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The neck is the part of the body on many
vertebrate Vertebrates () comprise all animal Animals are multicellular, eukaryotic organisms in the biological kingdom Animalia. With few exceptions, animals consume organic material, breathe oxygen, are able to move, can reproduce sexually ...
s that connects the
head A head is the part of an organism which usually includes the ears, brain, forehead, cheeks, chin, eyes, nose, and mouth, each of which aid in various sensory functions such as visual perception, sight, hearing, olfaction, smell, and taste. Some ...
with the
torso The torso or trunk is an anatomical terminology, anatomical term for the central part, or the core (anatomy), core, of the body (biology), body of many animals (including humans), from which the head, neck, limb (anatomy), limbs, tail and other a ...
. The neck supports the weight of the head and protects the nerves that carry sensory and motor information from the
brain A brain is an organ (biology), organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It is located in the head, usually close to the sensory organs for senses such as Visual perception, vision. I ...
down to the rest of the body. In addition, the neck is highly flexible and allows the head to turn and flex in all directions. The structures of the human neck are anatomically grouped into four compartments; vertebral, visceral and two vascular compartments. Within these compartments, the neck houses the
cervical vertebrae In tetrapods, cervical vertebrae (singular: vertebra) are the vertebrae of the neck, immediately below the skull. Truncal vertebrae (divided into thoracic vertebrae, thoracic and lumbar vertebrae in mammals) lie caudal (toward the tail) of cervic ...
and cervical part of the
spinal cord The spinal cord is a long, thin, tubular structure made up of nervous tissue, which extends from the medulla oblongata in the brainstem to the lumbar region of the vertebral column (backbone). The backbone encloses the central canal of the spinal ...
, upper parts of the
respiratory The respiratory system (also respiratory apparatus, ventilatory system) is a biological system consisting of specific organs and structures used for gas exchange in animals and plants. The anatomy and physiology that make this happen varies grea ...
and digestive tracts,
endocrine gland Endocrine glands are ductless gland In animals, a gland is a group of cells in an animal's body that synthesizes substances (such as hormones) for release into the bloodstream (Endocrine system, endocrine gland) or into cavities inside the b ...
s,
nerve A nerve is an enclosed, cable-like bundle of nerve fibers (called axons) in the peripheral nervous system. A nerve transmits electrical impulses. It is the basic unit of the peripheral nervous system. A nerve provides a common pathway for the E ...
s,
arteries An artery (plural arteries) () is a blood vessel in humans and most animals that takes blood away from the heart to one or more parts of the body (tissues, lungs, brain etc.). Most arteries carry oxygenated blood; the two exceptions are the pul ...
and
vein Veins are blood vessels in humans and most other animals that carry blood towards the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are the pulmonary and umbilical veins, both of which carry oxygen ...
s. Muscles of the neck are described separately from the compartments. They bound the neck triangles. In
anatomy Anatomy () is the branch of biology concerned with the study of the structure of organisms and their parts. Anatomy is a branch of natural science that deals with the structural organization of living things. It is an old science, having its ...
, the neck is also called by its Latin names, or , although when used alone, in context, the word ''cervix'' more often refers to the
uterine cervix The cervix or cervix uteri (Latin, 'neck of the uterus') is the lower part of the uterus (womb) in the human female reproductive system. The cervix is usually 2 to 3 cm long (~1 inch) and roughly cylindrical in shape, which changes during ...
, the neck of the
uterus The uterus (from Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around p ...
. Thus the adjective ''cervical'' may refer either to the neck (as in ''
cervical vertebrae In tetrapods, cervical vertebrae (singular: vertebra) are the vertebrae of the neck, immediately below the skull. Truncal vertebrae (divided into thoracic vertebrae, thoracic and lumbar vertebrae in mammals) lie caudal (toward the tail) of cervic ...
'' or ''
cervical lymph nodes Cervical lymph nodes are lymph nodes found in the neck. Of the 800 lymph nodes in the human body, 300 are in the neck. Cervical lymph nodes are subject to a number of different pathological conditions including neoplasm, tumours, infection and i ...
'') or to the uterine cervix (as in ''
cervical cap The cervical cap is a form of barrier contraception Birth control, also known as contraception, anticonception, and fertility control, is the use of methods or devices to prevent unwanted pregnancy. Birth control has been used since anci ...
'' or ''
cervical cancer Cervical cancer is a cancer arising from the cervix. It is due to the abnormal growth of Cell (biology), cells that have the ability to invade or spread to other parts of the body. Early on, typically no symptoms are seen. Later symptoms may inc ...
'').


