Thyroid adrenal.bds

Thyroid and Suprarenal Gland

Dr Sandip Shah Dept of Anatomy

BPKIHS

Thyroid Gland

Lower part of the front & sides of the neck.

Weight-25gm

Capsules—True capsule & false capsule

� IMPORTANCE

Location & Extent

-C5-T1, embracing the upper part of

the trachea.

-Lobe =the middle of the thyroid

cartilage to 4th -5th tracheal

ring. ring.

-Isthmus = 2nd -4th tracheal ring.

� Suspensory Ligament of Berry

� Pyramidal lobe-Levator of TG

Functions

A) Regulates the BMR

B) Stimulates somatic & psychic

growth.

C) Plays an important role in

calcium metabolism.

Development

� Pharyngeal outgrowths that migrate caudally to their final position as

development continues.

� Foramen caecum of the tongue indicates the site of origin and the

thyroglossal duct marks the path of migration of the thyroid gland to its

final adult location. final adult location.

� Thyroglossal duct usually disappears early in development, but remnants

may persist as a cyst or as a connection to the foramen caecum (i.e. a

fistula).

� There may also be remains of the thyroid gland: associated with the

tongue (a lingual thyroid); along the path of migration; or, upward from

the gland along the path of the thyroglossal duct (a pyramidal lobe).

Lobes -Conical -- Apex, Base,

3 surfaces( Lat, Medial & Posterolateral),

2 borders( Ant & Post)

• Ant border—Ant. Branch of the Sup thyroid art.

• Post border—Inf. Thyroid art, parathyroid glands.

Relation• Apex—Upwards & Laterally, attached

to the sternothyroid to the oblique

line of the thyroid cartilage.

• Base– 4th -5th tracheal ring.

• Lateral –Sternothyroid, Sup. Belly of

Omohyoid, Sternohyiod, Ant. Border Omohyoid, Sternohyiod, Ant. Border

of SCM muscle.

• Medial – 2 tubes( Trachea &

Oesophagus), 2 muscles(

Inf.constrictor,Cricothyroid), 2 nerves(

External & Recurrent laryngeal)

• Posterolateral—Carotid sheath

Blood supply Sup. & Inf thyroid artery

� SIGNIFICANCE

� STA- First branch of ECA

� Descent passing along the lateral

margin of the thyrohyoid muscle,

to reach the superior pole of the

lateral lobe of the gland where it

divides into anterior and

posterior glandular branches:

• Inferior thyroid artery is a branch of

the thyrocervical trunk, which arises

from the first part of the subclavian

artery .

• It ascends along the medial edge of

the anterior scalene muscle, passes the anterior scalene muscle, passes

posteriorly to the carotid sheath, and

reaches the inferior pole of the

lateral lobe of the thyroid gland.

• Two br- inferior and ascending

(parathyroid)

Thyroid ima artery

Occasionally(3%), a small thyroid ima artery

Arises from the brachiocephalic trunk or the arch of the aorta

Arises from the brachiocephalic trunk or the arch of the aorta

Ascends on the anterior surface of the trachea to supply the

thyroid gland.

-Sup, middle ,inf thyroid vein ,4th Kocher

vein

-Nerve supply—mainly from the middle

cervical ganglion & partly from superior &

inferior cervical ganglion .

-Lymphatic – Deep cevical node.

Microanatomy

• Unique among the human endocrine glands in that it stores large

amounts of hormone in an inactive form within extracellular

compartments in the centre of follicles; in contrast, other endocrine

glands store only small quantities of hormones in intracellular sites.

• Thyroid follicles store thyroglobulin, an iodinated glycoprotein, the storage

form of thyroxine (T4) and tri-iodothyronine (T3).

• The follicles are lined by epithelial

cells which are initially responsible for the synthesis of the glycoprotein component of thyroglobulin and for the conversion of iodide to iodine, the iodine linking to the glycoprotein in the follicle lumen.

