Hsf&d Neck, Pharynx And Larynx

Front 1

Describe the organization of the neck and how the different fascial layers surrounds these compartments. What are their clinical significance?

Back 1

---all compartments are covered by investing fascia: forms largest compartment---
Visceral compartment: anterior
---contains: pharynx, trachea, esophagus, thryoid/parathryoid glands
---pretracheal layer: collection of fascias around trachea, esophagus and thryoid gland
Vertebral compartment: posterior
---contains: cervical vertebrae, spinal cord, cervical nerves and muscles associated with vertebral column
---prevertebral layer: surrounds vertebral column and deep muscles surrounding it; extends to cover brachial plexus/subclavian artery - axillary sheath
Vascular compartments: lateral (on each side)
---contains: major blood vessels and vagus nerve
---carotid sheaths (receive contribution from other layers) surround the neurovascular bundles

Clinical:
---between fascial layers are spaces that provide conduit fro spread of infections from neck to mediastinum
---pretracheal space: (between investing fascia and pretracheal) passing between neck and anterior/superior mediastinum
---retropharyngeal space: (betweeen pretracheal and prevertebral) from base of skull to posterior/superior mediastinum
---third space: (within prevertebral layer) base of skull through posterior mediastinum to diaphragm

Front 2

Describe the anatomical organization of the anterior triangle of the neck.

Back 2

Outlined by anterior border of sternocleidomastoid muscle laterally, inferior border of mandible superiorly and midline of neck medially
---muscles superior to hyoid are suprahyoid (stylohyoid, digastric, mylohyoid and geniohyoid)
---muscles inferior to hyoid are infrahyoid (omohyoid, sternohyoid, thyrohyoid and sternothyroid)

Front 3

Identify the suprahyoid muscles, their functions and innervation.

Back 3

Stylohyoid:
---pulls hyoid bone upward in posterosuperior direction
---facial nerve (VII)
Digastric:
---Anterior belly: opens mouth by lowering mandible, raise hyoid bone
---mandibular nerve (V3)
---Posterior belly: pulls hyoid upward and back
---facial nerve (VII)
Mylohyoid:
---support and elevation of floor of mouth; elevation of hyoid
---mandibular nerve (V3)
Geniohyoid:
---fixed mandible elevates and pulls hyoid forward; fixed hyoid pulls mandible downward and inward
---branch from anterior C1 (carried along hypoglossus (XII))

Front 4

Identify the infrahyoid muscles, their functions and innervation.

Back 4

Sternohyoid:
---depresses hyoid after swallowing
---anterior rami of C1-3 through ansa cervicalis
Omohyoid:
---depresses and fixes hyoid
---anterior rami of C1-3 through ansa cervicalis
Thyrohyoid:
---depresses hyoid, but when hyoid is fixed raises larynx
---branch of C1, carried by hypoglossus (XII)
Sternothyroid:
---draws larynx (thyroid cartilage) downward
---anterior rami of C1-3 through ansa cervicalis

Front 5

Identify and describe the course of the carotid arteries and their branches in the neck. What do they branches supply?

Back 5

Common carotid arteries:
---right: originated from brachiocephalic trunk posterior to sternoclavicular joint and is entirely in the neck
---left: originates in thorax as direct branch from aorta
---both ascend lateral to trachea and divide into internal/external carotid arteries near superior edge of thyroid cartilage
---at bifurcation, common carotid/internal carotid are dilated (carotid sinus/body); contains receptors to monitor blood pressure (innervated by glossopharyngeal IX) and receptors for blood chemistry/oxygen (innervated by glossopharyngeal IX/vagus X)

Internal carotid: ascends towards base of skull, no branching in neck; enters cranial cavity through carotid canal

