plastic. It gives shape to the nose and external ears, and it forms a cushioning layer at the ends of long bones. Our main concern in this discussion, however, is not with these examples but with the joints called symphyses—the intervertebral disks between adjacent vertebral bodies (figs. 1.11,4.10b. 4.11, and 4.13b), as well 38 the pubic symphysis between the two pubic bones (figs. 1.12 and 3.2). At of these sites symphyses restrict movement, something like soft but thick rubber gaskets glued between blocks of wood that allow a little move-Went but no slippage. To that end the pubic symphysis is secure enough to bind the two halves of the pelvic bowl together in front and yet permit Postural shifts and deviations; intervertebral disks bind adjacent vertebrae together tightly and yet permit the vertebral column as a whole to bend an<J twist.

54 AMTHM) OF HAI HA YOGA

ulna medial view of right elbow joint radius

Right Elbow Joint Medial View Bones

olecranon process humerus ulnar collateral ligament, two bands olecranon process medial view of right elbow joint radius

humerus ulnar collateral ligament, two bands

Coronoid And Radial Fossa

coronoid fossae ulnar collateral ligaments-

olecranon processes coronoid processes radial fossa radial collateral ligament right radius radial collateral ^ligament left radius radial fossa right humerus disarticulated elbow joints, front views left humerus coronoid fossa coronoid process

Olecranon Fossa

humerus olecranon fossa olecranon process ulna coronoid fossa coronoid process

Figure 1.10. Bony stops for elbow flexion and extension, with the joint capsule pictured above, front views of the disarticulated right and left elbow joints shown in the middle, and a longitudinal cut through the joint and two of its three bones shown below. Extension is stopped where the olecranon process butts up against its fossa, and flexion is stopped where the head of the radius and coronoid process butt up against the radial and coronoid fossae (Sappey).

i MovFMf.vrAixn POSTVRE 55

tendons and ligaments

By definition, tendons connect muscles to bones, and ligaments connect bone to bone. They are both made up of tough, ropy, densely packed, inelastic connective tissue fibers, with only a few cells interspersed between large packets of fibers. Microscopically, tendons and ligaments are nearly identical, although the fibers are not packed as regularly in ligaments as in tendons. In a tendon the fibers extend from the belly of a muscle into the substance of a bone, lending continuity and strength to the whole complex. Ligaments hold adjoining bones together in joints throughout the body, often permitting small gliding motions, and usually becoming taut at the end of a joint's range of motion.

Ligaments and tendons can accommodate no more than about a 49e increase in length during stretching, after which tearing begins. This can be a serious problem. Because the extracellular connective tissue fibers in tendons and ligaments depend only on a few scattered living cells for repair and replacement, and because the tissue is so poorly supplied with blood vessels, injuries are slow to heal. The most common of these is tendinitis, which is caused by tears in the fibers at the interface between tendon and

inferior articulating process of L5

spatial orientation of articulating processes prevents lumbar twisting of L1 inferior articulating process of LI (right side)

superior articulating process of L2 (right side)

rear view of right transverse process of rear view of spinous process of L4

superior articulating process of L1

Ul LI

spinous

"gure 1.11. Lumbar vertehrae from the front, side, and hehind. The vertical, font-(o-back orientation of the articulating processes and their joint surfaces Provides a bony strip that prevents lumbar twisting. Spaces that represent the at ion for the intervertebral disk between L2 and L3 are indicated by arrows (Sappey.)

56 ASATOMY OF HATHA XX,A

bone. If someone keeps abusing this interface with repetitive stress, whether typing at a computer keyboard, swinging a tennis racket, or trying compulsively to do a stressful hatha yoga posture, the injury can take a year to heal, or even longer.

The main purpose of ligaments is to restrain movable joints, and this becomes a major concern in hatha yoga when we want to stretch to our maximum. We might at first think of loosening them up and stretching them out so they do not place so many restraints on hatha postures. But ligaments don't spring back when stretched and lengthened (at least not beyond their 4% maximum), and if we persist in trying to stretch them beyond their limits we often do more harm than good. Once lengthened they become slack, and the joints they protect are prone to dislocation and injury. Ligaments have their purpose; let them be. To improve ranges of motion and flexibility, it is better to concentrate on lengthening muscles.

joint capsules

Joint capsules are connective tissue encasements that surround the working surfaces of the class of joints known as synovial joints, including hinge joints, pivot joints, and ball-and-socket joints. Joint capsules for synovial right left pubic pubic bone bone right left pubic pubic bone bone

Cartilaginous Animal Joints Photo Pelvis
ischial tuberosities (sitting bones)

figure 1.12. Pubic symphysis shown where it joins the two sides of the pelvis. This enlargement of the two pubic bones and ischia (front view) is taken from %. 3.2, which shows the entire pelvis in perspective (Sappey).

joints have several roles: they provide a container for the slippery synovial fluid that lubricates the mating surfaces of the opposing bones; they house the synovial membrane that secretes the synovial fluid; they provide a tough covering of tissue into which ligaments and tendons can insert; and of special interest to us here, they and their associated ligaments provide about half the total resistance to movement.

