Thyroid Gland |Parts| Relations| Blood supply|Microscopic structure | Development | Clinical Anatomy
97.4 هزار بار بازدید -
5 سال پیش
-
Features It is an endocrine
Features
It is an endocrine gland
Situated in the lower part of front & sides of neck
Regulates the basal metabolic rate
stimulates somatic & psychic growth
plays important role in calcium metabolism
uses natural iodine for the synthesis of hormone.
hormones stored within the follicles & used according to the needs of the body
It has - Right & left lobes, joined by isthmus
A third lobe (pyramidal Lobe) may project upwards from isthmus
Sometime a fibrous or fibre-muscular band ( levator glandulae thyroidae) descends from the body of hyoid bone to the isthmus or to the pyramidal lobe.
Situation
Lies against C5-C7 & T1vertebrae
embracing the upper part of trachea
Extent
Each lobe extends from middle of thyroid cartilage to 4th or 5th tracheal ring
Isthmus extends from 2nd to 4th tracheal ring
Dimensions lobe - 5 x 2.5 x2.5 cms isthmus - 1.2 x 1.2 cms Weight - 25gms
Larges in females than malesincreases in size during menstruation & pregnancy
Capsules of thyroid gland
1. True capsule - formed by peripheral condensation of connective tissue of the gland.
A dense capillary plexus is present deep to the true capsule.To avoid haemorrhage during operations, the thyroid is removed along with the true capsule.
It can be compared with the prostate in which the venous plexus lies between the two capsules of the gland; and, therefore, during prostatectomy both capsules are left behind
2. False capsule - formed by pre-tracheal layer of deep cervical fascia
It is thin along the posterior border of the lobes, but thick on the inner surface of the gland where it forms a suspensory ligament (of Berry), which connects the lobe to the cricoid cartilage
Lateral lobe
The lobes are conical in shape having: a. An apex
b. A base
c.Three Surfaces: Lateral, medial and posterolateral.
d.Two Borders: Anterior and posterior.
The apex is directed upwards and slightly laterally.It is limited superiorly by the attachment of the sternothyroid to the oblique line of thyroid cartilage.The apex is related to superior thyroid artery and external laryngeal nerveThe base is at level with the 4th or 5th tracheal ring.It is related to inferior thyroid artery and recurrent laryngeal nerve
The lateral or superficial surface is convex, and is covered by:
a. The sternohyoid
b. The superior belly of the omohyoid
c. The sternothyroid
d. The anterior border of the sternocleidomastoid
The medial surface is related to:a. Two tubes, trachea and oesophagusb. Two muscles, inferior constrictor and cricothyroid c. Two nerves, external laryngeal and recurrent laryngeal. The posterolateral or posterior surface is related to the carotid sheath and overlaps the common carotid artery
The anterior border is thin and is related to the anterior branch of superior thyroid artery.The posterior border is thick and rounded and separates the medial and posterior surfaces.It is related to: a. Inferior thyroid artery. b. Anastomosis between the posterior branch of superior and ascending branch of inferior thyroid arteries. c. Parathyroid glands. d. Thoracic duct only on the left side
The isthmus connects the lower parts of the two lobes. It has: a. Two surfaces: Anterior and posterior. b. Two borders: Superior and inferior.
The anterior surface is covered by:
a. The right and left sternothyroid and sternohyoid muscles. b. The anterior jugular veins.
c. Fascia and skin
The posterior surface is related to the second to fourth tracheal rings.
The upper border is related to anterior branches of the right and left superior thyroid arteries which anastomose here. The Lower border Inferior thyroid veins leave the gland at this border
Arterial Supply
The thyroid gland is supplied by the superior and inferior thyroid arteries.
1. The superior thyroid artery is the first anterior branch of the external carotid artery
It runs downwards and forwards in intimate relation to the external laryngeal nerve.
After giving branches to adjacent structures, it pierces the pretracheal fascia to reach the upper pole of the lobe where the nerve deviates medially. At the upper pole the artery divides into anterior and posterior branches.
The anterior branch descends on the anterior border of the lobe and continues along the upper border of the isthmus to anastomose with its fellow of the opposite side.
The posterior branch descends on the posterior border of the lobe and anastomoses with the ascending branch of inferior thyroid artery.
2. The inferior thyroid artery is a branch of thyrocervical trunk (which arises from the subclavian artery).
-------------------------------------------------------------------------------------------------------------
My website - https://human-anatomy-lessons.busines...
My Blog - https://human-anatomylessons.blogspot...
-----------------------------------------------------------------------------------------------------
Follow me in blogspot - https://human-anatomylessons.blogspot...