Structure


Compartments

The neck structures are distributed within four compartments: * Vertebral compartment contains the
cervical vertebrae In tetrapods, cervical vertebrae (singular: vertebra) are the vertebrae of the neck, immediately below the skull. Truncal vertebrae (divided into thoracic vertebrae, thoracic and lumbar vertebrae in mammals) lie caudal (toward the tail) of cervic ...
with cartilaginous discs between each
vertebral body The spinal column, a defining synapomorphy shared by nearly all vertebrates,Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristic i ...
. The alignment of the vertebrae defines the shape of the human neck. As the vertebrae bound the spinal canal, the cervical portion of the spinal cord is also found within the neck. * Visceral compartment accommodates the
trachea The trachea, also known as the windpipe, is a Cartilage, cartilaginous tube that connects the larynx to the bronchi of the lungs, allowing the passage of air, and so is present in almost all air-breathing animals with lungs. The trachea extends ...
,
larynx The larynx (), commonly called the voice box, is an organ (anatomy), organ in the top of the neck involved in breathing, producing sound and protecting the trachea against food aspiration. The opening of larynx into pharynx known as the laryngeal ...
,
pharynx The pharynx (plural: pharynges) is the part of the throat behind the mouth and nasal cavity The nasal cavity is a large, air-filled space above and behind the human nose, nose in the middle of the face. The nasal septum divides the cavity int ...
,
thyroid The thyroid, or thyroid gland, is an endocrine gland in vertebrates. In humans it is in the neck and consists of two connected lobe (anatomy), lobes. The lower two thirds of the lobes are connected by a thin band of Connective tissue, tissue cal ...
and
parathyroid gland Parathyroid glands are small endocrine glands in the neck of humans and other tetrapods. Humans usually have four parathyroid glands, located on the back of the thyroid gland in variable locations. The parathyroid gland produces and secretes ...
s. * Vascular compartment is paired and consists of the two
carotid sheath The carotid sheath is an anatomical term for the fibrous connective tissue that surrounds the vascular compartment of the neck. It is part of the deep cervical fascia of the neck, below the superficial cervical fascia meaning the subcutaneous adipo ...
s found on each side of the trachea. Each carotid sheath contains the
vagus nerve The vagus nerve, also known as the tenth cranial nerve, cranial nerve X, or simply CN X, is a cranial nerve that interfaces with the parasympathetic control of the heart, lungs, and digestive tract. It comprises two nerves—the left and right v ...
, common carotid artery and
internal jugular vein The internal jugular vein is a paired jugular vein that collects blood from the brain and the superficial parts of the face and neck. This vein runs in the carotid sheath with the common carotid artery and vagus nerve. It begins in the posterio ...
. Besides the listed structures, the neck contains
cervical lymph nodes Cervical lymph nodes are lymph nodes found in the neck. Of the 800 lymph nodes in the human body, 300 are in the neck. Cervical lymph nodes are subject to a number of different pathological conditions including neoplasm, tumours, infection and i ...
which surround the blood vessels.


