The Ear

• The ear contains the vestibulocochlear organ and consists of three main parts: external, middle, and internal.
• It has two functions, balance and hearing.

• The tympanic membrane (eardrum) separates the external ear from the middle ear.
• The auditory tube joins the middle ear or tympanic cavity to the nasopharynx.

The Arteries of the Face

• The superficial arteries are derived from the external carotid arteries.

The Facial Artery

• This is the chief artery of the face.
• It arises from the external carotid artery and winds its way to the inferior border of the mandible, just anterior to the masseter muscle.
• It hooks around the inferior border of the mandible and grooves the bone. Here the artery is superficial, just beneath the platysma and its pulsation can be felt.

• In its course over the face to the medial angle of the eye, the facial artery crosses the mandible, buccinator muscle, and maxilla.
• It lies deep to the zygomaticus major.

• The facial artery ends by sending branches to the lip and side of the nose.
• The part of the artery that runs along the side of the nose to supply the eyelids is called the angular artery.

The Superficial Temporal Artery

• This artery is the smaller of the two terminal branches of the external carotid artery (the other is the maxillary artery).
• It begins deep to the parotid gland, posterior to the neck of the mandible, and ascends superficial to the posterior end of the zygomatic process of the temporal bone. It then enters the temporal fossa.

• The superficial temporal artery ends in the scalp by dividing into the frontal and parietal branches.

• Pulsation of this artery can be felt by compressing the root of the zygomatic process of the temporal bone.

The Transverse Facial Artery

• This small artery arises from the superficial temporal artery before it emerges from the parotid gland.
• It crosses the face superficial to the masseter muscle, about a fingerbreadth inferior to the zygomatic arch.
• It divides into numerous branches that supply the parotid gland and duct, the masseter muscle, and the skin of the face.

• It anastomoses with branches of the facial artery.

3 basic functions
o    protection of respiratory tract during swallowing food/air pathways cross.
    epiglottis provides protection
o    control intra-thoracic pressure (in coughing) -    close off airway to build pressure then rapidly open to release stuff
o    production of sound (in speaking, singing, laughing)

Important structures

o    hyoid bone
o    thyroid cartilage
o    arytenoids cartilage: vocal and muscle process
    sits on slope on posterior side of cricoid - spin and slide
o    cricoid cartilage: signet ring
o    thyroepiglottic ligament

Membranes and ligaments

o    membrane: general; ligament: thickening of membrane
o    folds: free edges of membranes or ligaments
o    names: tell you where located

Important membranes:
    quandrangular/vestibular membrane—from epiglottis to arytenoids
•    inferior edge: false vocal fold
    thyrohyoid membrane
    conus elasticus = cricothyroid = cricovocal
•    superior/medial edge = vocal fold
•    vocal ligaments: true folds, top of cricothyroid membrane

The Orbital Margin

• The frontal, maxillary and zygomatic bones contribute equally to the formation of the orbital margin.

• The supraorbital margin is composed entirely of the frontal bone.
• At the junction of its medial and middle thirds is the supraorbital foramen (sometimes a notch), which transmits the supraorbital nerves and vessels.

• The lateral orbital margin is formed almost entirely of the frontal process of the zygomatic bone.

• The infraorbital margin is formed by the zygomatic bone laterally and the maxilla medially.

• The medial orbital margin is formed superiorly by the frontal bone and inferiorly by the lacrimal crest of the frontal process of the maxilla.
• This margin is distinct in its inferior half only.

The Paranasal Sinuses

• These sinuses are air-filled extensions of the respiratory part of the nasal cavity.
• They are in the following bones, frontal, ethmoid, sphenoid and the maxilla.

The Frontal Sinuses

• These are located between the outer and inner tables of the frontal bone, posterior to the superciliary arches.

The Ethmoidal Sinuses

• These comprise of several small cavities, called ethmoidal air cells, within the ethmoidal labyrinth (G. labyrinthos, a maze) of the lateral mass of the ethmoid bone.

The Sphenoidal Sinuses

• These occupy a variable amount in the body of the sphenoid bone and may extend into the wings.

