Cervical spinal nerve 8
The cervical spinal nerve 8 is a spinal nerve of the cervical segment. It originates from the spinal column from below the cervical vertebra 7; the C8 nerve forms part of the radial and ulnar nerves via the brachial plexus, therefore has motor and sensory function in the upper limb. The C8 nerve receives sensory afferents from the C8 dermatome; this consists of all the skin on the little finger, continuing up past the wrist on the palmar and dorsal aspects of the hand and forearm. Clinically a test of the pad of the little finger is used to assess C8 integrity; the C8 nerve contributes to the motor innervation of many of the muscles in the trunk and upper limb. Its primary function is the flexion of the fingers, this is used as the clinical test for C8 integrity, in conjunction with the finger jerk reflex; the particular muscles receive innervation from C8: Pectoralis major - Medial and lateral pectoral nerves Pectoralis minor - Medial pectoral nerve Latissimus dorsi - Thoracodorsal nerve Triceps brachii - Radial nerve Flexor carpi ulnaris - Ulnar nerve Palmaris longus - Median nerve Flexor digitorum superficialis - Median nerve Flexor digitorum profundus - Median and Ulnar nerves Flexor pollicis longus - Median nerve Pronator quadratus - Median nerve Extensor carpi radialis brevis - Deep branch of the radial nerve Extensor digitorum - Posterior interosseous nerve Extensor digiti minimi - Posterior interosseous nerve Extensor carpi ulnaris - Posterior interosseous nerve Anconeus - Radial nerve Abductor pollicis longus - Posterior interosseous nerve Extensor pollicis brevis - Posterior interosseous nerve Extensor pollicis longus - Posterior interosseous nerve Extensor indicis - Posterior interosseous nerve Palmaris brevis - Superficial branch of ulnar nerve Dorsal interossei - Deep branch of ulnar nerve Palmar interossei - Deep branch of ulnar nerve Adductor pollicis - Deep branch of ulnar nerve Lumbricals - Deep branch of ulnar nerve, Digital branches of median nerve Opponens pollicis - Recurrent branch of median nerve Abductor pollicis brevis - Recurrent branch of median nerve Flexor pollicis brevis - Recurrent branch of median nerve Opponens digiti minimi - Deep branch of ulnar nerve Abductor digiti minimi - Deep branch of ulnar nerve Flexor digiti minimi brevis - Deep branch of ulnar nerve
Scalene tubercle
The scalene tubercle is a small projection that runs along the medial border of the first rib between two grooves, which travel anteriorly for the subclavian vein and posteriorly for the subclavian artery. It is the site of insertion for scalenus anterior. Scalene muscle first rib
Platysma muscle
The platysma is a superficial muscle that overlaps the sternocleidomastoid. It is a broad sheet arising from the fascia covering the upper parts of the pectoralis major and deltoid. Fibres at the front of the muscle from the left and right sides intermingle together below and behind the symphysis menti, it is not a true symphysis. Fibres at the back of the muscle cross the mandible, some being inserted into the bone below the oblique line, others into the skin and subcutaneous tissue of the lower part of the face. Many of these fibers blend with lower part of the mouth. Sometimes fibers can be traced to the margin of the orbicularis oris. Beneath the platysma, the external jugular vein descends from the angle of the mandible to the clavicle. Variations occur over the clavicle and shoulder. A more or less independent fasciculus, the occipitalis minor, may extend from the fascia over the trapezius to fascia over the insertion of the sternocleidomastoideus; the platysma is supplied by cervical branch of the facial nerve.
When the entire platysma is in action it produces a slight wrinkling of the surface of the skin of the neck in an oblique direction. Its anterior portion, the thickest part of the muscle, depresses the lower jaw. However, the platysma plays only a minor role in depressing the lip, performed by the depressor anguli oris and the depressor labii inferioris. In a similar fashion to other muscles, the platysma is vulnerable to tears and muscle atrophy among many other possible conditions; the platysma is vulnerable to neck injuries. A type of medical imagining called CTA, used to visualise arterial and venous vessels, is useful to minimise the number of neck explorations, thus improving the handling of the condition. Another area of importance of the platysma lies in plastic surgery. Neck bands in the area become most noticeable with age, aggravated by facelift. If it doesn't heal with time, there are many options to correct this: Botox/Dysport/Xeomin and platysmaplasty. Platysmaplasty is a surgery in this area, that can be open or closed, in the latter a specialised instrument called plastymotome that allow the surgery to be done without incisions.
