Download Endocrine Module: Anatomy Room: Master

Endocrine Module: Preparation for the Anatomy Room
The learning methods for anatomy in the Endocrine Module will be exactly the same
as those for the Respiratory Module. There will be 3 strands, anatomy in the Cuschieri
Surgical Skills Centre, supported by self-access PowerPoint presentations on
radiology and on histology. Do use all three as they are designed to complement each
other. Starting on Monday Oct 13th, come to the Skills Centre in your groups as
indicated by the timetable.
It would be helpful to read through the whole of this schedule before you come.
Station 1
Dorsum of foot and ankle for dorsalis pedis pulse
The anterior tibial artery is a branch of the popliteal artery that is the continuation of the
femoral. As the name implies the anterior tibial lies within (and supplies) the muscles in the
leg, anterior to the tibia. The artery becomes superficial at the ankle, and on the dorsum of
the foot it is palpable as the dorsalis pedis arterial pulse between the tendons of extensor
digitorum longus and extensor hallucis longus.
Look at the prosection of the dorsum (back) of the foot and ankle. Pin 1 is the tendon of
extensor digitorum longus going to the 2nd toe; pin 2 is the tendon of extensor hallucis
longus; pin 3 is the dorsalis pedis artery (with the deep fibular nerve emerging alongside it).
In your small groups, slip off a shoe and turn down your sock to show the ankle and dorsum
of the foot. Pull the toes upward, i.e. dorsiflexion or extension. Observe and palpate the
extensor tendons. When you have identified their positions, relax and palpate the dorsalis
pedis pulse between the tendons of extensors hallucis and digitorum longus.
Q. Why is palpating the dorsalis pedis pulse important in the Endocrine Module?
Station 2
Suprarenal (adrenal) gland on posterior abdominal wall
Study the prosection, which is of the central and left, upper, posterior abdominal wall.
Identify the aorta (1), the inferior vena cava (IVC) (2), the left renal vein (3) and the left
kidney (4).
Q. What are the two aortic branches, 5 and 6?
Identify the left suprarenal or adrenal gland (7), lying on the diaphragm (9) at the upper pole
of the left kidney. Note the large vein (8) draining the suprarenal to the left renal vein.
Q. Are these structures intraperitoneal or retroperitoneal?
Q. To where does the right suprarenal or adrenal vein drain?
Q. In this prosection, which 3 structures that lie anterior to and adjacent to the left suprarenal
gland have been removed?
Q. The suprarenal is divided into a cortex and a medulla. Which hormones are secreted by
the medulla? Name 1 hormone secreted by the cortex.
Station 3
Neck to show thyroid gland and its relations
Identify the thyroid gland (4,4,5) clasping the trachea (1) and lower larynx (2). The common
carotid arteries (3) lie on either side. The strap muscles in the front of the neck (sternohyoid
and sternothyroid) have been removed, as has the pre-tracheal fascia that normally surrounds
the thyroid gland. Identify the thyroid lobes (4) and the isthmus (5). Occasionally the
isthmus has a small pyramidal lobe extending upward from it.
Embryologically, the thyroid gland develops from the base of the tongue and migrates
inferiorly down the neck, to the position seen here. The residual thyroglossal duct usually
obliterates but regions of the duct may remain patent and give rise to thyroglossal cysts.
Palpate your own larynx and feel how it elevates on swallowing.
The thyroid is highly vascular and supplied by the superior thyroid branch of the external
carotid artery, and the inferior thyroid branch of the subclavian via the thyrocervical trunk.
Q. Which thyroid hormones maintain basal metabolic rate?
Q. Does the thyroid gland move up and down with the larynx on swallowing?
Q. Which vein and nerve lie within the carotid sheath with the common carotid artery?
Q. If a patient presented to you with a small, cystic, midline swelling in the anterior neck,
why would you ask him/her to put out his/her tongue and to swallow while you palpated
and observed the swelling?
Q. When removing the thyroid gland or parts of it the surgeon must locate and ligate (tieoff) the thyroid arteries. What structures may be injured?
Station 4
Separated thyroid gland, posterior surface showing, to discuss the parathyroid glands
This is the posterior aspect of the right lobe of the thyroid gland, with left and right
lobes connected by the isthmus.
There are usually 4 parathyroid glands, but the number and their positions are variable.
They lie within the thyroid capsule, applied to the posterior aspect of the left and the right
lobes, 1 near each upper pole and 1 near each lower pole. They secrete parathormone that
mobilises calcium from the bone to raise serum calcium. Consequently, the parathyroids
are necessary for life. They also promote the mobilisation of phosphorous from bone and
increase its urinary excretion.
There is considerable anastomosis between the left and right arteries and between the
superior and inferior arteries that supply the thyroid gland. An anastomotic channel
between the latter two passes close to the parathyroids and is a landmark for their surgical
location.
Q. Parathormone raises serum calcium. Which hormone released by the thyroid gland
lowers serum calcium?
Q. Why may hypocalcaemia (low serum calcium) be an important complication following
removal of the thyroid?
Q. High serum calcium will lead to high levels of excreted calcium in the urine, possibly
leading to urinary stones or calculi. Would these be a complication of hyper or hypo
parathyroidism?