External carotid: branches in order, after bifurcation
---superior thyroid artery: thyrohyoid muscle, internal structure of the larynx, sternocleidomastoid and cricothyroid muscles, thyroid gland
---ascending pharyngeal artery: pharyngeal constrictors and stylopharyngeus muscle, palate, tonsil, pharyngotympanic tube, meninges in posterior cranial fossa
---lingual artery: muscles of tongue, palatine tonsil, soft palate epiglottis, floor of mouth, sublingual gland
---facial artery: all structures of face from inferior border of mandible anterior to masseter muscle to medial corner of eye, soft palate, palatine tonsil, pharyngotympanic tube, submandibular gland
---occipital artery: sternocleiodmastoid muscle, meninges in posterior cranial fossa, mastoid cells, deep muscles of back, posterior scalp
---posterior auricular artery: parotid gland and nearby muscles, external ear and scalp posterior to ear, middle/inner ear structures
---superficial temporal artery: parotid gland and duct, masseter, lateral face, anterior part of external ear, temporalis, parietal/temporal fossae
---maxillary artery: external acoustic meatus, lateral/medial surface of tympanic membrane, temporomandibular joint, dura mater on lateral wall of skull/inner table of cranial bones, trigeminal ganglion and surrounding dura, mylohyoid muslce, mandibular teeth, skin on chin, temporalis, outer table in temporal fossa, structures in infratemporal fossa, maxillary sinus, upper teeth/gingivae, infra-orbital skin, palate, roof of pharynx, nasal cavity

Front 6

Describe the location and course of the major cranial nerves in the anterior triangle, their important branches and general functions.

Back 6

***Facial nerve (VII):
---branches innervate posterior belly of digastric, stylohyoid and platysma (which overlies anterior triangle)

Glossopharyngeal nerve (IX):
---leaves cavity from jugular foramen, passes between internal carotid artery/internal jugular vein posterior to styloid process/muscles, then anterior between internal/external carotid arteries to reach base of tongue/palatine tonsil
---innervates stylopharyngeus muscle, sends branch to carotid sinus, sensory branches to pharynx

Vagus nerve (X):
---exits cavity through jugular foramen, between glossopharyngeal/accessory nerves, descends medial to internal jugular vein in carotid sheath
---branches: motor to pharynx, to carotid body, superior laryngeal nerve - divides into internal/external branches, and cardiac branch

***Accessory nerve (XI):
---exits most posterior from jugular foramen, descends medial to internal jugular, passes posterior/downward to sternocleidomastoid and trapezius

Hypoglossus nerve (XII):
---leaves cavity through hypoglossal canal, descends medial to internal jugular vein, hooks around occipital artery towards posterior belly of digastric and disappears deep to mylohyoid
---supplies tongue, does not give off branches in anterior triangle

Front 7

Describe the location and course of branches of the spinal nerves in the anterior triangle and their general functions.

Back 7

Cervical plexus:
---transverse cervical nerve: anterior rami of C2-3, emerges beneath sternocleidomastoid, loops around it and crosses anteriorly; provides cutaneous innervation

Ansa cervicalis:
---loop of nerve fibers from C1-3; C1 forms superior root - innervates superior belly of omohyoid, upper parts of sternohyoid/sternothyroid; C2-3 form inferior root - innervates inferior belly of omohyoid, lower parts of sternohyoid/sternothyroid

Front 8

Describe the organization of the thyroid and parathyroid glands, their neurovascular supply and their relationship to other structures.

Back 8

Endocrine glands:
---thyroid: large, unpaired
---parathyroid: small, usually four on posterior surface of thyroid

Thyroid: two lateral lobes connected by isthmus, anterior to trachea
---Blood supply: superior thyroid artery (from external carotid) - branches: anterior/posterior glandular, anastomoses with opposite side and inferior thyroid; inferior thyroid artery (from thyrocervical trunk) - branches: inferior anastomoses with posterior superior thyroid artery
---venous: superior thyroid vein (drains area by superior thyroid artery) and middle/inferior thyroid veins to internal jugular (superior/middle) and brachiocephalic veins
---Innervation: recurrent laryngeal nerves (vagus X)

Parathyroid: two pairs of superior/inferior glands
---Blood supply: inferior thyroid artery (from thyrocervical trunk)
---venous: follows thyroid drainage
---Innervation: same as thyroid

Front 9

Describe the attachments, actions and innervation of the sternocleidomastoid muscle

Back 9

Sternocleidomastoid: attaches to manubrium of sternum and lateral 1/2 of superior nuchal line
---Function:
---bilateral: draw head forward
---unilateral: tilt head toward shoulder on same side, rotating face towards opposite side
---Innervation: accessory nerve (XI) and branches of anterior rami C2-4

Front 10

Describe the scalene muscles, their function and innervation. What is their relationship to adjacent nerves and blood vessels? What are consequences of hypertrophy?