It takes 2 weeks for the symptoms to be reduced. This article incorporates text in the public domain from page 387 of the 20th edition of Gray's Anatomy BooksSusan Standring. Gray's anatomy: the anatomical basis of clinical practice. London: Churchill Livingstone. ISBN 978-0-8089-2371-8
Rib cage
The rib cage is the arrangement of ribs attached to the vertebral column and sternum in the thorax of most vertebrates, that encloses and protects the heart and lungs. In humans, the rib cage known as the thoracic cage, is a bony and cartilaginous structure which surrounds the thoracic cavity and supports the shoulder girdle to form the core part of the human skeleton. A typical human rib cage consists of 24 ribs in 12 pairs, the sternum and xiphoid process, the costal cartilages, the 12 thoracic vertebrae. Together with the skin and associated fascia and muscles, the rib cage makes up the thoracic wall and provides attachments for the muscles of the neck, upper abdomen, back; the rib cage has a major function in the respiratory system. Ribs are described based on their connection with the sternum. All ribs are numbered accordingly one to twelve. Ribs that articulate directly with the sternum are called true ribs, whereas those that connect indirectly via cartilage are termed false ribs. Floating ribs are not attached to the sternum at all.
The terms true ribs and false ribs describe rib pairs that are directly or indirectly attached to the sternum. The first seven rib pairs known as the fixed or vertebrosternal ribs are the true ribs as they connect directly to the sternum, their elasticity allows rib cage movement for respiratory activity. The phrase floating rib refers to the eleventh and twelfth rib pairs; these ribs are small and delicate, include a cartilaginous tip. The spaces between the ribs are known as intercostal spaces; each rib consists of a head, a shaft. All ribs are attached posteriorly to the thoracic vertebrae, they are numbered to match the vertebra -- one to twelve, from top to bottom. The head of the rib is the end part closest to the vertebrae, it is marked by a kidney-shaped articular surface, divided by a horizontal crest into two articulating regions. The upper region articulates with the inferior costal facet on the vertebra above, the larger region articulates with the superior costal facet on the vertebra with the same number.
The transverse process of a thoracic vertebra articulates at the transverse costal facet with the tubercle of the rib of the same number. The crest gives attachment to the intra-articular ligament; the neck of the rib is the flattened part. The neck is about 3 cm long, its anterior surface is flat and smooth, whilst its posterior is perforated by numerous foramina and its surface rough, to give attachment to the ligament of the neck. Its upper border presents a rough crest for the attachment of the anterior costotransverse ligament. On the posterior surface at the neck, is an eminence—the tubercle that consists of an articular and a non-articular portion; the articular portion is the lower and more medial of the two and presents a small, oval surface for articulation with the transverse costal facet on the end of the transverse process of the lower of the two vertebrae to which the head is connected. The non-articular portion is a rough elevation and affords attachment to the ligament of the tubercle.
The tubercle is much more prominent in the upper ribs than in the lower ribs. The angle of a rib may both refer to the bending part of it, a prominent line in this area, a little in front of the tubercle; this line is directed laterally. At this point, the rib is bent in two directions, at the same time twisted on its long axis; the distance between the angle and the tubercle is progressively greater from the second to the tenth ribs. The area between the angle and the tubercle is rounded and irregular, serves for the attachment of the longissimus dorsi muscle; the first rib is the most curved and the shortest of all the ribs. The head is small and rounded, possesses only a single articular facet, for articulation with the body of the first thoracic vertebra; the neck is rounded. The tubercle and prominent, is placed on the outer border, it bears a small facet for articulation with the transverse costal facet on the transverse process of T1. There is no angle, but at the tubercle, the rib is bent, with the convexity upward, so that the head of the bone is directed downward.