The shoulder joint reveals an excellent example of a joint capsule. Like the hip joint, the shoulder joint is a ball and socket—the ball being the head of the humerus and the socket being the glenoid cavity of the scapula (fig. i.H). The joint capsule surrounds the entire complex and accommodates tendons that pass through or blend into the joint capsule, as well as ligaments that reinforce it on the outside. To feel how it restricts movement, raise your arm overhead and pull it to the rear as far as possible: within the shoulder you can feel the joint capsule and its ligaments tightening up.

EXTENSILE ligaments

Extensile ligaments are not really ligaments; they are skeletal muscles held at relatively static lengths by motor neurons firing a continuous train of nerve impulses. They have greater elasticity than connective tissue ligaments because of their muscular nature, but other than that they function to maintain our posture like ordinary ligaments. What they don't do, by definition, is move joints through their full range of motion, which is what we usually expect from skeletal muscles. According to the conventional definition, extensile ligaments are mostly postural muscles in the torso, but it is arguable that for maintaining a stable meditation posture, every muscle in the body (excepting the muscles of respiration) becomes an extensile ligament.

Unlike connective tissue ligaments, the length of extensile ligaments can be adjusted according to the number of nerve impulses impinging on the muscle. And since every muscle associated with the torso and vertebral column is represented on both sides of the body, the matching muscles in each pair should receive the same number of nerve impulses per second on each side, at least in any static, bilaterally symmetrical posture. Tf that number is unequal, the paired muscles will develop chronically unequal lengths that result in repercussions throughout the central axis of the body. In hatha yoga, this condition is especially noticeable because it is the primary source of right-left musculoskeletal imbalances.

Axial imbalances can be spotted throughout the torso and vertebial column, but they arc especially noticeable in the neck, where the tiny suboccipital Muscles function as extensile ligaments to maintain head position (fig. &20>. If your head is chronically twisted or tipped slightly to one side, it rna.V mean that you have held the matching muscles on the two sides at unequal lengths over a long period of time. Motor neurons have become

acromion ot scapula glenoid articular head of " humerus

Origin Triceps Brachii

medial border ot scapula tendon of ongin, long head of triceps brachii capsule of shoulder joint tendon of origin, long head of the biceps brachii

Biceps Brachii

tendon of origin, long head of triceps brachii tendons of insertion of 3 rotator cuff muscles capsule of shoulder joint tendon of origin, long head of triceps brachii

Long Head Triceps Brachii

neck of humerus

Figure 1.13. Disarticulated right shoulder joint as viewed from the front (top image); right shoulder joint with its capsule, also from the front (middle image); and right shoulder joint with its capsule as viewed from behind (bottom image). Envision the chest as being located in front of the scapula and to the observer's right in the top two images (the surface of the scapula shown here faces the back of the chest). In the bottom image, envision the back of the scapula as being located to the observer's left; except for being a much deeper and more confined dissection, this view is similar to the one shown in figure 1.1. Asterisks indicate stabilizing ligaments, and arrows indicate rotator cuff lendons (Sappey).

articular head of " humerus medial border ot scapula acromion ot scapula glenoid clavicle corocoid process of scapula tendon of ongin, long head of triceps brachii surface of scapula (faces back side of chest)

site of attachment of fibrous capsule of the shoulder joint to the rear border of the glenoid cavity capsule of shoulder joint tendon of origin, long head of triceps brachii tendon of origin, long head of triceps brachii subscapulars muscle takes origin from the front surface of the scapula (behind the chest) and helps hold the head of the humerus against the glenoid cavity tendon of insertion of the muscle, one of the rotator cuff muscles tendons of insertion of 3 rotator cuff muscles and teres minor; these muscles stabilize the shoulder joint and keep it from being dislocated neck of humerus capsule of shoulder joint tendon of origin, long head of the biceps brachii

Figure 1.13. Disarticulated right shoulder joint as viewed from the front (top image); right shoulder joint with its capsule, also from the front (middle image); and right shoulder joint with its capsule as viewed from behind (bottom image). Envision the chest as being located in front of the scapula and to the observer's right in the top two images (the surface of the scapula shown here faces the back of the chest). In the bottom image, envision the back of the scapula as being located to the observer's left; except for being a much deeper and more confined dissection, this view is similar to the one shown in figure 1.1. Asterisks indicate stabilizing ligaments, and arrows indicate rotator cuff lendons (Sappey).

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Responses

  • veera j
    What is coronoid fossa?
    6 years ago
  • Kibra
    How to tell a disarticulated right humerus from the left?
    6 years ago
  • sointu
    Where is the coronoid fossa located?
    6 years ago
  • alesha smith
    What are extensile ligaments?
    6 years ago

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