It is an endocrine gland
Situated in the lower part of front & sides of neck
Regulates the basal metabolic rate
stimulates somatic & psychic growth
plays important role in calcium metabolism
uses natural iodine for the synthesis of hormone.
hormones stored within the follicles & used according to the needs of the body
It has - Right & left lobes, joined by isthmus
A third lobe (pyramidal Lobe) may project upwards from isthmus
Sometime a fibrous or fibre-muscular band ( levator glandulae thyroidae) descends from the body of hyoid bone to the isthmus or to the pyramidal lobe.
Situation
Lies against C5-C7 & T1vertebrae
embracing the upper part of trachea
Extent
Each lobe extends from middle of thyroid cartilage to 4th or 5th tracheal ring
Isthmus extends from 2nd to 4th tracheal ring
Dimensions lobe - 5 x 2.5 x2.5 cms isthmus - 1.2 x 1.2 cms Weight - 25gms
Larges in females than malesincreases in size during menstruation & pregnancy
Capsules of thyroid gland
1. True capsule - formed by peripheral condensation of connective tissue of the gland.
A dense capillary plexus is present deep to the true capsule.To avoid haemorrhage during operations, the thyroid is removed along with the true capsule.
It can be compared with the prostate in which the venous plexus lies between the two capsules of the gland; and, therefore, during prostatectomy both capsules are left behind
2. False capsule - formed by pre-tracheal layer of deep cervical fascia
It is thin along the posterior border of the lobes, but thick on the inner surface of the gland where it forms a suspensory ligament (of Berry), which connects the lobe to the cricoid cartilage
Lateral lobe
The lobes are conical in shape having: a. An apex
b. A base
c.Three Surfaces: Lateral, medial and posterolateral.
d.Two Borders: Anterior and posterior.
The apex is directed upwards and slightly laterally.It is limited superiorly by the attachment of the sternothyroid to the oblique line of thyroid cartilage.The apex is related to superior thyroid artery and external laryngeal nerveThe base is at level with the 4th or 5th tracheal ring.It is related to inferior thyroid artery and recurrent laryngeal nerve
The lateral or superficial surface is convex, and is covered by:
a. The sternohyoid
b. The superior belly of the omohyoid
c. The sternothyroid
d. The anterior border of the sternocleidomastoid
The medial surface is related to:a. Two tubes, trachea and oesophagusb. Two muscles, inferior constrictor and cricothyroid c. Two nerves, external laryngeal and recurrent laryngeal. The posterolateral or posterior surface is related to the carotid sheath and overlaps the common carotid artery
The anterior border is thin and is related to the anterior branch of superior thyroid artery.The posterior border is thick and rounded and separates the medial and posterior surfaces.It is related to: a. Inferior thyroid artery. b. Anastomosis between the posterior branch of superior and ascending branch of inferior thyroid arteries. c. Parathyroid glands. d. Thoracic duct only on the left side
The isthmus connects the lower parts of the two lobes. It has: a. Two surfaces: Anterior and posterior. b. Two borders: Superior and inferior.
The anterior surface is covered by:
a. The right and left sternothyroid and sternohyoid muscles. b. The anterior jugular veins.
c. Fascia and skin
The posterior surface is related to the second to fourth tracheal rings.
The upper border is related to anterior branches of the right and left superior thyroid arteries which anastomose here. The Lower border Inferior thyroid veins leave the gland at this border
Arterial Supply
The thyroid gland is supplied by the superior and inferior thyroid arteries.
1. The superior thyroid artery is the first anterior branch of the external carotid artery
It runs downwards and forwards in intimate relation to the external laryngeal nerve.
After giving branches to adjacent structures, it pierces the pretracheal fascia to reach the upper pole of the lobe where the nerve deviates medially. At the upper pole the artery divides into anterior and posterior branches.
The anterior branch descends on the anterior border of the lobe and continues along the upper border of the isthmus to anastomose with its fellow of the opposite side.
The posterior branch descends on the posterior border of the lobe and anastomoses with the ascending branch of inferior thyroid artery.
2. The inferior thyroid artery is a branch of thyrocervical trunk (which arises from the subclavian artery).
-------------------------------------------------------------------------------------------------------------
My website - https://human-anatomy-lessons.busines...
My Blog - https://human-anatomylessons.blogspot...
-----------------------------------------------------------------------------------------------------
Follow me in blogspot - https://human-anatomylessons.blogspot...
5 سال پیش
در تاریخ 1398/08/26 منتشر شده
است.
97,421
بـار بازدید شده