The upper surface of the body is marked by two shallow grooves, separated from each other by a slight ridge prolonged internally into a tubercle, the scalene tubercle, for the attachment of the anterior scalene. Behind the posterior groove is a rough area for the attachment of the medial scalene; the under surface is smooth and without a costal groove. The outer border is convex and rounded, at its posterior part gives attachment to the first digitation of the serratus anterior; the inner border is concave and sharp, marked about its center by the scalene tubercle. The anterior extremity is larger and
Trapezius
The trapezius is a large paired surface muscle that extends longitudinally from the occipital bone to the lower thoracic vertebrae of the spine and laterally to the spine of the scapula. It supports the arm; the trapezius has three functional parts: an upper part. The trapezius is used to nod your head, it is used to hold up your head. The trapezius muscle resembles a trapezium, or diamond-shaped quadrilateral; the word "spinotrapezius" refers to the human trapezius, although it is not used in modern texts. In other mammals, it refers to a portion of the analogous muscle; the term "tri-axle back plate" was used to describe the trapezius muscle. The superior or upper fibers of the trapezius originate from the spinous process of C7, the external occipital protuberance, the medial third of the superior nuchal line of the occipital bone, the ligamentum nuchae. From this origin they proceed downward and laterally to be inserted into the posterior border of the lateral third of the clavicle; the middle fibers, or transverse of the trapezius arise from the spinous process of the seventh cervical, the spinous processes of the first and third thoracic vertebrae.
They are inserted into the medial margin of the acromion, into the superior lip of the posterior border of the spine of the scapula. The inferior or lower fibers of the trapezius arise from the spinous processes of the remaining thoracic vertebrae. From this origin they proceed upward and laterally to converge near the scapula and end in an aponeurosis, which glides over the smooth triangular surface on the medial end of the spine, to be inserted into a tubercle at the apex of this smooth triangular surface. At its occipital origin, the trapezius is connected to the bone by a thin fibrous lamina adherent to the skin; the superficial and deep epimysia are continuous with an investing deep fascia that encircles the neck and contains both sternocleidomastoid muscles. At the middle, the muscle is connected to the spinous processes by a broad semi-elliptical aponeurosis, which reaches from the sixth cervical to the third thoracic vertebræ and forms, with that of the opposite muscle, a tendinous ellipse.
The rest of the muscle arises by numerous short tendinous fibers. It is possible to feel the muscles of the superior trapezius become active by holding a weight in one hand in front of the body and, with the other hand, touching the area between the shoulder and the neck. Images of the trapezius and the bones to which it attaches, with muscular attachments shown in red Motor function is supplied by the accessory nerve. Sensation, including pain and the sense of joint position, travel via the ventral rami of the third and fourth cervical nerves. Since it is a muscle of the upper limb, the trapezius is not innervated by dorsal rami despite being placed superficially in the back. Contraction of the trapezius muscle can have two effects: movement of the scapulae when the spinal origins are stable, movement of the spine when the scapulae are stable, its main function is to move the scapula. The upper and lower fibers tend to rotate the scapula around the Sternoclavicular articulation so that the acromion and inferior angles move up and the medial border moves down.
This rotation is in the opposite direction to that produced by the rhomboids. The middle fibers retract the scapula; the upper and lower trapezius fibers work in tandem with the serratus anterior to upwardly rotate the scapulae, such as during an overhead press. When activating together, the upper and lower fibers assist the middle fibers with scapular retraction/adduction; when the scapulae are stable a co-contraction of both sides can extend the neck. The upper portion of the trapezius can be developed by elevating the shoulders. Common exercises for this movement are any version of the clean the hang clean. Middle fibers are developed by pulling shoulder blades together; this adduction uses the upper/lower fibers. The lower part can be developed by drawing the shoulder blades downward while keeping the arms straight and stiff, it is used in throwing, with the deltoid muscle and rotator cuff. Many bodybuilders, including eight-time Mr. Olympia winner Ronnie Coleman, perform a maneuver known as a'trap slap' before attempting to lift heavy weights.
This technique involves a spotter slapping the lifter's upper back, with the desired effect of mentally preparing the recipient for their upcoming lift. Variants of the trap slap include the'lat slap', performed if the trapezius is inaccessible to the spotter. Due to not being healthily developed for some people, it can cause problems such as muscular tensions the descending part. In severe cases these might cause a cervical spine syndrome; this article incorporates text in the public domain from page 432 of the 20th edition of Gray's Anatomy Muscles/TrapeziusUpper at exrx.net Superficial Back Dissection Video showing trapezius
Phrenic nerve
The phrenic nerve is a nerve that originates in the neck and passes down between the lung and heart to reach the diaphragm. It takes its name from the Ancient Greek phren, it is important for breathing, as it passes motor information to the diaphragm and receives sensory information from it. There are a left and a right one; the phrenic nerve originates from the 4th cervical nerve, but receives contributions from the 5th and 3rd cervical nerves in humans. Thus, the phrenic nerve receives innervation from parts of both the cervical plexus and the brachial plexus of nerves; the phrenic nerves contain motor and sympathetic nerve fibers. These nerves provide the only motor supply to the diaphragm as well as sensation to the central tendon. In the thorax, each phrenic nerve supplies pericardium; the phrenic nerve descends obliquely with the internal jugular vein across the anterior scalene, deep to the prevertebral layer of deep cervical fascia and the transverse cervical and suprascapular arteries.
