thyroid anatomy and physiology
TRANSCRIPT
![Page 1: Thyroid anatomy and physiology](https://reader036.vdocuments.site/reader036/viewer/2022070520/58f9b127760da3da068bbdee/html5/thumbnails/1.jpg)
THYROID GLAND
DR SYED UBAIDAssociate professor of surgery
![Page 2: Thyroid anatomy and physiology](https://reader036.vdocuments.site/reader036/viewer/2022070520/58f9b127760da3da068bbdee/html5/thumbnails/2.jpg)
SURGICAL ANATOMY FROM GREEK thyreoeides= SHIELD SHAPE
![Page 3: Thyroid anatomy and physiology](https://reader036.vdocuments.site/reader036/viewer/2022070520/58f9b127760da3da068bbdee/html5/thumbnails/3.jpg)
Thyroid Gland, Anterior and Posterior Views
![Page 4: Thyroid anatomy and physiology](https://reader036.vdocuments.site/reader036/viewer/2022070520/58f9b127760da3da068bbdee/html5/thumbnails/4.jpg)
SURGICAL ANATOMY
• TWO LOBES JOINED BY ISTHMUS• PYRAMIDAL LOBE (80%)PROJECT UPWARDS
FROM ISTHMUS OR EITHER OF THE LOBES• A FIBROMUSCULAR BAND levator glandulae
thyroideae DESCEND FROM THE BODY OF THE HYOID BONE TO ISTHMUS OR TO PYRAMIDAL LOBE
![Page 5: Thyroid anatomy and physiology](https://reader036.vdocuments.site/reader036/viewer/2022070520/58f9b127760da3da068bbdee/html5/thumbnails/5.jpg)
![Page 6: Thyroid anatomy and physiology](https://reader036.vdocuments.site/reader036/viewer/2022070520/58f9b127760da3da068bbdee/html5/thumbnails/6.jpg)
SURGICAL ANATOMY
![Page 7: Thyroid anatomy and physiology](https://reader036.vdocuments.site/reader036/viewer/2022070520/58f9b127760da3da068bbdee/html5/thumbnails/7.jpg)
SURGICAL ANATOMY
• GLAND LIES AGAINST C5,6,7 &T1 VERTEBRAE• EACH LOBE EXTENDS FROM MIDDLE OF
THYROID CARTILAGE TO 4TH OR 5TH TRACHEAL RING.
• ISTHMUS EXTENDS FROM 2ND TO THE 3RD TRACHEAL
![Page 8: Thyroid anatomy and physiology](https://reader036.vdocuments.site/reader036/viewer/2022070520/58f9b127760da3da068bbdee/html5/thumbnails/8.jpg)
SURGICAL ANATOMY
![Page 9: Thyroid anatomy and physiology](https://reader036.vdocuments.site/reader036/viewer/2022070520/58f9b127760da3da068bbdee/html5/thumbnails/9.jpg)
SURGICAL ANATOMY
• EACH LOBE MEASURES 5cmX2.5cmX2.5cm• ISTHMUS MEASURES 1.2cmX1.2cm• GLAND MEASURES 25gms• LARGER IN FEMALES THAN MALES• INCREASES IN SIZE DURING PREGNANCY AND
MENSTRUATION
![Page 10: Thyroid anatomy and physiology](https://reader036.vdocuments.site/reader036/viewer/2022070520/58f9b127760da3da068bbdee/html5/thumbnails/10.jpg)
SURGICAL ANATOMY
![Page 11: Thyroid anatomy and physiology](https://reader036.vdocuments.site/reader036/viewer/2022070520/58f9b127760da3da068bbdee/html5/thumbnails/11.jpg)
SURGICAL ANATOMY
CAPSULES• TRUE PERIPHERAL CONDENSATION OF ‐
CONNECTIVE TISSUE OF GLAND
• FALSE/SURGICAL FROM PRETRACHEAL LAYER ‐OF DEEP CERVICAL FASCIA
![Page 12: Thyroid anatomy and physiology](https://reader036.vdocuments.site/reader036/viewer/2022070520/58f9b127760da3da068bbdee/html5/thumbnails/12.jpg)