Back 10

Anterior: elevate rib I, anterior rami of C4-7
Middle: elevate rib I, anterior rami of C3-7
Posterior: elevate rib II, anterior rami of C5-7

Brachial plexus and the subclavian artery pass between anterior and middle scalenes
---if anterior/middle hypertrophy, these nerves/vessels will be compromised

Front 11

Describe the origin, course and function of the major vascular structures of the posterior triangle of the neck.

Back 11

External jugular vein:
---most superficial, forms near angle of mandible, crosses sternocleidomastoid and descends vertically, ending in subclavian vein
---receives transverse cervical, suprascapular and anterior jugular veins

Transverse cervical artery:
---branches from thyrocervical trunk, passes laterally/posteriorly to anterior scalene/brachial plexus to reach trapezius where is branches
---superficial: continues on deep surface of trapezius
---deep: continues on deep surface of rhomboids near medial scapula

Suprascapular artery:
---branch of thyrocervical trunk, passes laterally and downward, to be posterior to clavicle, and distributes branches to muscles on posterior scapula

Front 12

Describe the origin and function of the cervical plexus and its major branches, as well as the spinal accessory nerve in the posterior triangle of the neck.

Back 12

Cervical plexus: C1-C4
---Muscular (deep):
---phrenic nerve (C3-5): supplies diaphragm (sensory/motor); runs on anterior surface of anterior scalene
---branches supply rectus capitus anterior/lateralis, longus colli/capitus
---contributes to formation of ansa cervicalis (C1-3) to innervate infrahyoid muscles

---Cutaneous (superficial):
---lesser occipital (C2): ascends along posterior border of SCM, supplies skin of neck/scalp posterior to ear
---greater auricular (C2-3): emerges along posterior border of SCM and ascends to base of ear, supplying skin of parotid region, ear, mastoid area
---transverse cervical (C2-3): passes around SCM, crossing anterior/horizontally to supply lateral/anterior neck
---supraclavicular nerves (C3-4): group that descend over clavicle, supplying skin over clavicle and shoulder to rib II

Spinal accessory nerve (XI):
---exits through jugular foramen, passes deep to SCM, innervates it and continues towards trapezius to innervate it

Front 13

Describe the organization and boundaries of the pharynx and their sensory innervation.

Back 13

Nasopharynx: respiratory function
---superior to soft palate and posterior extension of nasal cavities
---maxillary division (V2) of trigeminal and glossopharyngeal nerves
Oropharynx: digestive function
---from soft palate to epiglottis with anterior boundary of palatoglossal arches
---glossopharyngeal nerve
Laryngopharynx: respiratory and digestive function
---lies posterior to larynx from epiglottis to cricoid cartilage and includes middle/inferior constrictor muscles
---glossopharyngeal and vagus nerves

Front 14

Describe the arrangement of the pharyngeal constrictor muscles and their innervation.

Back 14

Three on each side, contribute to pharyngeal wall; when contract sequentially, facilitate swallowing
---Superior, middle and posterior
---vagus nerve (X)

Front 15

Describe the function and innervation of the longitudinal muscles of the pharynx.

Back 15

Stylopharyngeus: elevate pharynx
---glossopharyngeal
Salpingopharyngeus: elevates pharynx
---vagus
Palatopharyngeus: elevates pharynx; closure of oropharyngeal isthmus
---vagus

During swallowing, pull pharyngeal wall up and over bolus of food moving through pharynx to esophagus

Front 16

Describe the course of the subclavian artery and its branches in the neck.