Muscles and triangles

Muscles of the neck attach to the
skull The skull is a bone protective Cranial cavity, cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible ...
,
hyoid bone The hyoid bone (lingual bone or tongue-bone) () is a horseshoe-shaped bone A bone is a rigid organ Organ may refer to: Biology * Organ (biology), a part of an organism Musical instruments * Organ (music), a family of keyboard musical ...
,
clavicle The clavicle, or collarbone, is a slender, S-shaped long bone approximately 6 inches (15 cm) long that serves as a strut between the scapula, shoulder blade and the sternum (breastbone). There are two clavicles, one on the left and one on ...
s and the
sternum The sternum or breastbone is a long flat bone located in the central part of the chest. It connects to the ribs via cartilage and forms the front of the rib cage, thus helping to protect the heart, human lung, lungs, and major blood vessels from ...
. They bound the two major neck triangles; anterior and posterior. Anterior triangle is defined by the anterior border of the
sternocleidomastoid muscle The sternocleidomastoid muscle is one of the largest and most superficial cervical muscles. The primary actions of the muscle are rotation of the head to the opposite side and Anatomical terms of motion#Flexion and extension, flexion of the neck. T ...
, inferior edge of the
mandible In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower tooth, teeth in place. The mandible sits beneath the maxilla. It is the only movabl ...
and the midline of the neck. It contains the
stylohyoid The stylohyoid muscle is a Gracility, slender muscle, lying anterior and Anatomical terms of location#Superior and inferior, superior of the posterior belly of the digastric muscle. It is one of the suprahyoid muscles. It shares this muscle's inn ...
,
digastric The digastric muscle (also digastricus) (named ''digastric'' as it has two 'bellies') is a small muscle located under the jaw. The term "digastric muscle" refers to this specific muscle. However, other muscles that have two separate muscle bellie ...
, mylohyoid,
geniohyoid The geniohyoid muscle is a narrow muscle Skeletal muscles (commonly referred to as muscles) are Organ (biology), organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skelet ...
,
omohyoid The omohyoid muscle is a muscle that depresses the hyoid. It is located in the front of the neck, and consists of two bellies separated by an intermediate tendon. The omohyoid muscle is proximally attached to the scapula and distally attached to th ...
,
sternohyoid The sternohyoid muscle is a thin, narrow muscle attaching the hyoid bone to the Human sternum, sternum. It is one of the paired strap muscles of the infrahyoid muscles. It is supplied by the ansa cervicalis. It depresses the hyoid bone. Structure ...
,
thyrohyoid The thyrohyoid muscle is a small skeletal muscle on the neck. It originates from the lamina of the thyroid cartilage, and inserts into the greater cornu of the hyoid bone. It is supplied by the hypoglossal nerve, and a branch of the Ventral ramus ...
and
sternothyroid muscle The sternothyroid muscle, or sternothyroideus, is an Infrahyoid muscles, infrahyoid muscle in the neck. It acts to depress the hyoid bone. It is below the sternohyoid muscle. It is shorter and wider than the sternohyoid. Structure The sternothyr ...
s. These muscles are grouped as the suprahyoid and
infrahyoid muscles The infrahyoid muscles, or strap muscles, are a group of four pairs of muscle Skeletal muscles (commonly referred to as muscles) are Organ (biology), organs of the vertebrate muscular system and typically are attached by tendons to bones of a ...
depending on if they are located superiorly or inferiorly to the hyoid bone. The suprahyoid muscles (stylohyoid, digastric, mylohyoid, geniohyoid) elevate the hyoid bone, while the infrahyoid muscles (omohyoid, sternohyoid, thyrohyoid, sternothyroid) depress it. Acting synchronously, both groups facilitate
speech Speech is a human vocal communication using language. Each language uses Phonetics, phonetic combinations of vowel and consonant sounds that form the sound of its words (that is, all English words sound different from all French words, even if ...
and
swallowing Swallowing, sometimes called deglutition in scientific contexts, is the process in the human or animal body that allows for a substance to pass from the mouth, to the pharynx, and into the esophagus, while shutting the epiglottis. Swallowing is ...
. Posterior triangle is bordered by the posterior border of the sternocleidomastoid muscle, anterior border of the
trapezius muscle The trapezius is a large paired trapezoid-shaped surface muscle that extends longitudinally from the occipital bone to the lower thoracic vertebrae of the human spine, spine and laterally to the spine of the scapula. It moves the scapula and ...
and the superior edge of the middle third of the clavicle. This triangle contains the sternocleidomastoid, trapezius,
splenius capitis The splenius capitis () () is a broad, straplike muscle in the back of the neck. It pulls on the base of the skull The base of skull, also known as the cranial base or the cranial floor, is the most Anatomical terms of location#Superior and infe ...
,
levator scapulae The levator scapulae is a slender skeletal muscle Skeletal muscles (commonly referred to as muscles) are Organ (biology), organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of ...
, omohyoid, anterior, middle and posterior
scalene muscles The scalene muscles are a group of three pairs of muscle Skeletal muscles (commonly referred to as muscles) are Organ (biology), organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscl ...
.


