Question 1. Describe coverings, position, parts, relations, blood supply & applied anatomy of thyroid gland (or) Medial relations of lobe of thyroid gland (or) Name any four structures related to medial surface of thyroid gland (or) Blood supply of thyroid gland (or) Isthmus of thyroid gland
Answer:
Thyroid gland:
- Coverings
- Capsule of thyroid
1. True capsule
- It is the peripheral condensation of the connective tissue of the gland
- A dense capillary plexus is present deep to it
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2. False capsule
- It is derived from the pretracheal layer of the deep cervical fascia
Position:
- It lies against vertebrae C5, C6, C7 & T1, in front & at sides of trachea
Parts:
- Each gland consists of two lobes connected by an isthmus
Relations:
- The lobes are conical in shape having
-
- Apex
- Base
- Three surfaces
- Two borders
- Ishmus has
- Two surfaces
- Two borders
Blood supply:
- Arterial supply
Venous drainage:
Applied anatomy:
- Any enlargement of the thyroid gland is called goitre
- Hyperthyroidism causes tachycardia, tremors, exophthalmos & increased BMR
- It may require thyroidectomy, removal of gland
- For it, the superior thyroid artery is ligated near the gland & inferior thyroid artery is ligated away from the gland
- Hypothyroidism causes cretinism in infants & myxoedema in adults
- Benign tumors of the gland displaces & even compress neighboring structures
- Malignant tumors of the gland invade & erode neighboring structures
Question 2. Give an account of gross anatomy, histology, lymphatic drainage & development of thyroid gland
Answer:
Thyroid gland:
Histology:
- It is covered by a fibrous capsule
- Septa extends from capsule into gland substance & divides it into lobules
- Each lobule is made up of follicles
- Follicle has a cavity filled with colloid
- Each follicle consists of
1. Cells:
- Follicular cells
- They line the follicles
- They secrete T3 & T4 hormones
- They vary in shape according to their activity
- C cells or parafollicular cells
- They are polyhedral cells with oval nuclei
Location:
- In between follicular cells & basement membrane
2. Connective tissue stroma:
- It surrounds the follicles
- It contains capillary plexus, lymphatic capillaries & sympathetic nerves
Lymphatic Drainage:
Development:
- The thyroid gland develops from a median endodermal thyroid diverticulum This grows down in front of the neck from the floor of the primitive pharynx
- The lower end of the diverticulum enlarges to form the gland
- The rest of the diverticulum remains narrow & forms thyroglossal duct
- Most of it soon disappears
- Remnants of it forms thyroglossal cysts or fistulas
Question 3. Give origin, insertion & superficial relations of scalenus anterior muscle
Answer:
Scalenus Anterior Muscle:
- It is a paravertebral muscle
Origin:
- Anterior tubercles of transverse processes of cervical vertebrae 3, 4, 5 & 6
Insertion:
- Scalenus tubercle & adjoining ridge on the superior surface of first rib
Relations:
Question 4. Thyroid gland follicle
Answer:
- Thyroid gland is covered by a fibrous capsule
- Septa extends from capsule into gland substance & divides it into lobules
- Each lobule is made up of follicles
- Follicle has a cavity filled with colloid
- Each follicle consists of
1. Cells:
- Follicular cells
- They line the follicles
- They secrete T3 & T4 hormones
- They contains
- Golgi complex
- Lysosomes
- Microtubules
- Microfilaments
- Secretory vacuoles
- They vary in shape according to their activity
- NormallyCells are cuboidal with moderate colloid
- Inactive cellare flat with abundant colloid
- Highly active cellare columnar with scanty colloid
- They vary in shape according to their activity
- C cells or parafollicular cells
- They are polyhedral cells with oval nuclei
Location:
- In between follicular cells & basement membrane
- In connective tissue between the follicles
Contains:
- Granular endoplasmic reticulum
- Golgi complex
- Mitochondria
- Membrane bound Secretory granules
Hormone secreted:
- Thyrocalcitonin
2. Connective tissue stroma:
- It surrounds the follicles
- It contains capillary plexus, lymphatic capillaries & sympathetic nerves
Question 5. Styloid process
Answer:
