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Anatomy 1 > 6) The Endocrine System > Flashcards

6) The Endocrine System Flashcards

1
Q

What is the endocrine system?

A
  • A collection of glands
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2
Q

What are the different types of glands within the body?

A
  • Exocrine glands: Have ducts that secrete hormones onto a surface (e.g. sebaceous gland)
  • Endocrine glands: Do not have ducts and secrete hormones into the blood stream (e.g. thyroid gland). They can act over relatively long distances and often there is a specific target organ
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3
Q

What is the life span of a hormone in the endocrine system?

A
  • Can last from a few hours to a few days depending on its function
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4
Q

What are the components of the endocrine system?

A
  • Pituitary (head and neck)
  • Pineal gland (head)
  • Thyroid (neck)
  • Parathyroid (neck)
  • Thymus (thoracic region)
  • Pancreas (abdominal region)
  • Suprarenals/adrenals (above the kidneys)
  • Gonads/ Ovaries in females and Testes in males (in the pelvic region)
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5
Q

Describe the development of the brain from an embryonic stage to an adult stage

A
  • The brain begins developing into three vesicle structures
  • There are three main parts of the early stage brain: Forebrain/prosencephalon, Midbrain/ mesencephalon and Hindbrain/ rhombencephalon
  • The prosencephalon is at the cephalic (head) end of the embryo followed by the mesencephalon and finally the rhombencephalon which is continuous with the spinal chord that runs to the caudal (tail) part of the embryo
  • In the 5th week of development the forebrain develops into the telencephalon (which gives rise to cerebral hemispheres) and the diencephalon (which develops into optic vesicles)
  • The hindbrain develops into the metencephalon (future pons and cerebellum) and the myelencephalon (future medulla oblangata)
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6
Q

What is the structure and function of the diencephalon?

A
  • It is located below the telencephalon and contains the thalamus, hypothalamus and part of the pituitary gland (limbic system)
  • It is responsible for motor control, relay of sensory information and control of autonomic functions
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7
Q

Where is the pituitary gland located?

A
  • The pituitary gland is an oval shaped gland located on the under surface of the brain which is attached by the infundibulum (pituitary stalk) to the hypothalamus
  • The pituitary is well protected as it is located within the pituitary fossa/sella turcica (translates to “Turkish Saddle”) part of the sphenoid bone (behind the sphenoid sinus)
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8
Q

Why is the pituitary gland called the “master endocrine gland”?

A
  • It releases hormones that act on other endocrine glands and controls the hormones they release
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9
Q

What is the cranium?

A
  • The superior aspect of the skull which encloses and protects the brain
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10
Q

What are the different bones that make up the cranium?

A
  • Frontal bone (located on the anterior portion of the skull)
  • Parietal bone (located in between the frontal and occipital bone)
  • Occipital bone (located on the posterior surface of the skull)
  • Temporal bone (located on the sides which houses the ears)
  • Sphenoid bone (located centrally)
  • ## Zygomatic/cheek bone (sits anteriorly and laterally of the sphenoid in the cheek)
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11
Q

Describe the structure of the sphenoid bone?

A
  • The sphenoid bone is butterfly shaped which consists of a body and a pair of greater and lesser wings
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12
Q

How does the pituitary secrete its hormones?

A
  • The secretion of the pituitary gland is controlled by the hypothalamus which is influenced by the information it receives from many pathways within the CNS
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13
Q

What are the secretions of the pituitary?

A
  • Prolactin: For milk production
  • Growth hormone: Stimulates growth, cell reproduction and cell regeneration
  • Thyroid stimulating hormone (TSH): Stimulates the thyroid to release thyroxine and triiodothyronine (to increase metabolism)
  • Adrenocorticotropic hormone: Increases production and release of cortisol by the cortex of the adrenal glands (to increase gluconeogenesis and metabolism)
  • Gonadotropin: Luteinizing hormone (involved in ovulation and testosterone production) and Follicle Stimulating Hormone (regulates the development, growth and reproductive processes of the body)
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14
Q

What is hypopituitarism?

A
  • The lack of production of growth hormone
  • Most commonly due to the presence of a tumour (can be benign or malignant)
  • Can lead to growth defects, problems with fertility, fatigue, problems controlling body temperature and inability to produce breast milk
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15
Q

What is the thyroid gland?

