Thyroid Gland Anatomy
- The thyroid is one of {the} largest endocrine glands in {the} body. This gland is found in {the} neck inferior to (below) {the} thyroid cartilage (sometimes referred to as {the} Adam's apple in men) and at approximately {the} same level as {the} cricoid cartilage. The thyroid controls how quickly {the} body burns energy, makes proteins, and controls how sensitive {the} body should be to other hormones.
- The thyroid participates in these processes by producing thyroid hormones, principally thyroxine (T4) and triiodothyronine (T3). These hormones regulate {the} rate of metabolism and affect {the} growth and rate of function of various other systems in {the} body. Iodine and tyrosine are used to form both T3 and T4. The thyroid also produces {the} hormone calcitonin, which plays a role in calcium homeostasis.
- The thyroid is controlled by {the} hypothalamus and pituitary. The gland gets its name from {the} Greek word for "shield", after {the} shape of {the} related thyroid cartilage. Hyperthyroidism (overactive thyroid) and hypothyroidism (underactive thyroid) are {the} most common problems of {the} thyroid gland.
- The thyroid gland is a butterfly-shaped organ and is composed of two cone-like lobes or wings: lobus dexter (right lobe) and lobus sinister (left lobe), connected with {the} isthmus. The organ is situated on {the} anterior side of {the} neck, lying against and around {the} larynx and trachea, reaching posteriorly {the} oesophagus and carotid sheath. It starts cranially at {the} oblique line on {the} thyroid cartilage (just below {the} laryngeal prominence or Adam's apple) and extends inferiorly to {the} fourth or fifth tracheal ring. It is difficult to demarcate {the} gland's upper and lower border with vertebral levels because it moves position in relation to these during swallowing.
- The thyroid gland is covered by a fibrous sheath, {the} capsula glandulae thyroidea, composed of an internal and external layer. The external layer is anteriorly continuous with {the} lamina pretrachealis fasciae cervicalis and posteriorolaterally continuous with {the} carotid sheath. The gland is covered anteriorly with infrahyoid muscles and laterally with {the} sternocleidomastoid muscle. Posteriorly, {the} gland is fixed to {the} cricoid and tracheal cartilage and cricopharyngeus muscle by a thickening of {the} fascia to form {the} posterior suspensory ligament of Berry[In variable extent, Lalouette's Pyramid, a pyramidal extension of {the} thyroid lobe, is present at {the} most anterior side of {the} lobe. In this region {the} recurrent laryngeal nerve and {the} inferior thyroid artery pass next to or in {the} ligament and tubercle. Between {the} two layers of {the} capsule and on {the} posterior side of {the} lobes there are on each side two parathyroid glands.
- The thyroid isthmus is variable in presence and size, and can encompass a cranially extending pyramid lobe (lobus pyramidalis or processus pyramidalis), remnant of {the} thyroglossal duct. The thyroid is one of {the} larger endocrine glands, weighing 2-3 grams in neonates and 18-60 grams in adults, and is increased in pregnancy.
- The thyroid is supplied with arterial blood from {the} superior thyroid artery, a branch of {the} external carotid artery, and {the} inferior thyroid artery, a branch of {the} thyrocervical trunk, and may be by {the} thyroid ima artery, branching directly from {the} aortic arch. The venous blood is drained via superior thyroid veins, draining in {the} internal jugular vein, and via inferior thyroid veins, draining via {the} plexus thyroideus impar in {the} left brachiocephalic vein. Lymphatic drainage passes often {the} lateral deep cervical lymph nodes and {the} pre- and parathracheal lymph nodes. The gland is supplied by sympathetic nerve input from {the} superior cervical ganglion and {the} cervicothoracic ganglion of {the} sympathetic trunkand by parasympathetic nerve input from {the} superior laryngeal nerve and {the} recurrent laryngeal nerve.
Graves' disease is an autoimmune disease. It most commonly affects {the} thyroid, causing it to grow to twice its size or more (goiter), be overactive, with related hyperthyroid symptoms such as increased heartbeat, muscle weakness, disturbed sleep, and irritability. It can also affect {the} eyes, causing bulging eyes (exophthalmos). It affects other systems of {the} body, including {the} skin and reproductive organs. It affects up to 2% of {the} female population, often appears after childbirth, and has a female:male incidence of 5:1 to 10:1. It has a strong hereditary component; when one identical twin has Graves' disease, {the} other twin will have it 25% of {the} time. Smoking and exposure to second-hand smoke is associated with {the} eye manifestations but not {the} thyroid manifestations. Diagnosis is usually made on {the} basis of symptoms, although thyroid hormone tests may possibly be useful, particularly to monitor treatment.
Hypothyroidism is {the} disease state in humans and in animals caused by insufficient production of thyroid hormone by {the} thyroid gland. Cretinism is a form of hypothyroidism found in infants
Visit our website
Procedures
- Home
- Anophthalmos
- Blepharoplasty
- Blepharospasm
- Brow Lift
- Congenital
- Dry Eye
- Eyelid Laxity
- Face
- Infections
- Inflammation
- Lacrimal System
- Lagophthalmos
- Latisse
- Locate an MD
- Orbital Tumors
- Ptosis
- Skin Rejuvenation
- Skin Tumors
- Symblepharon
- Thyroid
- Trauma