Nerve supply

Sensation to the front areas of the neck comes from the roots of the
spinal nerve A spinal nerve is a mixed nerve, which carries motor, sensory, and autonomic signals between the spinal cord and the body. In the human body there are 31 pairs of spinal nerves, one on each side of the vertebral column. These are grouped into the ...
s C2-C4, and at the back of the neck from the roots of C4-C5. In addition to nerves coming from and within the human spine, the
accessory nerve The accessory nerve, also known as the eleventh cranial nerve, cranial nerve XI, or simply CN XI, is a cranial nerve that supplies the sternocleidomastoid and trapezius muscles. It is classified as the eleventh of twelve pairs of cranial nerves ...
and vagus nerve travel down the neck.


Blood supply and vessels

Arteries which supply the neck are
common carotid arteries In anatomy, the left and right common carotid arteries (carotids) (Entry "carotid"
in
internal and
external carotid arteries The external carotid artery is a major artery An artery (plural arteries) () is a blood vessel in humans and most animals that takes blood away from the heart to one or more parts of the body (tissues, lungs, brain etc.). Most arteries carry ...
.


Surface anatomy

The
thyroid cartilage The thyroid cartilage is the largest of the nine cartilages that make up the ''laryngeal skeleton'', the cartilage structure in and around the Vertebrate trachea, trachea that contains the larynx. It does not completely encircle the larynx (only th ...
of the larynx forms a bulge in the midline of the neck called the
Adam's apple The Adam's apple or laryngeal prominence is the protrusion in the human neck formed by the angle of the thyroid cartilage surrounding the larynx, typically visible in men, less frequently in women. Structure The topographic structure which is e ...
. The Adam's apple is usually more prominent in men. Inferior to the Adam's apple is the
cricoid cartilage The cricoid cartilage , or simply cricoid (from the Greek ''krikoeides'' meaning "ring-shaped") or cricoid ring, is the only complete ring of cartilage around the Vertebrate trachea, trachea. It forms the back part of the larynx, voice box and fun ...
. The trachea is traceable at the midline, extending between the cricoid cartilage and
suprasternal notch The suprasternal notch, also known as the fossa jugularis sternalis, jugular notch, or Plender gap, is a large, visible dip in between the neck in humans, between the clavicles, and above the manubrium of the sternum. Structure The suprasternal ...
. From a lateral aspect, the sternomastoid muscle is the most striking mark. It separates the anterior triangle of the neck from the posterior. The upper part of the anterior triangle contains the
submandibular gland The paired submandibular glands (historically known as submaxillary glands) are major salivary glands located beneath the floor of mouth, floor of the mouth. They each weigh about 15 grams and contribute some 60–67% of unstimulated saliva secret ...
s, which lie just below the posterior half of the mandible. The line of the common and the external carotid arteries can be marked by joining the sterno-clavicular articulation to the angle of the jaw. Neck lines can appear at any age of adulthood as a result of sun damage, for example, or of
ageing Ageing ( BE) or aging ( AE) is the process of becoming older. The term refers mainly to humans, many other animals, and fungi, whereas for example, bacteria, perennial plants and some simple animals are potentially biologically immortal. I ...
where skin loses its elasticity and can
wrinkle A wrinkle, also known as a rhytid, is a fold, ridge or crease in an otherwise smooth surface, such as on skin or fabric. Skin fold, Skin wrinkles typically appear as a result of ageing processes such as glycation, habitual sleeping positions, ...
. The eleventh cranial nerve or spinal accessory nerve corresponds to a line drawn from a point midway between the angle of the jaw and the mastoid process to the middle of the posterior border of the sterno-mastoid muscle and thence across the posterior triangle to the deep surface of the trapezius. The external
jugular vein The jugular veins are veins that take Blood, deoxygenated blood from the head back to the heart via the superior vena cava. The internal jugular vein descends next to the internal carotid artery and continues posteriorly to the Sternocleidomast ...
can usually be seen through the skin; it runs in a line drawn from the angle of the jaw to the middle of the clavicle, and close to it are some small lymphatic glands. The anterior jugular vein is smaller, and runs down about half an inch from the middle line of the neck. The clavicle or collar-bone forms the lower limit of the neck, and laterally the outward slope of the neck to the shoulder is caused by the trapezius muscle.