SURGICAL ANATOMY
• CAPSULES
![Page 13: Thyroid anatomy and physiology](https://reader036.vdocuments.site/reader036/viewer/2022070520/58f9b127760da3da068bbdee/html5/thumbnails/13.jpg)
SURGICAL ANATOMY
SUSPENSORY LIGAMENT OF BERRY : THE PRETRACHEAL LAYER 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 GLAND TO THE CRICOID CARTILAGE
![Page 14: Thyroid anatomy and physiology](https://reader036.vdocuments.site/reader036/viewer/2022070520/58f9b127760da3da068bbdee/html5/thumbnails/14.jpg)
SURGICAL ANATOMY
WHY THYROID MOVES WITH DEGLUTITION• DURING 1ST STAGE OF DEGLUTITION• HYOID BONE MOVES UP• PULLS PRETRACHEAL FASCIA UP• THIS PULLS LIGAMENT OF BERRY UP• THIS PULLS THYROID UP
![Page 15: Thyroid anatomy and physiology](https://reader036.vdocuments.site/reader036/viewer/2022070520/58f9b127760da3da068bbdee/html5/thumbnails/15.jpg)
SURGICAL ANATOMY
• ALL STRUCTURES ENCLOSED IN THE PRETRACHEAL FASCIA MOVES UP WITH DEGLUTITION
• THYROGLOSSAL CYST-SUBHYOID BURSITIS-PRE TRACHEAL LYMPH NODES-PRE LARYNGEAL LYMPH NODES
![Page 16: Thyroid anatomy and physiology](https://reader036.vdocuments.site/reader036/viewer/2022070520/58f9b127760da3da068bbdee/html5/thumbnails/16.jpg)
SURGICAL ANATOMY
VASCULAR ANATOMY
• HIGHLY VASCULAR• TWO ARTERIES• SUPERIOR THYROID ARTERY• INFERIOR THYROID ARTERY
![Page 17: Thyroid anatomy and physiology](https://reader036.vdocuments.site/reader036/viewer/2022070520/58f9b127760da3da068bbdee/html5/thumbnails/17.jpg)
SURGICAL ANATOMY
• 3 VEINS• SUP THYROID VEIN DRAINS INTO IJV OR COMMON FACIAL V.• MIDDLE THYROID VEIN DRAINS TO IJV• INFERIOR THYROID VEIN
INTO LEFT BRACHICEPHALIC V.• A 4TH VEIN OF KOCHER’S EMERGE B/W MIDDLE
AND INFERIOR VEINAND DRAIN INTO IJV
![Page 18: Thyroid anatomy and physiology](https://reader036.vdocuments.site/reader036/viewer/2022070520/58f9b127760da3da068bbdee/html5/thumbnails/18.jpg)
SURGICAL ANATOMY
![Page 19: Thyroid anatomy and physiology](https://reader036.vdocuments.site/reader036/viewer/2022070520/58f9b127760da3da068bbdee/html5/thumbnails/19.jpg)
SURGICAL ANATOMY
LYMPHATICS• PRIMARILY TO INTERNAL JUGULAR NODES• SUPERIOR POLE & MEDIAL ISTHMUS TO
SUPERIOR GROUP• LOWER POLE OF THYROID TO INFERIOR
GROUP• EMPTY INTO PRETRACHEAL & PARATRACHEAL
NODES
![Page 20: Thyroid anatomy and physiology](https://reader036.vdocuments.site/reader036/viewer/2022070520/58f9b127760da3da068bbdee/html5/thumbnails/20.jpg)
SURGICAL ANATOMY
![Page 21: Thyroid anatomy and physiology](https://reader036.vdocuments.site/reader036/viewer/2022070520/58f9b127760da3da068bbdee/html5/thumbnails/21.jpg)
SURGICAL ANATOMY
Innervation• Principally from ANS• Parasympatheticfibers –from vagus • Sympatheticfibers –from superior, middle, and
inferior ganglia of the sympathetic trunk• Enter the gland along with the blood vessels.