• When active thyroid hormone is required, the same thyroid epithelial cells remove some of the stored required, the same thyroid epithelial cells remove some of the stored thyroid colloid and detach T3 and T4, which then pass through the cell into an adjacent capillary.

• When inactive, thyroid epithelial cells are simple flat or cuboidalcells, but when actively synthesisingor secreting thyroid hormone they are tall and columnar.

Thyroid C cell• Clear or light cell

• Ultrastructural characteristics of neuroendocrine cells,

the C cell or parafollicular cell C, is found in the thyroid

gland as individual scattered cells in the follicle lining, or

as small clumps in the interstices between follicles.

• These cells secrete calcitonin, which is a physiological

antagonist to parathormone and therefore lowers blood

calcium levels by suppressing the osteoclastic resorption

of bone.

Thyroid gland pathology Diffusely or focally enlarged(numerous causes)

Thyroid gland may under- or oversecrete the hormone thyroxine.

• One of the commonest disorders of the thyroid gland is a multinodular goiter, which is a diffuse irregular enlargement of the thyroid gland with areas of thyroid hypertrophy and colloid cyst formation. Most patients are euthyroid (i.e. have normal serum thyroxine levels).

• Immunological diseases may affect the thyroid gland and may overstimulate it to produce excessive thyroxine.

• These diseases may be associated with other extrathyroid manifestations, which include exophthalmos, pretibial myxedema, and nail changes.

• Other causes of diffuse thyroid stimulation include viral thyroiditis.

• Some diseases may cause atrophy of the thyroid gland, leading to undersecretionof thyroxine (myxedema).

Ultrasound easily demonstrates their nature and position, and

treatment is by surgical excision and Nuclear Scan

Thyroid gland

� Thyroidectomy - For benign diseases such as multinodular goiter.

� possibility of damaging other structures when carrying out a thyroidectomy, namely

• The parathyroid glands (which may be excised en masse with the thyroid gland), thyroid gland),

• The recurrent laryngeal nerve,

• The sympathetic trunk, and

• Rarely, the nerves of the carotid sheath.

• Pair of important endocrine

glands situated on the

posterior abdominal wall

• Over the upper pole of the

kidneys behind the peritoneum kidneys behind the peritoneum

• lies in the Epigastrium, in front

of the crus of the diaphragm,

opposite the vertebral end of

the 11th intercostal space and

the 12th rib.

• 50 mm in height, 30mm in breadth, 10 mm in thickness, 5

gm in weight.

• They are made up of 2 parts

a) An outer cortex- mesodermal origin which secrets a

number of steriod hormones. number of steriod hormones.

b) An inner medulla- neural crest origin, which is made up of

chromaffin cells and secrets adrenalin & noradrenallin

(catecholamines)

Right Left

Shape Pyramidal Semilunar

Parts Apex-bare area of liver

Base-upper pole of right liver

Upper end-close to spleen

Lower end – hilum left

vein

Anterior surface IVC, Bare area of liver Cardiac end of

stomach,pancreas with

splenic artery

Posterior

surface

Rt crus of diaphragm,rt kidney Left crus of diaphragm,left

kidney

Anterior border Hilum-right hilum --------

Medial border Coeliac ganglia Coeliac ganglia

Lateral border Liver stomach

Arterial supply

1) Superior suprarenal

artery-Inferior

phrenic artery

2) Middle suprarenal 2) Middle suprarenal

artery- Abdominal

aorta

3) Inferior suprarenal

artery-Renal artey

• The vascular system of the cortex C

consists of an anastomosing

network of capillary sinusoids

supplied by branches of the

subcapsular plexus, known as short

cortical arteries.

• The medulla is supplied by long

cortical arteries which descend

from the subcapsular plexus

through the cortex into the medulla

where they ramify into a rich

network of dilated capillaries

surrounding the medullary

secretory cells.

