Anatomy of Thyroid & Parathyroid Glands Flashcards
(117 cards)
1
Q
What is the proliferation process of all glands?
A
All glands begin with the proliferation of epithelial cells and their downward growth into the underlying connective tissue
2
Q
What is the role of the basal laminate in regards to the proliferating cells of the glands?
A
The basal laminate provides a supporting structure for the proliferating cells
3
Q
What is the pathway of the exocrine glands?
A
- The proliferated cells remain connected to the epithelial surface.
- A duct forms, through which secretions are transported to the epithelial surface.
- The secretory portion (acinus) develops at the end of the duct.
4
Q
What is the pathway of the endocrine glands?
A
- The connection to the epithelial surface disappears.
- The cells arrange themselves into either:
–> Cords of cells
–> Follicles
5
Q
What are cords of cells in the endocrine gland?
A
Associated with capillaries to release hormones directly into the bloodstream.
6
Q
What are follicles in the endocrine glands?
A
Hollow spherical structures that store secretory products temporarily before releasing them into the surrounding capillaries
7
Q
What are different examples of endocrine glands? What do they secrete? (8)
A
- Pituitary –> Growth hormone & Thyroid stimulating hormone (TSH)
- Thyroid
- Pancreas –> Insulin
- Placenta –> Progesterone and Estrogen
- Testis –> Testosterone, estradiol, androstenedione
- Ovary –> Progesterone, testosterone, estradiol, androstenedione
- Adrenal Glands –> Cortex –> Cortisol, aldosterone, dehydroepiandrosterone, androstenedione
–> Medulla –> Epinephrine, norepinephrine - Pineal –> Melatonin
8
Q
What are the layers of the deep cervical fascia?
A
- Investing Layer
- Pretracheal Fascia
- Prevertebral Fascia
9
Q
What do the layers of the deep cervical fascia form?
A
The carotid sheath
10
Q
What is the investing layer?
A
The outermost layer of the deep cervical fascia surrounds the entire neck, surrounding superficial muscles like the sternocleidomastoid (SCM) and trapezius
11
Q
Which glands does the investing layer enclose?
A
Encloses the submandibular gland and forms the capsule of the parotid gland
12
Q
What are the superior attachments of the investing layer of the deep cervical fascia?
A
Superiorly –> External occipital protuberance and the superior nucha line of the skull
13
Q
What are the inferior attachments of the investing layer of the deep cervical fascia?
A
Spine and acromion of the scapula, the clavicle, and the manubrium of the sternum
14
Q
What are the posterior attachments of the investing layer of the deep cervical fascia?
A
Nuchal ligament of the vertebral column
15
Q
What are the anterior attachments of the investing layer of the deep cervical fascia?
A
Hyoid bone
16
Q
What is Ludwig’s angina?
A
Acute infection of the submandibular fascial space and is commonly seen secondary to dental infection
17
Q
What are the different parts of the pretracheal fascia?
A
Muscular part and Visceral part
18
Q
What is the muscular part like?
A
It is a round muscle which encloses the infrahyoid muscles
19
Q
What are the infrahyoid muscles?
A
3 to 4 muscles below the hyoid
20
Q
What is the visceral part of the pretracheal fascia like?
A
It encloses the thyroid gland, trachea, and esophagus
21
Q
How many layers does the pericardium have?
A
3
22
Q
Why does the thyroid gland move up and down when swallowing? Is it normal?
A
It is normal for the thyroid to move up and down when swallowing, it is because of its attachment to the pre-tracheal fascia
23
Q
What is the superior attachment of the prevertebral layer?
A
Base of the skull
24
Q
What is the inferior attachment of the prevertebral layer?
A
Endothoracic fascia of the rib cage
25
What is the posterior attachment of the prevertebral layer?
Nuchal ligament of the vertbral column
26
What is the anterior attachment of the prevertebral layer?
Transverse processes and vertebral bodies of the vertebral column
27
What is the retropharyngeal space?
The space between the prevertebral fascia and the buccopharyngeal fascia, it includes lymphnodes
28
What happens if the lymph nodes of the retropharyngeal space get enlarged?
They can get enlarged due to infection or malignancy --> which will cause dysphagia
29
Which carotid artery is within the carotid sheath?
Internal carotid artery
30
What are the contents of the carotid sheath?
1. Common carotid artery (and internal carotid artery above the bifurcation).
2. Internal jugular vein.
3. Vagus nerve (CN X).
4. Deep cervical lymph nodes.
31
Where does the external carotid artery branch off to?
Head and neck
32
What is the location of the thyroid gland?
Root of the neck, anterior to the larynx, ventral to C5 to T1
33
What is the function of the thyroid gland?
It is an endocrine gland which secretes:
1. Thyroxine (T4)
2. Triiodothyronine (T3)
3. Calcitonin
34
What is the function of T3 and T4?