- It is a long, slender and pointed bony process
- Projects downwards, forward and slightly medially from temporal bone
Situation:
- Anteromedial to mastoid process
- Descends between external and internal carotid artery and reaches side of pharynx
- Interposed between parotid gland and internal jugular vein
Relations:
Question 6. Styloid apparatus
Answer:
- Styloid process with its attached structures is called styloid apparatus
Styloid process:
- It is a long, slender and pointed bony process
- Projects downwards, forward and slightly medially from temporal bone
It contains five attachments: two ligaments and three muscles
Ligaments of styloid process:
Muscles of styloid process:
Question 7. Internal jugular vein
Answer:
Origin:
- Its origin is marked by superior bulb
- It is downward continuation of sigmoid sinus at the lower border of the jugular foramen
Termination:
- Termination is marked by inferior bulb
- It ends by joining the subclavian vein to form brachiocephalic vein behind medial end of the clavicle
Tributaries:
- Inferior petrosal sinus
- Common facial vein Lingual vein
- Pharyngeal vein
- Superior thyroid vein
- Middle thyroid vein
Relations:
Applied anatomy:
- Internal jugular vein can be cannulated by direct puncture in the interval between sternal and clavicular heads of sternocleidomastoid muscle
- In case of congestive cardiac failure, internal jugular vein is dilated and engorged
Question 8. Superior cervical ganglionsituation and branches
Answer:
- Superior cervical ganglion is largest of three ganglia
- It is spindle shaped structure
- It is 2.5 cm long
Situation:
- Below the skull
- Opposite to C2 and C3 vertebrae
- Behind carotid sheath
- Front of prevertebral fascia
Branches:
Question 9. Esophagus
Answer:
- It is a muscular food passage lying between the trachea & the vertebral column
- It is downward continuation of the pharynx
- It begins at the lower border of the cricoid cartilage, opposite the lower border of the body of vertebra C6
- It ends into cardiac end of the stomach in the abdomen
- It is about 25 cm long
Question 10. Thyroid gland
Answer:
Position:
- It lies against vertebrae C5, C6, C7 & T1, in front & at sides of trachea
Parts:
- Each gland consists of two lobes connected by an isthmus
Question 11. Accessory nerve
Answer:
- It is 11th cranial nerve
- It has two rootscranial & spinal
Functional Components:
1. Cranial root is special visceral efferent
- It arises from the lower part of nucleus ambiguus
2. Spinal root is also special visceral efferent
- It arises from a long spinal nucleus
Distribution:
1. Cranial root
- Distributed to the muscles of the palate, pharynx, larynx
2. Spinal root
- Distributed to the sternocleidomastoid & trapezius muscle
Question 12. Thyroglossal duct
Answer:
- The thyroid gland develops from a median endodermal thyroid diverticulum
- This grows down in front of the neck from the floor of the primitive pharynx
- The lower end of the diverticulum enlarges to form the gland
- The rest of the diverticulum remains narrow & forms thyroglossal duct
Most of it soon disappears - The position of the upper end is marked by the foramen caecum of the tongue
- The lower end often persists as the pyramidal lobe
Question 13. Stylohyoid ligament.
Answer:
- It extends from the tip of the styloid process to the lesser cornua of the hyoid bone
- It is derived from second branchial arch
Question 14. Recurrent laryngeal nerve (or) Recurrent laryngeal nerve of right side (or) Recurrent laryngeal nerve in the neck
Answer:
1. Right recurrent laryngeal nerve:
- It arises from the Vagus in front of the right subclavian artery It reaches through tracheooesophageal groove
- It is related to the inferior thyroid artery
- It enters the larynx behind the cricothyroid joint
2. left recurrent laryngeal nerve:
- It arises from the vagus in the thorax
- It crosses the left side of the arch of the aorta It is present posterior to the inferior thyroid artery
Structures supplied by it:
- All intrinsic muscles of the larynx except cricothyroid
- Sensory nerves to the larynx
- Cardiac branches to the deep cardiac plexus
- Branches to the trachea & oesophagus
- To the inferior constrictor
Question 15. Jugulodigastric lymph node.