Venous drainage

1) Right suprarenal vein-

Ivc

2) Lt suprarenal vein –Lt

renal vein

Lymphatic-lateral Aortic

node

Nerve- medulla-

myelinated

preganglionic

sympathetic fiber

• Adrenal cortex has a similar embryological origin to the gonads and, like them, secretes a variety of steroid hormones all structurally related to their common precursor, cholesterol. The adrenal steroids may be divided into three functional classes, mineralocorticoids, glucocorticoids and sex hormones.

� The mineralocorticoids are concerned with electrolyte and fluid homeostasis.

� The glucocorticoids have a wide range of effects on carbohydrate, protein and lipid metabolism.

� Small quantities of sex hormones are secreted by the adrenal cortex and supplement gonadal sex hormone secretion.

• Adrenal medulla secretes the catecholamine hormones, adrenaline(epinephrine) and noradrenaline (norepinephrine).

Histology

• The zona glomerulosaG(1/5th) is composed of cells arranged in irregular ovoid clusters separated by delicate fibrous trabeculae Tcontinuous with the fibrocollagenous capsule Cap; both the trabeculae and inner capsule contain prominent capillaries.

• The cells have round nuclei • The cells have round nuclei and less cytoplasm than the cells in the adjacent zonafasciculata.

• The cytoplasm contains plentiful smooth endoplasmic reticulum and numerous mitochondria, but with only scanty lipid droplets.

• The zona fasciculata(3/5 th) is the

middle and broadest of the three

cortical zones.

• It consists of narrow columns and

cords of cells, often only one cell

thick, separated by fine strands of

thick, separated by fine strands of

collagen and wide bore capillaries.

• The cell cytoplasm is abundant and

pale staining due to the large

number of lipid droplets present;

mitochondria and smooth

endoplasmic reticulum are also

abundant.

• The zona reticularis(1/5th) R is the thin

innermost layer of the adrenal cortex, and

lies next to the adrenal medulla M.

• It consists of an irregular network of

branching cords and clusters of glandular

cells separated by numerous wide diameter

capillaries.

• The zona reticularis cells are much smaller

than those of the adjacent zona fasciculata

with less cytoplasm.

• The cytoplasm is darker staining because it

contains considerably fewer lipid droplets.

Brown lipofuscin pigment is sometimes seen

in the cells of this layer.

• The zona reticularis secretes small quantities

of androgens and glucocorticoids.

Adrenal medulla• The adrenal medulla secretes

the amines adrenaline (epinephrine) and noradrenaline(norepinephrine) under the control of the sympathetic nervous system.

• When stained with the

standard H [amp ] E method the adrenal medulla is the adrenal medulla is composed of clusters of cells with granular, faintly basophilic cytoplasm, with numerous capillaries in their fine supporting stroma.

• Venous channels V draining

blood from the sinusoids of the cortex pass through the medulla towards the central medullary vein.

APPLIED ANATOMY

• The excess hormone may be produced by a benign tumour (adrenal cortical

adenoma) or a malignant tumour (adrenal cortical carcinoma), or by diffuse

hyperplasia of the adrenal cortex.

• Destruction of both adrenals (for example, by autoimmune adrenalitis or, in • Destruction of both adrenals (for example, by autoimmune adrenalitis or, in

former years, by tuberculosis) leads to failure of secretion of all adrenal cortical

hormones (hypoadrenalism), leading to the clinical syndrome called Addison's

disease (weakness, tiredness, skin pigmentation, postural hypotension,

hypovolaemia and low blood sodium).

• More common is hyperadrenalism where there is excess secretion of one or more

of the cortical hormones, mainly glucocorticoids (producing Cushing's syndrome-

obesity,hirustism diabetes and hypogonadism) or mineralocorticoids (producing

Conn's syndrome) or virilism(excessive androgens may cause masculinization) or

male excessive estrogen cause feminisation—breast enlargement

• Children-excessive sex hormones cause adrenogenital syndrome—• Children-excessive sex hormones cause adrenogenital syndrome—

pseudohermaphroidism

• Tumor of medulla-Pheochromocytoma---HTN,Excessive sweating,pallor of skin

THANK YOU