4. The muscles and fasciae of the head and neck. The histology of the hypophysis. The development of the face.

4 Dec

4. The muscles and fasciae of the head and neck. The histology of the hypophysis. The development of the face.

Flash Cards:

Anatomy: The muscles and fasciae of the head and neck

Muscles of the Face:

These are mainly the muscles of facial expression. What are they? Look above at the flash cards, or at this one.

Sorry, I know it’s a bit unclear, but it’s the best I could find at the moment.

Muscles of Facial Expression:

General Info:

  • are subcutaneous, and very close to the surface
  • all innervated by CN VII = facial n.
  • develop from mesenchyme of 2nd pharyngeal arch – (Hence why that CN VII innervation makes sense)

1. Occipito-frontalis (Epicranialis) – elevate eyebrow,wrinkles forehead (surprise)

  • if you use just frontalis (frontal belly of epicranialis) = furrows eyebrows medially
  • use both bellies = lift eyebrows, move scalp

2. Orbicularis Oculi

  • has 3 parts: palpebral (just over the eyelid itself) = close eyes gently,
  • orbital (around the whole eye) = close eyes tightly, or used to squint
  • lacrimal (medially) = draws tears out, so capillaries can drain them
3. Auricularis m –
  • ant, mid, post. – not all people have this muscle
  • allows movement of the auricle, retract and elevate ear

4. Levator Labii Superioris m – elevate upper lip, dilate nares (disgust)

5. Zygomaticus Minor m – elevate upper lip

6. Zygomaticus Major m – draws angle of mouth up (smaller smile – like the fake one you give when you are in a bad mood)

7. Depressor Septi m – constricts nares

8. Risorius m – retracts angle of mouth more ( smile widely, a big cheesy grin)

9. Depresser Anguli Oris – depresses angle of mouth

10. Corrugater Supercili m – draws eyebrows down and medially (anger, frowning)

11. Procerus m – wrinkles skin over forehead (sadness)

12. Levator Labii superioris aleque nasi – elevate ala of nose, upper lip

13. Levator Anguli Oris m – elevate angle of mouth medially

14.Buccinator m – holds cheeks tight when blowing hard

  • named after the word for trumpet, so when someone can blow into a trumpet, without inflating their cheeks, they are using their buccinator m.
  • If you use only one, you can pull mouth to one side, like in a half-smile.

15. Orbicularis Oris – closes lips, and purses them (like for a kiss, or around a straw)

16. Depresser Labii inf m – pulls down lower lip

17. Mentalis m – elevates & protrudes lower lip, wrinkles chin

18. Nasalis m – pulls ala of nose towards septum, wrinkles nose (think the movie/show Bewitched)

  • Dilator naris m – open nostrils
  • Compresser naris m – constrict nostrils

19. Platysma – lowers mandible, can also help in frowning,  tenses skin of lower face and neck

To test yourself on m. of fascial expression: http://www.ivy-rose.co.uk/Topics/FacialMuscles.htm

For Muscles of Tongue, Palate, Pharynx, Larynx, etc – please refer to those topics in question. Those are technically muscles of the head & neck  too, but we doubt they are involved with this topic.

Fascia of Neck

  • Superficial Cervical fascia
    • subcutaneous CT
    • cutaneous n, a/v/lymph, superficial lymph nodes
    • enlcose platysma
  • Superficial (investing) layer of deep fascia
    • surround deeper parts of neck
    • encloses SCM & Trapezius m
    • also encloses the submandibular gland & makes fibrous sheat of parotid gland
    • has suprasternal space – ant jugular v, and arch of jugular v.
    • attached Sup = mandible, mastoid pr, ext occipital protuberance, sup nuchal line
    • Inf = acromion process, scapular spine, clavicle, manubrium
  • Prevert fascia of deep fascia
    • cylindrical & encloses vert column & m. w/ it
    • covers Scalene m & deep m of back
    • extends laterally into axillary sheath – has axillary a/v and brachial plexus
    • attaches to ext occipital protuberance & basilar part of occipital bone & cont w/ endothoracic fascia & ant longitudinal lig of vert
  • Carotid Sheath
    • Contents: Common & Int & Ext carotid a, Int jugular v, CN X, n to carotid sinus, deep cervical lymph nodes
    • DOES NOT contain SNS Trunk, which is post to Carotid sheath & ant to prevert fascia
    • blends w/ prevert, pretracheal investing layers & also attaches to base of skull
  • Pretracheal Fascia of Deep Fascia