A
  • The thyroid gland is the largest endocrine gland which is highly vascularised
  • It secretes hormones that are mainly involved in metabolic activity
  • It contains two lateral lobes which are connected by a central isthmus
  • The central isthmus is retracted during a tracheotomy in order to reach the trachea and gain access to the airways (if there is something lodged)
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16
Q

Describe the structure of the thyroid gland

A
  • It is found attached anteriorly to the larynx by a layer of deep fascia which runs from C-5 to T-1
  • It contains two lateral lobes (and sometimes a third pyramidal lobe) which are connected by a central isthmus
  • The lobes have a pyramidal structure as they have an apex (at the top) and a wider base (at the bottom)
  • The isthmus overlies the tracheal rings 2-3 while the tips of the lateral lobes reach superiorly and touch the thyroid cartilage
  • The layer of fascia wraps around the thyroid gland and encloses it in with the oesophagus and trachea
  • To either side we find the carotid sheath (an extension of the fascia) where we find our jugular vein, common carotid artery and vagus nerve
  • There are also a superior and inferior parathyroid gland on the posterior surface of the thyroid gland
  • It is covered by infra-hyoid (strap) muscles anteriorly within the neck region
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17
Q

Describe the development of the thyroid gland

A
  • Early in embryological development there is a thickening in the midline of the pharynx (at the back of the tongue)
  • The thickening then becomes a diverticulum which grows inferiorly into underlying tissue which is called the thyroglossal duct
  • The duct continues to grow down and gets bilobed
  • Eventually the duct becomes solid chord of cells and the bilobed swelling becomes the thyroid glands
  • Normally the solid chord of cells with degenerate and disappear
  • However sometimes there is a small bit left over which is a remainder of the thyroglossal duct and is called the pyramidal lobe
  • This small bit of tissue extends upwards and is found just to the left of the midline
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18
Q

What is the foramen cecum?

A
  • An indentation located at the midline (posterior to the vallate papillae) and shows the point where the thyroid gland development began
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19
Q

What is a thyroglossal duct cyst?

A
  • During normal development the thyroglossal duct closes
  • However if the duct does not close (to become a solid cellular structure) it can cause secretions of mucus from the oral cavity down the duct into the neck
  • This can lead to a cyst forming which can be infected
  • This cyst is known as a thyroglossal duct cyst
  • It must be removed surgically
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20
Q

What are the secretions of the thyroid gland?

A
  • Thyroxine (increases metabolic activity)
  • Triiodothyronine (increases metabolic activity)
  • Thyrocalcitonin (lowers level of blood calcium to promote bone formation)
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21
Q

Describe the vasculature of the thyroid gland

A
  • Superior thyroid artery (Branches off from the external carotid artery)
  • Inferior thyroid artery (Branches off from the thyrocervical trunk of the subclavian artery)
  • Superior thyroid vein (Drains into internal jugular)
  • Middle thyroid vein (Drains into internal jugular)
  • Inferiro thyroid vein (Drains into the brachiocephalic vein which come together to form the vena cava)
22
Q

What are the different strap muscles that cover the thyroid gland?

A
  • Omohyoid muscle (Lateral): A muscle that runs from the scapula to the hyoid bone which depresses the hyoid bone. It has two separate bellies (portions of muscle) that are separated by an intermediate tendon.
  • Sternohyoid muscle (medial): A muscle that runs from the sternum to the hyoid bone and depresses the hyoid bone
  • Sternothyroid muscle (deep): A muscle that runs from the thyroid cartilage to the sternum and depresses the larynx
23
Q

What is the suprahyoid muscle?

A
  • Muscles that sit above the hyoid bone
24
Q

What are the different types of jugular veins?

A
  • Internal jugular veins: Running alongside the neck region leading to the brain
  • Anterior jugular veins: Forming tributaries for the thyroid gland
25
Q

What are submandibular glands?

A
  • Glands that are found just below the mandible (the lower jaw bone)
26
Q

What are the parathyroid glans?