On the left, the phrenic nerve crosses anterior to the first part of the subclavian artery. On the right, it lies on the anterior scalene muscle and crosses anterior to the 2nd part of the subclavian artery. On both sides, the phrenic nerve runs posterior to the subclavian vein as it enters the thorax where it runs anterior to the root of the lung and between the fibrous pericardium and mediastinal face of the parietal pleura. Found in the posterior mediastinum, both phrenic nerves run from C3, C4, C5 along the anterior scalene muscle deep to the carotid sheath; the right phrenic nerve passes over the brachiocephalic artery, posterior to the subclavian vein, crosses the root of the right lung anteriorly and leaves the thorax by passing through the vena cava hiatus opening in the diaphragm at the level of T8. The right phrenic nerve passes over the right atrium; the left phrenic nerve passes over the pericardium of the left ventricle and pierces the diaphragm separately. The pericardiacophrenic arteries and veins travel with their respective phrenic nerves.
The phrenic nerve can be marked by a line connecting these two points: 1st point can be labelled 3.5 cm at the level of the thyroid cartilage from the midsagittal plane. 2nd point is at the medial end of the clavicle. The contribution of the 5th cervical nerve may stem from an accessory phrenic nerve. Phrenic nerve in its early course close to its origin, was giving a communicating branch to C5 root of brachial plexus; the phrenic nerve at the level of root of neck just before entering the thorax was placed in front of the subclavian vein. It is placed posterior in between subclavian vein and artery. Most it is a branch of the nerve to the subclavius and may contain numerous phrenic nerve fibers. If the accessory phrenic nerve is present, it lies lateral to the main nerve and descends posterior and inferior to the subclavian vein; the accessory phrenic nerve connects to the root of the neck. In canines the phrenic nerve arises from C5-C7 with occasional small contributions from C4. In the cat, horse, ox, small ruminant the phrenic nerve arises variably from C4-C7.
Both of these nerves supply motor fibers to the diaphragm and sensory fibers to the fibrous pericardium, mediastinal pleura, diaphragmatic peritoneum. Some sources describe the right phrenic nerve as innervating the gallbladder, other sources make no such mention. Pain arising from structures supplied by the phrenic nerve is "referred" to other somatic regions served by spinal nerves C3-C5. For example, a subphrenic abscess beneath the right diaphragm might cause a patient to feel pain in the right shoulder. Irritation of the phrenic nerve leads to the hiccup reflex. A hiccup is a spasmodic contraction of the diaphragm, which pulls air against the closed folds of the larynx; the phrenic nerve must be preserved. To confirm the identity of the phrenic nerve manipulate it to elicit a dartle response; the right phrenic nerve may be crushed by the vena cava clamp during liver transplantation. Severing the phrenic nerve, or a phrenectomy, will paralyse that half of the diaphragm. Diaphragm paralysis is best demonstrated by sonography.
Breathing will continue provided the other nerve is intact. The phrenic nerve arises from the neck and innervates the diaphragm, much lower. Hence, patients suffering spinal cord injuries below the neck are still able to breathe despite any paralysis of the lower limbs. Brachial plexus injuries can cause paralysis to various regions in the arm and hand depending on the severed nerves; the resulting palsy has been clinically treated using the phrenic nerve as a donor for neurotization of the musculocutaneous nerve and the median nerve. This treatment has a high success rate in partial to full restoration of the innervation to the damaged nerve. Furthermore, this procedure has resulted in restored function to nerves in the brachial plexus with minimal impact to respiratory function of the phrenic nerve; the instances where pulmonary vital capacity is reduced have been a result of use of the right phrenic as the donor for the neurotization whereas use of left phrenic nerve has not been linked to reduced pulmonary vital capacity.