    • invests larynx & trachea, esoph
    • encloses thryoid gland & contributes to carotid sheath formation
    • has thin musc layer of infrahyoid m
    • connects w/ Buccopharyngeal fascia superiorly
    • Sup = Thyroid & Cricoid cart
    • Inf = Pericardium
  • Buccopharyngeal fascia
    • covers buccinator m & pharynx
    • attached to pharyngeal tubercle & pterygomandibular raphe
  • Pharyngobasilar fascia
    • fibrous coat in wall of pharynx
    • b/w mucus mem & pharyngeal constrictor m

Superficial & Lat M of the Neck

  • Platysma – (CN  VII) – depress lower jaw, lip, and angle of mouth
  • SCM – (CN XI) – 1 of them, turns face to opposite side, bringing chin to opposite shoulder, w/ BOTH = flex head, raise thorax

Muscles of Posterior Triangle (will discuss later)

  • Splenius Capitis
  • Levator Scapulae
  • Scalenus m

Muscles of Anterior Triangle

Suprahyoid m:

  • Mylohyoid (Mylohyoid n of V3) – elevate hyoid & floor of mouth, lowers mandible, makes up floor of mouth
  • Geniohyoid (C1 via Hypoglossal n) – elevate hyoid and floor of mouth, rest above the mylohyoid
  • Stylohyoid (CN VII ) – elevate hyoid
  • Digastric (ant belly = Mylohyoid n of V3, post belly = CN VII) – elevate hyoid & floor of mouth, depresses mandible,

Remember that muscles that originate from 1st arch = CN V, and 2nd arch = CN VII

Infrahyoid M: all innervated by Ansa Cervicalis, except THYROHYOID (C1 via Hypoglossal n), together they anchor the hyoid bone, scapula, clavicle, and lower the hyoid bone and larynx for swallowing

Superficial muscles:

  • Sternohyoid m – depresses hyoid & larynx
  • Omohyoid m – depress and retracts hyoid & larynx

Deeper muscles:

  • Sternothyroid m – depresses thryroid cartilage and larynx, is wider and just underneath sternohyoid
  • Thyrohyoid m – depressed and retracts hyoid & larynx

Deep Neck Muscles:

Lat/Ant Vertebral muscles

Lat/Ant Vertebral muscles

Lateral Vertebral m

NOTE – Can mention Scalenus Tent, Hiatus, Subclavian a, Scaleno Tracheal Fossa here. See Flash Cards @ Beg of Topic.

  • Ant Scalene m (C5-C8 ) – elevate 1st rib, bend neck
    • From transv. process of C3-6 –> scalene tubercle of 1st rib
  • Mid Scalene m (C5-C8 ) – elevate 1st rib, bend neck
    • From transv. process of C2-7–> upper surface of 1st rib
  • Post Scalene m (C6-C8 ) – elevate 2nd rib, bend neck
    • From transv. process of C4-6 –> outer surface of 2nd rib

Ant Vertebral m

  • Longus Capitis (C1-4) – flex, rotate head
    • transv processes of C3-C6 –> inf surface of basilar part of occipital bone
  • Longus Colli – (C2-6) – flex, rotate head – NOTE same as longus cervicis
    • ant tubercle of atlas –> Bodies of T3 and transv processes of C3-C6
  • Rectus Capitis ant (C1-2) – flex, rotate head
  • Rectus Capitis lat (C1-2) – flex head laterally

SubOccipital & Deep Neck M

  • Suboccipital region flash card listed above, triangular region just below the occiput of the skull,
  • all muscles innervated by suboccipital n (C1)
  • Extend, rotate and flex head laterally.
  • Rectus capitis posterior major – spinous process of C2 –> lat part of inf nuchal line
  • Rectus capitis posterior minor – post tubercle of Atlas –> medial part of inf nuchal line
  • Obliques capitis superioris- spinous process of C1 –> medial part of inf nuchal line
  • Obliques capitis inferioris – transverse process of C1 –> occipital bone b/w nuchal lines

NOTE:  Layers in order in back m (That is, if you were to peel off the muscles layer by layer) – Trapezius, Semispinalis & Longissimus Capitis, Splenis Capitis, then these muscles, with the suboccipital triangle w.in them.

Suboccipital Triangle

Borders:

  • med = rectus capitis post major
  • lat = obliques capitis sup
  • inf = obliques capitis inf
  • roof = semispinalis m
  • floor = post atlanto-occipital membrane, post arch of atlas

Contents: Vertebral a/v, Suboccipital n. NOTE – KNOW PATHWAY OF VERTEBRAL A!!

In Aqua is the location of the Suboccipital Triangle

In Aqua is the location of the Suboccipital Triangle

Histology: Hypophysis.