Back 16

Subclavian: arch upward out of thorax to enter root of neck and become axillary artery as it travels towards the arm
---right: starts as a terminal branch of the brachiocephalic trunk
---left: is a direct branch from the aortic arch

Branches:
---vertebral artery: first branch, medial to anterior scalene, ascends to enter transverse foramen of C VI vertebrae, continuing in the foramina until C I, where it enters the foramen magnum of the skull
---thyrocervical trunk: second branch, medial to anterior scalene and divides into three branches
---inferior thyroid artery: superior continuation, anterior to anterior scalene, supplies posterior portion of thyroid gland; gives off branch (ascending cervical artery) to supply prevertebral muscles/spinal cord
---transverse cervical artery: middle branch, passes laterally, continuing towards deep surface of trapezius
---suprascapular artery: lowest branch, passes laterally towards the scapula to enter the supraspinatus fossa
---internal thoracic artery: third branch, from inferior edge and descends towards the thoracic cavity
---costocervical trunk: final branch in root of neck, ascends and passes posterior and gives off branches (deep cervical/supreme intercostal) that anastomose with occipital/form posterior superior intercostal arteries
---left: arises medial to anterior scalene
---right: arises from second part of subclavian, higher than left

Front 17

Describe the inputs and outputs of the superior cervical ganglion. What are the targets and how do these axons reach their destination?

Front 18

Describe the inputs and outputs of the superior cervical ganglion. What are the targets and how do these axons reach their destination?

Back 18

Preganglionic sympathetic fibers from upper thoracic spinal cord levels synapse with postganglionic sympathetic fibers in the ganglion, which are then distributed to:
---internal carotid and external carotid arteries, forming plexuses around them
---cervical spinal nerves C1-4 through gray communicating rami
---pharynx
---heart as superior cardiac nerves

***postganglionic fibers follow arteries to reach their destinations***

Front 19

Describe the inputs and outputs of the superior cervical ganglion. What are the targets and how do these axons reach their destination?

Back 19

Preganglionic sympathetic fibers from upper thoracic spinal cord levels synapse with postganglionic sympathetic fibers in the ganglion, which are then distributed to:
---internal carotid and external carotid arteries, forming plexuses around them
---cervical spinal nerves C1-4 through gray communicating rami
---pharynx
---heart as superior cardiac nerves

***postganglionic fibers follow arteries to reach their destinations***

Front 20

Describe the pathway of the phrenic and vagus nerves in the neck and their relationship to other structures.

Back 20

Phrenic:
---branches of cervical plexus (C3-5), pass around upper lateral border of anterior scalene, continues inferiorly on anterior surface of anterior scalene until it passes between the subclavian vein and artery to enter the thorax

Vagus:
---descends through neck in carotid sheath, posterior to/between common carotid artery and internal jugular vein, then passes between subclavian artery/vein to enter thorax
---gives off cardiac branches that pass posterior to subclavian artery to enter thorax
---also branches into right/left recurrent laryngeal nerves to supply larynx

Front 21

Describe the boundaries of the subsites of the larynx.

Back 21

Supraglottic larynx:
---portion above the vocal folds; contains false cords, laryngeal ventricles, epiglottis and aryepiglottic folds

Glottic larynx:
---consists of vocal cords

Subglottic larynx:
---portion below vocal cords, continuous with upper trachea

Front 22

Describe the arrangement of the major laryngeal cartilages and their relationship to the vocal cords.

Back 22

Cricoid cartilage:
---most inferior, encircles airway; shaped like a signet ring
Thyroid cartilage:
---largest, formed by right/left lamina that are separated posteriorly, converge anteriorly; creates Adam's apple
Epiglottis:
---leaf-shaped, attached by stem to posterior aspect of thyroid cartilage
Arytenoid cartilage:
---two pyramid-shaped, has elongated base (vocal process) for attachment of vocal ligament

Vocal folds:
---lie inferior to vestibular folds (false vocal cords), which are attached to the aryteniod cartilage

Front 23

Describe how the appearance of the vocal folds differs during inspiration and during speech.

Back 23

Inspiration:
---quiet respiration: laryngeal inlet, vestibule, rima vestibuli/glottidis are open and arytenoid cartilages are abducted
---forced inspiration: arytenoid cartilages rotate laterally, vocal folds are abducted and diameter of airway increases

Speech:
---arytenoid cartilages and vocal folds are adducted, air is force through closed rima glottidis; causes vocal folds to vibrate against one another and produce sounds

Front 24

Describe the motor and sensory innervation of the larynx.