A
  • Small ovoid shaped glands that are closely related to the posterior border of the thyroid gland
  • There are normally four of them however there is some variability
  • There are two superior parathyroid glands (that are constant in position) and two inferior parathyroid glands
  • The superior parathyroid glands sit at the middle of the posterior border of the thyroid gland
27
Q

What is the function of the parathyroid glands?

A
  • The chief cells of the parathyroid glands secrete parathyroid hormones
  • These hormones aid bone metabolism by stimulating osteoclastic activity in bones (it mobilises bone Ca2+ to increases Ca2+ levels in the blood)
  • They also stimulate the absorbtion of dietary calcium from the small intestines (via vitamin D) and in the kidneys
  • It works antagonistically to the hormones secreted by the thyroid gland (as these store Ca2+ from the blood for bone formation)
28
Q

How is the release of parathyroid hormones controlled?

A
  • It is regulated by the calcium levels in the blood via a negative feedback loop.
  • If there are high calcium levels there will be an inhibition of secretion of parathyroid hormones from the parathyroid glands it will cause calcium to be absorbed
  • If there are low calcium levels there will be an increased secretion of parathyroid hormones from the parathyroid glands it will cause calcium to be mobilised
29
Q

What is hyperparathyroidism?

A
  • This is when too much parathyroid hormones are released

- There are very few symptoms and is usually diagnosed during regular blood tests

30
Q

What is hyperparathyroidism?

A
  • This is when too much parathyroid hormones are released

- There are very few symptoms and is usually diagnosed during regular blood tests

31
Q

What is hypoparathyroidism?

A
  • This is when too little parathyroid hormones are released
  • It is very rare with more symptoms (than hyperparathyroidism)
  • It is treated with oral calcium and vitamin D analogues
32
Q

What is the pancreas?

A
  • It is a long lobulated organ which sits just left of the midline and passes to the left
  • It is retroperitoneal and so is plastered to the posterior abdominal wall (except for the tail)
  • ## It is an exocrine (due to the secretion of enzymes) and an endocrine (due to the secretion of hormones) organ
33
Q

Why do we use the subcoastal plane rather than the transpyloric plane when describing the location of the pancreas?

A
  • The transpyloric plane is a plane that intersects the pylorus of the stomach
  • Since the stomach is not fixed in place this plane is very mobile and can change place/level
  • The subcoastal plane is the plane found below the coastal margin and (since the ribs are immobile) it cannot move/change place
34
Q

What is the uncinate process?

A
  • The part of the pancreas that passes around (underneath) the mesenteric vessels
  • Hence this part of the pancreas can get affected if there is a disorder of the mesenteric vessels
35
Q

Describe the structure and location of the pancreas

A
  • It consists of a head which is nestled in the duodenum (C-shaped part of the small intestine), the neck extends across the front of the abdominal aorta (underneath the coeliac trunk), a body and a tail (which is mobile
  • It is found on the posterior abdominal wall (posterior to the stomach) in the epigastric region and extends to the upper left quadrant (called the left hypochondrium)
  • It sits at the level of the transpyloric plane (plane that intersects the pylorus of the stomach on L1) or the subcoastal plane (located just below the coastal margin)
36
Q

How does the pancreas function as an exocrine organ?

A
  • It produces secretion consisting of enzymes that run along the main pancreatic duct and join with the bile duct where they then empty into the second part of the duodenum
  • The two ducts perforate the duodenum at the major duodenal papilla
  • There is sometimes an extra pancreatic duct (called duct of Santorini) which opens a little more superior into the minor duodenal papilla
37
Q

How does the pancreas function as an endocrine organ?

A
  • It secretes hormones to help maintain sugar and salt balance
  • A small percentage of the pancreas is made of endocrine cells which are clustered into groups called the pancreatic islets or the islets of Langerhans
38
Q

Describe the structure of the suprarenal/adrenal glands

A
  • They sit on the superior pole of each kidney (however they are separate from the kidney as they have their own fascial sheet
  • They are retroperitoneal and so are plastered to the abdominal wall
  • The right gland is pyramidal while the left one is crescentic in shape
  • Each adrenal gland consists of an outer cortex and inner medulla
39
Q

What are the ovaries?