Answer:
- It is the member of the anterosuperior group of the deep cervical lymph nodes
- It lies below the posterior belly of the digastric, between the angle of the mandible & the anterior border of sternocleidomastoid in the triangle bounded by the posterior belly of the digastric, the facial vein & the internal jugular vein
- It is main node draining the tonsil
Question 16. Formation & termination of internal jugular vein
Answer:
Formation:
- It is downward continuation of Sigmoid sinus at the lower border of the jugular foramen
Termination:
- It ends by joining the Subclavian vein to form the brachiocephalic vein behind medial end of the clavicle
Question 17. Scalenus anterior muscle
Answer:
Scalenus anterior muscle:
- It is a paravertebral muscle
Origin:
- Anterior tubercles of transverse processes of cervical vertebrae 3, 4, 5 & 6
Insertion:
- Scalenus tubercle & adjoining ridge on the superior surface of first rib
Actions:
- Anterolateral flexion of cervical spine
- Rotates cervical spine to opposite side
- Elevates the first rib during inspiration
- Stabilizes the neck along with other muscles
Question 18. Little’s area
Answer:
- It is common site of epitaxis
- It is an area of formation of large capillary network called the Kiesselbach’s plexus
- It is formed by anastomosis of five arteries
- Sphenopalatine artery
- Superior labial branch of facial artery
- Anterior ethmoidal artery
- Greater palatine artery
- Nasal branches of facial artery
Question 19. Muscles attached to styloid process
Answer:
Question 20. Ligaments of styloid process
Answer:
Question 21. Styloid process
Answer:
- It is a long, slender and pointed bony process
- Projects downwards, forward and slightly medially from temporal bone
- It contains five attachments: two ligaments and three muscles
Situation:
- Anteromedial to mastoid process
- Descends between external and internal carotid artery and reaches side of pharynx
- Interposed between parotid gland and internal jugular vein
Question 22. Styloid apparatus.
Answer:
- Styloid process with its attached structures is called styloid apparatus
Styloid process:
- It is a long, slender and pointed bony process
- Projects downwards, forward and slightly medially from temporal bone
It contains five attachments: two ligaments and three muscles
Ligaments of styloid process:
- Stylomandibular and stylohyoid
Muscles of styloid process:
- Styloglossus
- Stylohyoid
- Stylopharyngeus
Question 23. Ligament of Berry
Answer:
- It is suspensory ligament of pretracheal fascia
- It supports the thyroid gland and prevents it from sinking
- It provides slippery surface for free movements of the trachea during swallowing
- The thyroid gland and all thyroid swelling move upon deglutition due to attachment of thyroid to larynx
by it.
Question 24. Deep cervical lymph nodes
Answer:
Question 25. Superior cervical sympathetic ganglion
Answer:
- Superior cervical ganglion is largest of three ganglia
- It is spindle shaped structure
- It is 2.5 cm long
Situation:
- Below the skull
- Opposite to C2 and C3 vertebrae
- Behind carotid sheath
- Front of prevertebral fascia
Branches:
- Grey rami communicans
- Internal carotid nerve
- External carotid nerve
- Pharyngeal branch
- Left superior cervical cardiac nerve
- Right superior cervical cardiac nerve
Question 26. Name four muscles supplied by the recurrent laryngeal nerve.
Answer:
- Muscles supplied by the recurrent laryngeal nerve are Drains
- Intrinsic muscles of larynx posterior cricoarytenoid, lateral cricoarytenoid, transverse cricoarytenoid, oblique arytenoid, aryepiglottic, thyroarytenoid and thyroepiglottic, vocalis.
- Sensory nerves to larynx below the level of vocal cords
- Inferior constrictor of pharynx
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