The Maxillary Sinuses

• These are the largest pair of paranasal sinuses.
• They are pyramidal-shaped cavities that may occupy the entire bodies of the maxillae.

ENDOCRINE

Endocrine glands have no ducts

They secrete into the blood from where the secretion (hormone) reaches a target cell

The following is a list of endocrine glands:

• Hypophysis
• Thyroid
• Parathyroid
• Adrenals
• Islets of Langerhans
• Pineal
• Gonads

Hypophysis: Develops from oral ectoderm and nerve tissue,  The oral part forms an upgrowth with an invagination (Rathke's pouch) The nervous part grows from the floor of the diencephalon - staying intact .The oral part separates from the mouth

Ectoderm – adenohypophysis - pars tuberalis

- pars distalis

- pars intermedia .

Diencephalon – neurohypophysis   - pars nervosa .

- infundibulum

- median eminence

Rathke's pouch remains as Rathke's cysts

Pars Distalis: Forms 75% of the gland, The cells form cords,  with fenestrated capillaries in-between

2 Cell types:

Chromophobes :  50% of the cells, do not stain  lie in groups, they are resting chromophils

granules have been used

Chromophils: Stain

They can be subdivided according to their reaction with different stains

Acidophils (40%) :Cells have acidophilic granules in their cytoplasm. The cells are secretory.

They have a well developed EPR and Golgi apparatus.They have secretory granules.

subdivided into:

- Somatotropin cells: secrete somatotropin (growth hormone)

- Mammotropic cells:  secrete prolactin

Basophils (10%) :  These cells have basophilic granules in their cytoplasm and can be subdivided into:

Thyrotropin cells:  secrete thyroid - stimulating hormone (TSH)

Corticotrophin cells:  secrete adrenocorticotropic (ACTH)

Gonadotropic cells:  secrete two hormones:  Follicle stimulating hormone (FSH):

Stimulate follicle development and spermatogenesis

Luteinizing hormone (LH): Stimulate the formation of the corpus luteum and Leydig cells

Pars Tuberalis:  Cells lie around the infundibulum . It is continuous with the pars distalis

Cells are cuboidal with no granules. Their function is unknown

Pars Intermedia:  Poorly developed in the human. Follicles lined by cuboidal cells and filled with colloid are found Known as Rathke's cysts .There are also a few big basophilic cells

Their function is unknown

Pars Nervosa: Contains: - myelinated axons  pituicytes,  blood vessels

Axons:

The cell bodies of the axons lie in the supra-optic and paraventricular nuclei of the hypothalamus .From the cell bodies the axons go through the infundibulum forming the  hypothalamohypophyseal tract to end in the pars nervosa

 The axons have dilated blind endings filled with hormones (Herring bodies) coming from the cell bodies.

Two hormones are secreted:

Oxytoxin: - Cause contraction of the uterus

    - Cause contraction of the myoepithelial cells of the milkgland

    - The hormone is secreted by the paraventricular nuclei

Vasopressin :- Cause reabsorption of H2O in the kidney (also known as antidiuretic hormone ADH)  The hormone is secreted by the supraoptic nuclei.  A hypophyseal portal system exists

A primary capillary plexus of fenestrated capillaries form around the median eminence. Inhibitory hormones are secreted into these capillaries

The capillaries rejoin to form the portal veins that traverse the pituitary stalk

The portal veins break up into a secondary capillary plexus which lies close to the cells of the adenohypophysis

This portal system regulates the functions of the anterior pituitary function.

Pineal

Surrounded by pia which sends septae into the gland Cells are mainly pinealocytes and astroglial cells

Pinealocytes:Irregular shaped cells. with processes ending in flattened dilatations

Have a well developed smooth surfaced endoplasmic reticulum, Also a rough EPR not well developed, Lots of microtubules

Astroglial Cells: Elongated nucleus, Cells have long processes, They perform a supporting function

Hormones:

Melatonin - secreted during the night .suppress the onset of puberty

Serotonin - secreted during the day

In humans the pineal form concretions of calcified material called brain sand

Brain sand vary in size and number with age and is visible on X-rays

Mast cells are also found in the pineal and cause the high histamine contend of the gland