Slide #31 Hypophysis *H&E

Structures to Identify:

  • adenohypophysis
  • neurohypophysis
  • pars distalis
  • pars intermedialis
  • pars tuberalis
  • pars nervosa
  • CT capsule
  • acidophils
  • basophils
  • chromophobes
  • capillaries
  • Herring bodies
  • Dura mater (may not be able to see) – dense CT
  • reticular fibers
  • brown pigment


General Info:

Hypophysis has 2 major subdivisions: ant lobe = adenohypophysis, post lobe = neurohypophysis
is located in sella turcica of sphenoid bone
connected by stalk (tuber cinerum) to base of brain (hypothalamus)


Adenohypophysis
– divided into 3 parts: pars distalis (most ant), pars tuberalis, pars intermedia
* Embryo: derived from invagination of ectoderm of oropharynx toward the brain = Rathke’s pouch, placode plate, becomes part of roof of oral cavity
Neural system in ant lobe:
since it does not develop from neural tissue, has rich a/v system that connects it w/ hypothalamus of brain via portal system
Neurons in hypothalamus synthesize hormones that have direct influence on cell functions of adenohypophysis
Axons of those neurons extend and terminate on 1st capillary bed of ant lobe – and then release hormones there

Pars distalis
– bulk of ant lobe
have clusters of cells w/ layers of fiber between them

contains 2 types of cells:
Chromophobes – inactive cells, euchromatic nucleus, pale cytoplasm

Chromophils
– active, hormone producing cells
2 types of them:

Acidophils (40%  of cells in ant lobe)
reddish pink = eosinophillic
2 types:

Somatotropes (GH cells) –

  • oval w/ round nucleus + eosinophillic vesicles in cytoplasm
  • (+) by Growth Hormone, (-) by somatostatin
  • GH secreted while sleeping, important to keep healthy cells in order for them to go thru mitosis
  • hypothalamus hormones regulate GH
  • NOTE – Targets of acidophillic cells (secrete hormones w/ general effect), are not endocrine cells


Lactotropes (PRL cells) –

  • large polygonal cells w/ eosinophillic vesicles of prolactin, oval central nuclei
  • (+) by TRH + VIP (synthesis secretion)
  • (-) by Dopamine – secretion


Basophilsbluish purple cytoplasm (all have round eccentric nucleus)

Corticotrophs (ACTH release)

  • polygonal, produce precursors of ACTH
  • (+) by CRH from hypothalamus

Gonadotropins (FSH + LH release)

  • regulated by GnRH (Gonadotropin releasing hormone) from hypothalamus
  • LH =
    • (+) production of corpus luteum
    • (+) testosterone secretion
  • FSH = stimulates spermatogenesis, follicle release


Thyrotropins
(TSH release) –

  • large stimulate thyroid gland production of thyroid hormones (T3 + T4)
  • regulated by TRH (Thyroid releasing hormone) from hypothalamus
  • acts on follicular cells of thyroid


Pars Intermedialis

  • surround small cystic cavities  representing residual lumen of Rathke’s pouch
  • lined by epitheloid cells w/ a/v outside of them
  • contain basophils + chromophobes in nests surrounding inner cavity = colloid
  • fluid filled colloid contains pre-hormones stored there
  • if need hormones, cells take back the pre-hormones , edit, then reject


Pars tuberalis

  • ext of ant lobe along pituitary stalk, highly vascular region
  • contains hypothalamus – hypophyseal portal system *talk about later*
  • cells form cellular columns, not clusters, but parallel rows of cells and fibers
  • To understand ant lobe:
    • need to know hormone regulation of hormone production
    • released by paracellular neurosecretory neurons in hypothalamus – regulates the hormone production of ant lobe
    • releasing factor – inc secretion
    • inhibiting factor – dec secretion


Posterior lobe = neurohypophysis

General Info:

Pituicytes

Pituicytes


is downgrowth of CNS
CNS has 2 cell types: neurons, glial cells

  • both are present in neurohypophysis
  • but glial cells called pituicytes here

NO cell bodies of neurons here, but yes, axons of them are present
cell bodies of neurons located in nuclei of hypothalamus, axons are longer and terminate in walls of sinusoids in post lobe

NOTE – axons carry hormones continously, but these are only released sporadically
so hormones need to be stored = in Herring bodies
NO HORMONES PRODUCED IN POST LOBE

Appearence: homogenous appearence, pinkins lines = axons
post lobe has 3 parts: median eminence, infundibulum, parsa nervosa

  1. Median eminence = @ base of hypothalamus
  2. Infundibulum = part of post lobe that extends up to hypothalamus
  3. Pars nervosa = largest part of post lobe