A
  • They produce oestrogen and progesterone
  • They lie underneath a peritoneal sheet (called the broad ligament)
  • They are suspended within a sheet of peritoneum.
  • They are attached to the lateral walls of the uterus by a ligamentous structure (called the ovarian ligament)
  • They sit posterior to the bladder and anterior to the rectum
40
Q

What are the testes?

A
  • They produce testosterone
  • They are suspended in the scrotum by the spermatic chord
  • The spermatic chord consists of ductus (vas) deferens, testicular arteries, testicular veins, lymphatics and other structures
  • The testicular artery and vein attach high in the posterior abdominal wall (L2)
41
Q

What can cause blood pooling in the left testicle?

A
  • If there is compression of the left renal vein then the left testicular vein cannot drain adequately and so there will be a pool of blood around the left testicle
42
Q

Describe the vasculature of the testes

A
  • The right testicular vein drains blood directly into the inferior vena cava and the left testicular vein drains blood into the left renal vein
  • This is because the inferior vena cava sits just to the right of the midline
  • The walls of the scrotum contains dartos muscle which can contract to change the surface area and is involved in helping with temperature control of the testes.
  • There is a plexus of veins (a network of veins arranged in meshes) located around the spermatic chord (called the pampiniform plexus) which helps cool incoming arterial blood
  • This maintains a low temperature for the testes so that the spermatozoa are at optimum temperature
  • These plexus come together to form the single testicular vein that drains back into circulation
43
Q

What is the thymus?

A
  • The thymus gland is a lobulated lymphoid organ which is located at the bottom of the neck and in the thoracic cavity
  • It is involved in the development of the immune system in adolescents
  • It enlarges during childhood and after puberty it atrophies (decreases in size) slowly and becomes replaced by fat
  • It secretes thymosin which stimulates the maturation and production of T-lymphocytes
  • It consists of two lobes situated behind the sternum and upper part of the chest
  • In some individuals it can extend upwards and touch the lower border of the thyroid gland
44
Q

What is the pineal gland?

A
  • It is a small pine-shaped endocrine gland that is located close to the midbrain (within the brain)
  • It is found between the two hemispheres and is attached via a stalk
  • It mainly secretes melatonin which is invovled with the circadian rhythm of the body (i.e. it maintains the bilogical clock)
  • It also secretes hormones that affect and can inhibit other glands within the endorine system
  • It is larger in childhood but shrinks at puberty and can even be calcified in middle age and so can be identified on a radiograph and CT scans of the head
  • It plays a role in breeding, hibernation and sexual developement in other animals
45
Q

What causes precocious puberty?

A
  • Pineal tumours have been linked to precocious puberty as a pineal tumour in children can cause accelerated puberty
46
Q

What are the triangles of the neck?

A
  • The neck is divided into triangles
  • There is an anteriror and a posterior triangle that is divided by the sternocleidomastoid muscle
  • It attaches to the sternum (Sterno) along with the clavicle (cleido) and rises where it attaches to the mastoid process (part of the temporal bone underneath the ear which is palpable)
47
Q

What are the boundaries of the posterior triangle of the neck?

A
  • Anterior border: Posterior border of the sternocleidomastoid muscle
  • Posterior border: Anterior border of the trapezius muscle (big broad muscle on the back of the neck and down into the upper part of the chest wall)
  • Inferior border: Superior border of the clavicle
48
Q

What are the boundaries of the posterior triangle of the neck?

A
  • Anterior border: Midline
  • Posterior border: Anterior border of the sternocleidomastoid muscle
  • Superior border: Inferior border of the mandible (lower jaw bone)
49
Q

Why is the hyoid bone unique?

A
  • It does not have any articulation with any other bones (only muscles)
50
Q

What does the anterior triangle consist of?

A
  • Strap muscles
  • Hyoid bone
  • Submandibular salivary gland
  • Larynx and trachea
  • Carotid artery
  • Internal jugular vein
51
Q

What does the posterior triangle consist of?

A
  • Accessory nerves (cranial nerve that supplies the sternocleidomastoid muscle and the trapezius muscle)
  • Scalene muscles (sitting within the posterior triangle consisting of an anterior, middle and posterior scalene muscle)
  • The beginning of the brachial plexus (plexus of nerves that supply the upper limb

Anatomy 1 (8 decks)

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