Metabolic functions of the body
35
What is the function of Calcitonin?
Calcium metabolism
36
What is the structure of the thyroid gland?
It is a butterfly-shaped (cone-shaped) organ that has two lobes and the isthmus which connects the lobes
37
Where is the apex of the thyroid gland?
At the oblique line of the thyroid cartilage
38
Where is the base of the thyroid gland?
At the 5th or 6th tracheal ring
39
What are the anterolateral relations to the thyroid gland?
Superior belly of omohyoid
Anterior border of sternoclidomastoid
Sternohyoid and sternothyroid muscles
40
What are the medial relations to the thyroid gland?
Thyroid and cricoid cartilages
Upper 6 tracheal rings
41
What are the posterior relations to the thyroid gland?
Carotid sheath & acquainted structures
Inferior thyroid artery
Parathyroid glands
Recurrent laryngeal nerve
42
What is the recurrent laryngeal nerve a branch of?
The vagus nerve
43
Where are the left and right recurrent laryngeal nerves derived from?
Left --> arch of aorta
Right --> subclavian artery
44
In patients with goiter, how does the relation between thyroid and trachea affect patients?
The close relationship between the thyroid lobes and the trachea commonly results in pressure on the trachea
45
What is a retrosternal goiter, when does it happen and what can it lead to?
Retrosternal goiter occurs when the thyroid is abnormally located behind the sternum; it can compress the trachea and cause dangerous dyspnea and severe venous compression
45
Where is the isthmus of the thyroid located?
Passes anterior to the 2nd to 4th tracheal rings, encompasses a cranially extending thyroid tissue usually left to midline
46
What is the Pyramidal lobe?
It is only found in 50% of individuals; the distal end of the thyroglossal gland
47
In case that the pyramidal lobe is present, what structure connects it to the hyoid bone?
A fibromuscular band connects the pyramidal lobe to the hyoid bone; the muscular part is the levator glandulae thyroideae
48
What is the levator glandulae thyroideae?
Embryological remnants of the thyroglossal duct, which in most cases completely disappears
It elevates the thyroid gland
49
What are the anterior relations of the isthmus? (4)
1. Sternothyroids
2. Sternohyoids
3. Anterior jugular veins
4. Fascia and skin
50
What are the posterior relations of the isthmus? (3)
1. 2nd ring of trachea
2. 3rd ring of trachea
3. 4th ring of trachea
51
What is the importance of knowing the location of the anterior jugular vein?
In cases where the trachea has to be reached through tracheostomy, the location of ther vein needs to anterior jugulabe known so that it is not hurt
51
What is the fascial covering of the thyroid gland?
Thin fibrous capsule --> Capsula glandulae thyroidea
52
What are the relations of the fascial covering of the thyroid gland?
Anterior --> Pretracheal layer
Posterolateral --> Carotid sheath
52
What does the fascial covering attach the gland to posteriorly?
Cricoid cartilage and upper tracheal rings
53
What are the arteries of the thyroid gland?
1. External carotid artery --> which gives rise to superior thyroid artery
2. Throcervical trunk --> which gives rise to inferior thyroid artery
3. Arch of the aorta or Brachiocephalic --> which give rise to thyroidea ima
54
In what % of the population is the thyroidea ima artery present?
10%
55
Which nerve is related to the superior thyroid artery?
External laryngeal nerve
56
Which nerve is related to the inferior thyroid artery?
Recurent laryngeal nerve
57
Which nerve runs with the thyroidea ima artery?
No nerve runs along with it, but clinical relevance to tracheostomy along with anterior jugular vein
58
What are the veins of the thyroid?
1. Superior thyroid vein
2. Middle thyroid vein
3. Inferior thyroid vein
59
Where do the superior and middle thyroid veins drain into?
Internal jugular vein
60
Where does the inferior thyroid vein drain into?
Left brachiocephalic vein
61
What is the lymph drainage of the thyroid gland (superiorly)?
Prelaryngeal lymph nodes
62
What is the lymph drainage of the thyroid gland (inferiorly)?
Pretracheal lymph nodes
63
What is the lymph drainage of the thyroid gland (medially)?
Paratracheal lymph nodes
64
What is the lymph drainage of the thyroid gland (laterally)?
Inferior deep cervical lymph nodes
65
Where do all the thyroid lymph nodes drain into?
Deep cervical lymph nodes
66
What are the innervations of the thyroid gland?
Sympathetic and Parasympathetic
67
What are the nerves of the sympathetic nervous system that are associated with the thyroid gland?
Superior cervical ganglia
Middle cervical ganglia
Inferior cervical ganglia
68
How do the sympathetic ganglia reach the thyroid?
Through superior and inferior thyroid periarterial plexuses
69
What are the nerves associated with the parasympathetic nervous system of the thyroid gland?