![Page 22: Thyroid anatomy and physiology](https://reader036.vdocuments.site/reader036/viewer/2022070520/58f9b127760da3da068bbdee/html5/thumbnails/22.jpg)
SURGICAL ANATOMY
• RECURRENT LARYNGEAL NERVE SUPPLIES THE INTRINSIC MUSCLE OF LARYNX EXCEPT CRICOTHYROID WHICH IS SUPPLIED BY EXTERNAL LARYNGEAL NERVE
• ACIDENTAL DAMAGE TO THIS NERVE DURING SURGERY CAUSES IPSILATERAL VOCAL CORD PARALYSIS & DIFFICULTY IN PHONATION
![Page 23: Thyroid anatomy and physiology](https://reader036.vdocuments.site/reader036/viewer/2022070520/58f9b127760da3da068bbdee/html5/thumbnails/23.jpg)
SURGICAL ANATOMY
• RT SIDE IT ORIGINATES FROM VAGUS CROSSES FIRST PART OF SUBCLAVIAN.A LOOPS UNDER IT RUNS OBLIQUE TO ENTER LARYNX AT LEVEL OF CRICOID
![Page 24: Thyroid anatomy and physiology](https://reader036.vdocuments.site/reader036/viewer/2022070520/58f9b127760da3da068bbdee/html5/thumbnails/24.jpg)
SURGICAL ANATOMY
• LEFT SIDE AFTER ORIGIN FROM VAGUS CROSSES AORTIC ARCH LOOPS POSTERIORLY AROUND LIGAMENTUM ARTERIOSUS ASCENDS MEDIALLY IN TRACHEO ESOPHAGEAL GROOVE
![Page 25: Thyroid anatomy and physiology](https://reader036.vdocuments.site/reader036/viewer/2022070520/58f9b127760da3da068bbdee/html5/thumbnails/25.jpg)
SURGICAL ANATOMY
![Page 26: Thyroid anatomy and physiology](https://reader036.vdocuments.site/reader036/viewer/2022070520/58f9b127760da3da068bbdee/html5/thumbnails/26.jpg)
SURGICAL ANATOMY
• SUPERIOR LARYNGEAL NERVE HAS INTERNAL BRANCH(SENSORY) & EXTERNAL BRANCH(MOTOR)HELPS IN VOCAL CORD TENSION AND PITCH OF VOICE
![Page 27: Thyroid anatomy and physiology](https://reader036.vdocuments.site/reader036/viewer/2022070520/58f9b127760da3da068bbdee/html5/thumbnails/27.jpg)
SURGICAL ANATOMY
• SUPERIOR LARYNGEAL NERVE RUNS IN CLLOSE PROXIMITY TO SUPERIOR POLE VESSELS, TO AVOID INJURY SUPERIOR POLE VESSELS SHOULD BE INDIVIDUALLY LIGATED & DIVIDED LOW ON THYROID GLAND AND DISSECTED LATERALLY TO CRICOTHYROID MUSCLE
![Page 28: Thyroid anatomy and physiology](https://reader036.vdocuments.site/reader036/viewer/2022070520/58f9b127760da3da068bbdee/html5/thumbnails/28.jpg)
SURGICAL ANATOMY
HISTOLOGY The functioning unit is the lobule supplied by a
single arteriole and consists of 24–40 follicles lined with cuboidal epithelium. The
follicle contains colloid in which thyroglobulin is stored.
![Page 29: Thyroid anatomy and physiology](https://reader036.vdocuments.site/reader036/viewer/2022070520/58f9b127760da3da068bbdee/html5/thumbnails/29.jpg)
SURGICAL ANATOMY
HISTOLOGY • PARAFOLLICULAR CELLS(C CELLS)- LOCATED UTSIDE FOLLICLES SECRETE
CALCITONIN . – MEDULLARY CA ARISES FROM C CELLS
![Page 30: Thyroid anatomy and physiology](https://reader036.vdocuments.site/reader036/viewer/2022070520/58f9b127760da3da068bbdee/html5/thumbnails/30.jpg)
SURGICAL ANATOMY
![Page 31: Thyroid anatomy and physiology](https://reader036.vdocuments.site/reader036/viewer/2022070520/58f9b127760da3da068bbdee/html5/thumbnails/31.jpg)
EMBRYOLOGY
• The thyroglossal duct develops from the median bud of the pharynx. The foramen caecum at the base of the tongue is the vestigial remnant of the duct. This initially hollow structure migrates caudally and passes in close continuity with, and sometimes through, the developing hyoid cartilage.