Pain

Disorders of the neck are a common source of pain. The neck has a great deal of functionality but is also subject to a lot of stress. Common sources of
neck pain Neck pain, also known as cervicalgia, is a common problem, with two-thirds of the population having neck pain Pain is a distressing feeling often caused by intense or damaging stimuli. The International Association for the Study of Pain define ...
(and related pain syndromes, such as pain that radiates down the arm) include (and are strictly limited to): * Whiplash, strained a muscle or another soft tissue injury * Cervical
herniated disc Spinal disc herniation is an injury An injury is any physiological damage to living tissue caused by immediate physical stress. An injury can occur intentionally or Accident, unintentionally and may be caused by blunt trauma, penetrating tra ...
* Cervical spinal stenosis *
Osteoarthritis Osteoarthritis (OA) is a type of degenerative joint disease that results from breakdown of articular cartilage, joint cartilage and underlying bone which affects 1 in 7 adults in the United States. It is believed to be the fourth leading cause of ...
* Vascular sources of pain, like arterial dissections or internal jugular vein
thrombosis Thrombosis (from Ancient Greek "clotting") is the formation of a blood clot inside a blood vessel, obstructing the flow of blood through the circulatory system. When a blood vessel (a vein or an artery) is injured, the body uses platele ...
* Cervical adenitis


Circumference

Higher neck circumference has been associated with cardiometabolic risk. Upper-body fat distribution is a worse prognostic compared to lower-body fat distribution for diseases such as
type 2 diabetes mellitus Type 2 diabetes, formerly known as adult-onset diabetes, is a form of diabetes mellitus Diabetes, also known as diabetes mellitus, is a group of metabolic disorders characterized by a hyperglycemia, high blood sugar level (hyperglycemia) ove ...
or ischemic cardiopathy. Neck circumference has been associated with the risk of being mechanically ventilated in
COVID-19 Coronavirus disease 2019 (COVID-19) is a contagious disease caused by a virus, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The first known case was COVID-19 pandemic in Hubei, identified in Wuhan, China, in December ...
patients, with a 26% increased risk for each centimeter increase in neck circumference. Moreover, hospitalized COVID-19 patients with a "large neck phenotype" on admission had a more than double risk of death.


Other animals

The neck appears in some of the earliest of
tetrapod Tetrapods (; ) are four-limb (anatomy), limbed vertebrate animals constituting the superclass Tetrapoda (). It includes extant taxon, extant and extinct amphibians, sauropsids (reptiles, including dinosaurs and therefore birds) and synapsids (p ...
fossils, and the functionality provided has led to its being retained in all land vertebrates as well as marine-adapted tetrapods such as turtles, seals, and penguins. Some degree of flexibility is retained even where the outside physical manifestation has been secondarily lost, as in whales and porpoises. A morphologically functioning neck also appears among insects. Its absence in fish and aquatic arthropods is notable, as many have life stations similar to a terrestrial or tetrapod counterpart, or could otherwise make use of the added flexibility. The word "neck" is sometimes used as a convenience to refer to the region behind the head in some
snail A snail is, in loose terms, a shelled gastropod. The name is most often applied to land snails, terrestrial molluscs, terrestrial pulmonate gastropod molluscs. However, the common name ''snail'' is also used for most of the members of the m ...
s,
gastropod The gastropods (), commonly known as snails and slugs, belong to a large Taxonomy (biology), taxonomic class (taxonomy), class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater ...
mollusk Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant taxon, extant species of molluscs are recognized. The number of fossil sp ...
s, even though there is no clear distinction between this area, the head area, and the rest of the body.


See also

*
Throat In vertebrate anatomy, the throat is the front part of the neck, internally positioned in front of the vertebra, vertebrae. It contains the Human pharynx, pharynx and larynx. An important section of it is the epiglottis, separating the esophagus f ...
*
Nape The nape is the back of the neck. In technical anatomical/medical terminology, the nape is also called the nucha (from the Medieval Latin rendering of the Arabic , "spinal marrow"). The corresponding adjective is ''nuchal'', as in the term ''nu ...


References


External links


American Head and Neck Society

The Anatomy Wiz.
An Interactive Cross-Sectional Anatomy Atla
How To Increase neck size
, Top 5 best ways to Increase neck size. {{Authority control