Vagus nerve (X)
--> Superior laryngeal nerve
--> Recurrent laryngeal nerve
70
What is the autonomic innevration of the thyroid gland like?
Mainly vasomotor, endocrine secretion is hormonally regulated by the pituitary gland
71
What are the microscopic features of the thyroid gland?
Follicles
Follicular cells
Parafollicular cells
72
What are follicles?
Spherical cyst-like structures
73
What do the follicles of the thyroid gland contain?
Colloid material (T3 and T4 bound to thyroglobulin)
74
What do follicles become?
Follicular (principal) cells
75
What are follicular cells?
Single layer of epithelial cells which secrete T3 and T4
76
What is the secretion of T3 and T4 like?
Extracellular, and can be stored for a long time, in case there is no stimulus for the hormones to be released, they can be stored up to 3 months
77
What is the epithelium of follicular cells like?
When hyperactive: columnar
When at rest: squamous
78
What are parafollicular (C) cells?
They are larger and less stained than follicular cells and they secrete calcitonin
79
Where are parafollicular cells found?
In the middle of the thyroid gland
80
What is the embryonic structure of Parafollicular cells?
Pharyngeal endoderm, 4th or 5th pharyngeal pouch
81
What is the development of the thyroid gland like?
From median endodermal thickening in the floor of the pharynx, between the first and second pharyngeal arches
82
What does the descent of the thyroid gland begin with?
With the growth of the embryo and root of the tongue
83
What is the descent of the thyroid gland like?
Descends and enlarges ventral to the hyoid bone
84
What is the thyroid like in the early stages of development?
It is hollow in the early stages of development
85
What does the thyroid become like later on in its development process?
Becomes a solid mass that divides into two lobes connected by an isthmus
86
What connects the thyroid to the tongue?
The thyroglossal duct
87
When does the thyroglossal duct attain its final shape and destination?
Week 7
88
What happens to the thyroglossal duct?
It degenerates and disappears
89
What does the proximal opening of the thyroglossal duct persist as?
Foramen cecum
90
What does the distal end of the thyroglossal duct persist as?
Pyramidal lobe
91
What is a thyroglossal cyst?
A remnant of thyroglossal duct that persists and forms a cyst in the anterior part of the neck
92
What happens if there is an internal opening of the thyroglossal cyst?
Thyroglossal fistula
93
What are the presentations of thyroglossal cyst?
Painless, enlarged movable median mass
Asymptomatic unless it becomes infected
94
Where are thyroglossal cysts usually located?
In the midline of the neck, close to the hyoid bone
95
What is a thyroglossal sinus?
After infection of the thyroglossal cyst, perforation of the skin occurs in the neck anteriorly, opens cyst to the outside
96
What are the ectopic thyroid tissues?
In the tongue: lingual thyroid tissue
In the anterior neck: along the root of the thyroglossal duct, usually at or inferior to the hyoid bone --> sublingual thyroid tissue
97
What causes ectopic thyroid tissue?
Frequently due to incomplete descent of the thyroid gland, only thyroid tissue is present
98
Which is the most common ectopic thyroid tissue location?
Lingual thyroid tissue
99
What is the parathyroid gland?
Small, flattened, and oval in shape, it lies outside fibrous capsule of posterior surface thyroid goland
100
How many glands does the parathyroid gland usually have?
Usually 4, two superior and two inferior
101
Where are the superior glands of the parathyroid found?
Level of the inferior border of the cricoid cartilage: just because the name is "superior," it does not mean they are found on the superior part of the thyroid
102
Where are the inferior glands of the parathyroid found?
Level of inferior poles of thyroid gland
103
What % of individuals have more than four glands of the parathyroid?
5%
104
What is the arterial supply of the parathyroid gland?
Superior and inferior thyroid arteries
However, in some cases, both superior and inferior glands are supplied by inferior thyroid arteries only
105
What is the venous drainage of the parathyroid gland?
Parathyroid veins into thyroid plexus of veins
106
How are the endocrine cells of the parathyroid arranged?
In cords
107
What are the two types of cells of the parathyroid gland?
Chief cells and oxyphil cells
108
WHat are chief cells like?
Small polygonal cells, slightly acidophilic cytoplasm
Granules in their cytoplasm --> parathyroid hormone
109
What is the main regulator of parathyroid hormone?
Calcium levels of the body
110
What is the function of parathyroid hormone and where does it function?
Increases calcium, and functions in the DCT and collecting duct of the kidneys, bones
111
What are the oxyphil cells like?
Smaller in population but larger polygonal cells, the cytoplasm contains many acidophilic mitochondria
Transitional derivatives of chief cells
112
What is the development of the superior parathyroid glands like?
Develop from endodermal cells of the fourth pharyngeal pouch
113
What is the development of the inferior parathyroid glands like?
Arise together with the thymus gland from endodermal cells of the third pharyngeal pouch
114