![Page 32: Thyroid anatomy and physiology](https://reader036.vdocuments.site/reader036/viewer/2022070520/58f9b127760da3da068bbdee/html5/thumbnails/32.jpg)
EMBRYOLOGY
• The parathyroid glands develop from the third and fourth pharyngeal pouches
• The thymus also develops from the third pouch.• As it descends it takes the associated
parathyroid gland with it which explains why the inferior parathyroid which arises from the third pharyngeal pouch normally lies inferior to the superior gland.
![Page 33: Thyroid anatomy and physiology](https://reader036.vdocuments.site/reader036/viewer/2022070520/58f9b127760da3da068bbdee/html5/thumbnails/33.jpg)
EMBRYOLOGY
• However, the inferior parathyroid may be found anywhere along this line of descent.
• The developing thyroid lobes amalgamate• with the structures that arise in the fourth
pharyngeal pouch, i.e. the superior parathyroid gland and the ultimobranchial body.
• Parafollicular cells (C cells) from the neural crest reach the thyroid via the ultimobranchial body.
![Page 34: Thyroid anatomy and physiology](https://reader036.vdocuments.site/reader036/viewer/2022070520/58f9b127760da3da068bbdee/html5/thumbnails/34.jpg)
EMBRYOLOGY
![Page 35: Thyroid anatomy and physiology](https://reader036.vdocuments.site/reader036/viewer/2022070520/58f9b127760da3da068bbdee/html5/thumbnails/35.jpg)
Physiology The thyroid follicles secretes tri-iodothyronine(T3)and
thyroxin(T4) synthesis involves combination of iodine with tyrosine group
to form mono and di-iodotyrosine which are coupled to form T3 andT4.
The hormones are stored in follicles bound to thyrogobulin When hormones released in the blood they are bound to
plasma proteins and small amount remain free in the plasma . The metabolic effect of thyroid hormones are due to free
(unbound)T3 and T4. 90%of secreted hormones is T4 but T3is the active hormone
so, T4is converted to T3 peripherally.
![Page 36: Thyroid anatomy and physiology](https://reader036.vdocuments.site/reader036/viewer/2022070520/58f9b127760da3da068bbdee/html5/thumbnails/36.jpg)
Physiological control of secretion
Synthesis and libration of T3 and T4 is controlled by thyroid stimulating hormone(TSH)secreted by anterior pituitary gland.
TSH release is in turn controlled by thyrotropin releasing hormone (TRH)from hypothalamus .
Circulating T3and T4 exert –ve feedback mechanism on hypothalamus and anterior pituitary gland .
So, in hyperthyroidism where hormone level in blood is high ,TSH production is suppressed and vice versa.
![Page 37: Thyroid anatomy and physiology](https://reader036.vdocuments.site/reader036/viewer/2022070520/58f9b127760da3da068bbdee/html5/thumbnails/37.jpg)
PHYSIOLOGY
• IODINE –RAW MATERIAL FOR THYROID HORMONE SYNTHESIS
• INGESTED IODINE CONVERTED TO IODIDE BEFORE ABSORPTION
• 15O μg OF IODINE MINIMUM REQD FOR NORMAL THYROID FUNCTION OF WHICH 120μg ENTER THYROID AT NORMAL RATES OF HORMONE SYNTHESIS AND SECRETION
![Page 38: Thyroid anatomy and physiology](https://reader036.vdocuments.site/reader036/viewer/2022070520/58f9b127760da3da068bbdee/html5/thumbnails/38.jpg)
PHYSIOLOGY
• THYROGLOBULIN IS A GLYCOPROTEIN SYNTHESIZED IN THYROID CELLS AND SECRETED INTO THE COLLOID BY EXOCYTOSIS
• THYROGLOBULIN IS BOUND TO THYROID HORMONES TILL IT IS SECTRETED INTO BLOOD, AFTER WHICH IT IS INGESTED BACK INTO THE COLLOID
![Page 39: Thyroid anatomy and physiology](https://reader036.vdocuments.site/reader036/viewer/2022070520/58f9b127760da3da068bbdee/html5/thumbnails/39.jpg)
PHYSIOLOGY
• STEPS OF THYROID HORMONE SYNTHESIS 1. IODINE TRAPPING