THYROID

Has a CT capsule that sends septae into the gland to divide it up into incomplete lobes and lobules. In the lobules are follicles, Follicles vary in size,  They are surrounded by surrounded by reticular CT and capillaries

Cells of the Follicle:

Follicular Cells :  Single layer of cuboidal cells,  lie around the colloid, Follicular cells can become columnar when very active, Nucleus  central, EPR has wide cisternae ,Golgi present

• microvilli on the free surface

Parafollicular Cells:  Also known as C-cells, Form part of the epithelium or form clusters between the follicles

- They never come into contact with the colloid

- Larger and stain less intensely than the follicular cells, Form 2% of the cells, Secrete calcitonin

Hormones: Thyroxine and thyriodothyronine - stimulate the metabolic rate, Calcitonin - lower the blood calcium

Parathyroid:

Has a CT capsule which send septae into the gland to divide it up into incomplete lobules, The CT contains fat which increase with age - may eventually be 50% of the gland, Glandular cells are arranged in cords

Glandular Cells:

Chief Cells:  Small cells so their nuclei lie close together, Rich in glycogen, Biggest omponent

Secrete parathyroid hormone - essential for life

Oxyphil Cells:Develop at puberty, Bigger than the chief cells, Nuclei are smaller, Acidophilic

Hormones:

Parathyroid hormone - regulate calcium and phosphate ions in the blood

ADRENAL

- Thick CT capsule that do not send septae into the gland

Cortex:

Has 3 layers

Zona glomerulosa: 15% of the cortex, Directly under the capsule, Cells are columnar or pyramidal,  Arranged in small groups or clusters, Wide fenestrated capillaries surround the clusters, Cells have an extensive smooth EPR

Zona Fasciculata: 78% of the cortex, Cells are arranged in cords ,1 to 2 cells wide perpendicular to the surface, Sinusoids lie between the cords, Cells are polyhedral with a central nucleus which is bigger than that of the zona glomerulosa, Lots of lipid in the cytoplasm cause the cells to stain lightly,  Cells have a well developed smooth and rough EPR

The mitochondria in the cells are round with tubular or vesicular cristae

Zona Reticularis:  7% of the cortex, Cells form a network of cords with wide capillaries in-between The mitochondria in the cells are more ofte6n elongated than that in the zona fasciculate  Degenerating cells with pyknotic nuclei are found.  Cells contain numerous large lipofuscin granules. Cells of the cortex do not store their secretions but form and secrete on demand.

Hormones:

3 Groups:

Glucocorticoids (e.g. cortisol) - have an affection on carbohydrate metabolism

Mineralocorticoid (e.g. aldosterone) - control water and electrolyte balans

Androgens (e.g. dehyroepiandrosterone) - not very important

Medulla:

- Cells are big and oval and lie in groups and cords around bloodvessels

- Oxidising agents stain the granules in these cells brown - cells are therefore called chromaffin cells

- Granules contain adrenaline or non-adrernalin

- A few parasympathetic ganglion cells are also present

Hormones:

- Adrenaline - increase oxygen uptake

- increase blood pressure

- Noradrenaline - maintain blood pressure

Blood Supply:

- Blood vessel enter from the capsule to form the wide capillaries

- They flow into venules that form a central vein

- Between the endothelium of the capillaries and the glandular cells there is a subendothelial

- space.

- The glandular cells have microvilli protruding into this space.

ISLES OF LANGERHANS

Endocrine part of pancreas.  The isles are round clusters in the exocrine tissue

- 100 - 200 µm

Islands consists of slightly stained polygonal or rounded cells,  The cells are separated by fenestrated capillaries

- Autonomic nerve fibres innervate the blood vessels and the island cells

- 4 different cell types have been described

A cells : 20% of the cells,  Bigger than B cells, Lie at the periphery, Have secretory granules ,Contain glucagon

B cells :  80%,  Lie in the centre of the island,  The cells are small with granules which are crystals,  Granules are formed by insulin

D cells :  Not numerous, Membrane bound granules, Store somatostatin (inhibit somatotropin)

F cells :  Have membrane bound granules,  Store pancreatic polypeptide, The hormone inhibits pancreatic exocrine secretion