Pars Nervosa

  • contains secretory vesicle = Herring bodies – difficult to distinguish these from a/v
    • contain oxytocin, vasopressin from hypothalamus,fibroblasts, mast cells, pituicytes
  • Pituicytes = oval or round nuclei, and brown pigment in cytoplasmic vesicles
    • have processes to perivascular spaces = support
  • GFAP = glial fibrillary acidic protein –> specific intermediate filaments
  • Vasopressin (ADH)  – controls BP, contraction of smooth m in a./arterioles (VC = inc BP)
  • Oxytocin = neural stimulation
    • contraction of uterine smooth m during orgasm, mestruation, birth
    • contraction of myoepith cells in mammary gland –> milk ejection in lactation


Hypophyseal Portal (circulatory) System:

a “portal” system is any system of arterial supply that makes 2 arterial capillary beds
Originates from superior/inferior hypophyseal a

Sup Hypophyseal a

  • Superior hypophyseal a enters the hypophysis superiorly and supplies pars tuberalis, medial eminenece, conar skin
  • In the median eminence, it makes the primary (1st) capillary bed, then reforms and then makes a second capillary bed in the ant lobe itself
    • primary capillary bed is where the axons from hypothalamus neurons synapse and release hormones – the releasing/inhibiting factors mentioned earlier
    • the secondary capillary bed carries secretions of hypothalamus from med eminence –> infundibulum –> pars distalis
  • Once the releasing/inhibiting factors from hypothalamus are secreted into pars distalis, they will bind to specific receptors  on cells (chromophils) and cause them to either release or inhibit the release of the hormone they produce.

Inf Hypophyseal a

  • Inf hypophyseal a enters hypophysis inferiorly and supplies pars nervosa, makes ONE capillary bed – therefore not part, technically, of the portal system
  • unmyelinated axons from nuclei in hypothalamus release the oxytocin, ADH in the sinusoids of pars nervosa, and the hormones are then stored in nearby Herring bodies (@ axon terminals)


Sinusoids of pars nervosa  are fenestrated :

  • meaning they have a discontinous endothelium = allows transport b/w cells and sinusoids more free
  • they have NO BASEMENT MEMBRANE  – simply are resting on reticular fiber meshwork


Blood drains through hypophyseal v –> cavernous sinus –> systemic circulation
some thru short portal v from parts distalis –> pars nervosa –> hypothalamus


Slide #32 Hypophysis *AZAN (Azocarmine blue, anahiline red)

Structures to Identify:

  • dura mater = bluish dense CT
  • acidophils
  • basophils
  • reticular fibers
  • Herring bodies
  • brown pigmentation


Ant lobe

basophillic cells have complete blue cytoplasm
acidophillic cells are red
bluish line represent reticular fibers that belong to the CT stroma
v. homogenous look

Post lobe

bluish bodies and fibers are Herring bodies and their axons
brown pigmentation  = lipofusin – aging pigmentation in nerve tissue

Slide is designed to show Herring bodies (blue) + blood vessels (red) can be easily distinguished

Embryology:The development of the face.

  • @ 4th wk = facial prominences form, formed by 1st pharyngeal arch from neural crest cells
    • Maxillary prominence – forms lat to stomodeum, the primordial mouth
    • Mandibular prominence – forms caudal (below) to stomodeum
    • Frontonasal prominence – is a growth of mesenchyme that makes the upper border of the stomodeum = forehead, orbital area
    • On both sides of frontonasal prominences, there are forming 2 lateral thickenings of surface ectoderm = nasal placodes
  • @ 5th wk = nasal cavity and nasal projection begins to form (nose)
    • nasal placodes fold inwards (“invaginate”) to form nasal pits
    • around nasal pit, there is a ridge of tissue = nasal prominences.
    • *Picture a bowl – the actual bowl is nasal pit, and the rim of the bowl is the nasal prominences
    • The nasal prominences are split into lat & medial nasal prominences
  • @ 6th-7th wk = Maxillary prominences grow
    • the future cheeks/zygomatic areas are growing
    • this pushes the medial nasal prominences towards each other
    • maxillary prominences & med. nasal prominences fuses
    • This forms the upper lip
  • lower lip & jaw = mandibular prominences
  • Nose is formed by 5 areas
    • frontal part of frontonasal prominence = bridge of nose
    • 2 medial nasal prominences = crest of nose, tip
    • 2 lateral nasal prominences = sides, ala of nose
  • Nasolacrimal duct
    • starts off as groove b/w med/lat nasal prominences = nasolacrimal groove
    • the ectoderm in the floor of this groove – forms epithelial cord, that then detaches from the groove
    • this is the future duct – it will later open up into a canal
    • the upper part of it is widen up to form lacrimal sac
    • Deeper, med/lat nasal prominences fuse.
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