2. OXIDATION3. IODINATION4. COUPLING5. STORAGE 6. RELEASE
![Page 40: Thyroid anatomy and physiology](https://reader036.vdocuments.site/reader036/viewer/2022070520/58f9b127760da3da068bbdee/html5/thumbnails/40.jpg)
PHYSIOLOGY
IODINE TRAPPING• IODINEAVAILABLE THROUGH CERTAIN FOODS (EG,
SEAFOOD, BREAD, DAIRY PRODUCTS), IODIZED SALT, OR DIETARY SUPPLEMENTS ETC
• THYROID CELL MEMBRANES FACING THE CAPILLARIES CONTAIN A SYMPORTER OR IODINE PUMP THAT TRANSPORTS Na+/I AGAINST ‐ELECTROCHEMICAL GRADIENT
![Page 41: Thyroid anatomy and physiology](https://reader036.vdocuments.site/reader036/viewer/2022070520/58f9b127760da3da068bbdee/html5/thumbnails/41.jpg)
Biosynthesis of T4 and T3
The process includes• Dietary iodine (I) ingestion• Active transport and uptake of iodide (I-) by thyroid gland• Oxidation of I- and iodination of thyroglobulin (Tg)
tyrosine residues • Coupling of iodotyrosine residues (MIT and DIT) to form
T4 and T3
• Proteolysis of Tg with release of T4 and T3 into the circulation
41
![Page 42: Thyroid anatomy and physiology](https://reader036.vdocuments.site/reader036/viewer/2022070520/58f9b127760da3da068bbdee/html5/thumbnails/42.jpg)
Regulation of TH synthesis/secretion
![Page 43: Thyroid anatomy and physiology](https://reader036.vdocuments.site/reader036/viewer/2022070520/58f9b127760da3da068bbdee/html5/thumbnails/43.jpg)
Normal circulatory concentrations
– T4 4.5-11 g/dL
– T3 60-180 ng/dL (~100-fold less than T4)
43
![Page 44: Thyroid anatomy and physiology](https://reader036.vdocuments.site/reader036/viewer/2022070520/58f9b127760da3da068bbdee/html5/thumbnails/44.jpg)
Carriers for Circulating Thyroid Hormones
• More than 99% of circulating T4 and T3 is bound to plasma carrier proteins– Thyroxine-binding globulin (TBG), binds about 75%– Transthyretin (TTR), also called thyroxine-binding
prealbumin (TBPA), binds about 10%-15%– Albumin binds about 7%– High-density lipoproteins (HDL), binds about 3%
• Carrier proteins can be affected by physiologic changes, drugs, and disease
44
![Page 45: Thyroid anatomy and physiology](https://reader036.vdocuments.site/reader036/viewer/2022070520/58f9b127760da3da068bbdee/html5/thumbnails/45.jpg)
PHYSIOLOGY
• PHYSIOLOGICAL ACTIONS• HEART INCREASE CARDIAC OUTPUT,HEART RATE• ADIPOSE TISSUE STIMULATE LIPOLYSIS
![Page 46: Thyroid anatomy and physiology](https://reader036.vdocuments.site/reader036/viewer/2022070520/58f9b127760da3da068bbdee/html5/thumbnails/46.jpg)
PHYSIOLOGY
• MUSCLE INCREASES PROTEIN BREAKDOWN• BONE PROMOTES NORMAL GROWTH AND SKELETAL DEVELOPMENT
![Page 47: Thyroid anatomy and physiology](https://reader036.vdocuments.site/reader036/viewer/2022070520/58f9b127760da3da068bbdee/html5/thumbnails/47.jpg)
PHYSIOLOGY
• NERVOUS SYSTEM PROMOTE NORMAL BRAIN DEVELOPMENT• GUT INCREASESRATE OF CHO ABSORPTION
![Page 48: Thyroid anatomy and physiology](https://reader036.vdocuments.site/reader036/viewer/2022070520/58f9b127760da3da068bbdee/html5/thumbnails/48.jpg)
Thyroid Hormone Plays a Major Role in Growth and Development
• Thyroid hormone initiates or sustains differentiation and growth– Stimulates formation of proteins– Is essential for normal brain development
• Essential for childhood growth– Untreated congenital hypothyroidism or chronic
hypothyroidism during childhood can result in incomplete development and mental retardation
48
![Page 49: Thyroid anatomy and physiology](https://reader036.vdocuments.site/reader036/viewer/2022070520/58f9b127760da3da068bbdee/html5/thumbnails/49.jpg)
Thyroid Hormones and the Central Nervous System (CNS)