Anatomy figure: 19:04-05 at Human Anatomy Online, SUNY Downstate Medical Center - "Left side of the mediastinum." Anatomy figure: 25:03-15 at Human Anatomy Online, SUNY Downstate Medical Center - "Diagram of the cervical plexus."
Anatomical terms of muscle
Muscles are described using unique anatomical terminology according to their actions and structure. There are three types of muscle tissue in the human body: skeletal and cardiac. Skeletal striated muscle, or "voluntary muscle" joins to bone with tendons. Skeletal muscle maintains posture. Smooth muscle tissue is found in parts of the body; the majority of this type of muscle tissue is found in the digestive and urinary systems where it acts by propelling forward food and feces in the former and urine in the latter. Other places smooth muscle can be found are within the uterus, where it helps facilitate birth, the eye, where the pupillary sphincter controls pupil size. Cardiac muscle is specific to the heart, it is involuntary in its movement, is additionally self-excitatory, contracting without outside stimuli. As well as anatomical terms of motion, which describe the motion made by a muscle, unique terminology is used to describe the action of a set of muscles. Agonist muscles and antagonist muscles refer to muscles that inhibit a movement.
Agonist muscles cause a movement to occur through their own activation. For example, the triceps brachii contracts, producing a shortening contraction, during the up phase of a push-up. During the down phase of a push-up, the same triceps brachii controls elbow flexion while producing a lengthening contraction, it is still the agonist, because while resisting gravity during relaxing, the triceps brachii continues to be the prime mover, or controller, of the joint action. Agonists are interchangeably referred to as "prime movers," since they are the muscles considered responsible for generating or controlling a specific movement. Another example is the dumbbell curl at the elbow; the "elbow flexor" group is the agonist. During the lowering phase the "elbow flexor" muscles lengthen, remaining the agonists because they are controlling the load and the movement. For both the lifting and lowering phase, the "elbow extensor" muscles are the antagonists, they shorten during the dumbbell lowering phase.
Here it is important to understand that it is common practice to give a name to a muscle group based on the joint action they produce during a shortening contraction. However, this naming convention does not mean; this term describes the function of skeletal muscles. Antagonist muscles are the muscles that produce an opposing joint torque to the agonist muscles; this torque can aid in controlling a motion. The opposing torque can slow movement down - in the case of a ballistic movement. For example, during a rapid discrete movement of the elbow, such as throwing a dart, the triceps muscles will be activated briefly and to accelerate the extension movement at the elbow, followed immediately by a "burst" of activation to the elbow flexor muscles that decelerates the elbow movement to arrive at a quick stop. To use an automotive analogy, this would be similar to pressing your gas pedal and immediately pressing the brake. Antagonism is not an intrinsic property of a particular muscle group. During slower joint actions that involve gravity, just as with the agonist muscle, the antagonist muscle can shorten and lengthen.
Using the example above of the triceps brachii during a push-up, the elbow flexor muscles are the antagonists at the elbow during both the up phase and down phase of the movement. During the dumbbell curl, the elbow extensors are the antagonists for both the lifting and lowering phases. Antagonist and agonist muscles occur in pairs, called antagonistic pairs; as one muscle contracts, the other relaxes. An example of an antagonistic pair is the triceps. "Reverse motions" need antagonistic pairs located in opposite sides of a joint or bone, including abductor-adductor pairs and flexor-extensor pairs. These consist of an extensor muscle, which "opens" the joint and a flexor muscle, which does the opposite by decreasing the angle between two bones. However, muscles don't always work this way. Sometimes during a joint action controlled by an agonist muscle, the antagonist will be activated, naturally; this occurs and is not considered to be a problem unless it is excessive or uncontrolled and disturbs the control of the joint action.
This serves to mechanically stiffen the joint. Not all muscles are paired in this way. An example of an exception is the deltoid. Synergist muscles help perform, the same set of joint motion as the agonists. Synergists muscles act on movable joints. Synergists are sometimes referred to as "neutralizers" because they help cancel out, or neutralize, extra motion from the agonists to make sure that the force generated works within the desired plane of motion. Muscle fibers can only contract up to 40% of their stretched length, thus the short fibers of pennate muscles are more suitable where power rather than range of contraction is required. This limitation in the range of contraction affects all muscles, those that act over several joints may be unable to shorten sufficiently to produce