Station 5
Pancreas on posterior abdominal wall
The exocrine function of the pancreas will be discussed in the Gastro-intestinal Module.
But for now identify the pancreas (1), which lies retroperitoneally across the upper,
posterior abdominal wall. Find the head, neck, body, and tail. There should be an uncinate
process extending from the head, but it is not visible here. Note how the pancreas lies
within the C-shaped curve of the duodenum (2).
Visible only by microscopy, the islets of Langerhans are scattered throughout the pancreas
to secrete insulin (B cells) and glucagon (A cells), which control blood sugar.
Q. What is the function of insulin and (briefly) how does it work?
Q. What stimulates the secretion of insulin?
Q. What is the function of glucagon and (briefly) how does it work?
Q. What stimulates the secretion of glucagon?
Q. Briefly, what is diabetes mellitus and do you know any relatively common
complications of the disease?
Station 6
Female pelvis for ovary, and plastic model of female pelvis
First of all identify the ovary (1). Then quickly review the other organs of the female
reproductive system: vagina (2); uterus (3); uterine (Fallopian) tube (4). Note their close
proximity to the bladder (5) anteriorly and the rectum (6) posteriorly. This pelvic region
will be revisited in the Reproductive Module next year.
Under the cyclical control of the pituitary gland, the ovary secretes oestrogen that not only
ensures the female secondary sex characteristics, but also stimulates the proliferative phase
of uterine epithelium during the early stage of the menstrual cycle while the follicle is
forming in the ovary. At ovulation, the follicle secretes the ovum and then becomes the
corpus luteum, which secretes progesterone that stimulates the secretary phase of the
uterus, preparing it for implantation of a developing embryo and placenta. But if there is no
pregnancy, the corpus luteum diminishes, progesterone secretion falls off and menstruation
occurs.
Q. Which pituitary hormone promotes the formation of the ovarian follicle and the
secretion of oestrogen in the first half of the menstrual cycle?
Q. A spike of which pituitary hormone stimulates ovulation and then the formation of the
corpus luteum?
Q. After the menopause, when the ovary has no more follicles and cannot secrete oestrogen
and progesterone, there is a relatively common affect on the skeletal system. What is it?
Look at the ovary in the specimen again. Find the ureter (7) behind it and the obturator
nerve (8) lateral to it.
Q. Why is it important to remember the close proximity of these structures to the ovary?
Station 7
Testis and plastic model of male pelvis
The testis will be reviewed again in the Reproductive Module. Ordinarily it is suspended on
its vascular pedicle within the scrotum. As well as the function of spermatogenesis, the
testis also secretes testosterone which promotes the male secondary sex characteristics and
protein anabolism (the body-builder’s dream). Testosterone is formed by the Leydig cells in
the interstitial tissue between the seminiferous tubules.
Q. In the male, which pituitary hormone is the equivalent of female luteinizing hormone
and promotes testosterone formation?
Q. As the testis is suspended on its vascular pedicle, do you think it could twist around in
the scrotum and obstruct its blood supply?
Q. From where do the testicular vessels and nerves arise?
Station 8
Sagittal section of the head to show the pituitary gland and the hypothalamus.
Look at the hypothalamus (1) connected to the pituitary gland (2) by the pituitary stalk (3).
The hypothalamus is part of the brain and this is the neuro-endocrine link (hypothalamus to
pituitary gland) that largely controls the rest of the endocrine system.
The optic nerves (sight) come together in the optic chiasma (4) just above and in front of
the pituitary gland. The gland itself sits in the pituitary fossa of the sphenoid bone,
immediately above the sphenoidal air sinus (5), behind the nasal cavity.
The pituitary gland, also known as the hypophysis, has a posterior neurohypophysis and an
anterior adenohypophysis.
The neurohypophysis is directly connected to the hypothalamus by nerves and secretes
antidiuretic hormone (ADH) to control water reabsorption in the kidney and oxytocin to control
muscle contraction in the uterus and mammary gland.
The adenohypophysis secretes many trophic hormones i.e. hormones that stimulate or regulate
the other glands within the endocrine system. A portal circulation carrying releasing factors from
the hypothalamus to the adenohypophysis controls its hormone release. Feedback mechanisms
also occur so that low levels of circulating hormone may stimulate the production of releasing
factors in the pituitary and vice versa, high circulatory levels feedback to decrease further
release.
Body growth, growth hormone (GH, somatostatin)
Adrenal cortical function, adrenocorticotrophic hormone (ACTH)
Thyroid function, thyroid stimulating hormone (TSH)
Cyclical ovarian function, (FSH, LH)
Spermatogenesis (ICSH), ICSH is often seen as the male analogue of either FSH, LH or
prolactin in the female.
Pigmentation, melanocyte stimulating hormone (MSH)
Milk secretion from the developed breast, prolactin
Q. Based on the above list of functions, how do you think a patient with a pituitary tumour may
present to your clinic?
Q. Do you think a patient with a pituitary tumour could present with “eye signs”, and would it be
necessary to assess the visual function of a patient in whom you suspected a pituitary tumour?
Q. Looking at the anatomy of these two specimens, how do you think a pituitary tumour may be
removed?