• Thyroid hormones are essential for neural development and maturation and function of the CNS
• Decreased thyroid hormone concentrations may lead to alterations in cognitive function– Patients with hypothyroidism may develop
impairment of attention, slowed motor function, and poor memory
– Thyroid-replacement therapy may improve cognitive function when hypothyroidism is present
49
![Page 50: Thyroid anatomy and physiology](https://reader036.vdocuments.site/reader036/viewer/2022070520/58f9b127760da3da068bbdee/html5/thumbnails/50.jpg)
Thyroid Hormone Influences the Female Reproductive System
• Normal thyroid hormone function is important for reproductive function– Hypothyroidism may be associated with menstrual
disorders, infertility, risk of miscarriage, and other complications of pregnancy
50
![Page 51: Thyroid anatomy and physiology](https://reader036.vdocuments.site/reader036/viewer/2022070520/58f9b127760da3da068bbdee/html5/thumbnails/51.jpg)
Thyroid Hormone is Critical for Normal Bone Growth
– T3 also may participate in osteoblast differentiation and proliferation, and chondrocyte maturation leading to bone ossification
51
![Page 52: Thyroid anatomy and physiology](https://reader036.vdocuments.site/reader036/viewer/2022070520/58f9b127760da3da068bbdee/html5/thumbnails/52.jpg)
Thyroid Hormone Regulates Mitochondrial Activity
• T3 is considered the major regulator of mitochondrial activity
– A potent T3-dependent transcription factor of the
mitochondrial genome induces early stimulation of transcription and increases transcription factor (TFA) expression
– T3 stimulates oxygen consumption by the
mitochondria
52
![Page 53: Thyroid anatomy and physiology](https://reader036.vdocuments.site/reader036/viewer/2022070520/58f9b127760da3da068bbdee/html5/thumbnails/53.jpg)
Thyroid Hormones Stimulate Metabolic Activities in Most Tissues
• Thyroid hormones (specifically T3) regulate rate of
overall body metabolism– T3 increases basal metabolic rate
• Calorigenic effects– T3 increases oxygen consumption by most
peripheral tissues– Increases body heat production
53
![Page 54: Thyroid anatomy and physiology](https://reader036.vdocuments.site/reader036/viewer/2022070520/58f9b127760da3da068bbdee/html5/thumbnails/54.jpg)
Investigation
Laboratory investigation: -serum T3, T4.-serum TSH. -thyroid antibodies: in hashimoto’s disease.
![Page 55: Thyroid anatomy and physiology](https://reader036.vdocuments.site/reader036/viewer/2022070520/58f9b127760da3da068bbdee/html5/thumbnails/55.jpg)
Investigation
-chest and neck x-ray:Show descend of thyroid gland to thorax and
mediastanal shifting in retrosternal goitre. -iodine isotopesBy i.v injection of I131. Then, use gama rays to show
hot and cold nodules. -CT scanShow thyroid size and if there is compression to
trachea
![Page 56: Thyroid anatomy and physiology](https://reader036.vdocuments.site/reader036/viewer/2022070520/58f9b127760da3da068bbdee/html5/thumbnails/56.jpg)
Investigation
-Endoscopic investigation:-bronchoscopy: show compression and
infiltration of trachea by tumerBiopsy: -fine needle aspiration biopsy.-true-cut biopsy.
![Page 57: Thyroid anatomy and physiology](https://reader036.vdocuments.site/reader036/viewer/2022070520/58f9b127760da3da068bbdee/html5/thumbnails/57.jpg)
MIDLINE SWELLINGS
• Thyroid enlargement• Thyroglossal cyst• Dermoid cyst
![Page 58: Thyroid anatomy and physiology](https://reader036.vdocuments.site/reader036/viewer/2022070520/58f9b127760da3da068bbdee/html5/thumbnails/58.jpg)
THANK YOU