Back 24

Controlled by two branches of the vagus nerve (X):
---superior laryngeal nerves: divides into two branches
---external: supplies inferior constrictor of pharynx and cricothyroid muscle
---internal: mainly sensory, supplies laryngeal cavity down to vocal folds
---recurrent laryngeal nerves: sensory to laryngeal cavity below level of vocal folds; motor to all intrinsic muscles of larynx except cricothyroid

Front 25

Describe the function and innervation of the posterior cricoarytenoid muscle and why it is important to the vocal folds.

Back 25

Posterior cricoarytenoid:
---abduction and external rotation of arytenoid cartilage (primary abductors of vocal folds); open rima glottidis
---recurrent laryngeal branch of vagus

Importance:
---abducts vocal folds and widens rima glottidis to increase the diameter of laryngeal airway and allow for forced inspiration

Front 26

List the common features and components of a typical pharyngeal arch.

Back 26

Pharyngeal arches: 5 total
---formed from core of mesenchymal (mesoderm and neural crest cells) tissue covered by ectoderm and lined by endoderm
---mesoderm forms muscles and arteries
---neural crest cells migrate into arches/face where differentiate into connective tissues, nerves, bone of face and neck
---ectodermal thickenings (placodes) assist neural crest cells in formation of cranial nerves V, VII, IX, X
---aortic arch, cartilage bar and myoblasts develop within each pharyngeal arch (not all persist)
---the aortic arch blood vessels transmit blood from the ventrally located heart around the pharynx to the dorsal aorta
---each arch is innervated by single cranial nerve (or major branch)

Pharyngeal apparatus:
---pharyngeal arches: (1-4, 6) contains somitomeric mesoderm and neural crest cells
---pharyngeal pouches: (1-4) evaginations of endoderm from foregut
---pharyngeal clefts: (1-4) invaginations of ectoderm between each arch
---pharyngeal membranes: (1-4) consist of ectoderm, intervening mesoderm/neural crest cells and endoderm between each arch

Front 27

Describe the nerve that innervates the first pharyngeal arch and the musculoskeletal structures derived from its cells

Back 27

Nerve:
---trigeminal CN V (but not ophthalmic division)

Derivatives:
---Muscles: muscles of mastication (temporalis, masseter, medial/lateral pterygoids), mylohyoid, anterior belly of digastric, tensor tympani, tensor veli palatini
---Skeletal: malleus, incus
---Ligaments: anterior ligament of malleus, sphenomandibular ligament

Front 28

Describe the nerve that innervates the second pharyngeal arch and the musculoskeletal structures derived from its cells.

Back 28

Nerve:
---Facial CN VII

Derivatives:
---Muscles: muscles of facial expression (buccinator, auricularis, frontalis, platysma, orbicularis oculi, orbicularis oris), stapedius, stylohyoid, posterior belly of digastric
---Skeletal: stapes, styloid process, lesser cornu of hyoid, upper part of body of hyoid
---Ligaments: stylohyoid ligament

Front 29

Describe the nerve that innervates the third pharyngeal arch and the musculoskeletal structures that are derived from its cells.

Back 29

Nerve:
---Glosspharyngeal CN IX

Derivatives:
---Muscles: stylopharyngeus
---Skeletal: greater cornu of hyoid, lower part of body of hyoid

Front 30

Describe the nerves that innervate the fourth* and sixth pharyngeal arches and the musculoskeletal structures that are derived from its cells.

Back 30

Nerves:
---superior laryngeal branch of vagus (CN X)*
---recurrent laryngeal branch of vagus (CN X)

Derivatives:
---Muscles: cricothyroid*, levator veli palatini*, constrictors of pharynx*, intrinsic muscles of larynx, striated muscles of esophagus
---Skeletal: thyroid cartilage*, cricoid cartilage*, arytenoid cartilage, corniculate cartilage, cuneiform cartilage

Front 31

Describe the derivatives of the pharyngeal pouches.

Back 31

1st pouch:
---primitive tympanic or middle ear cavity, auditory tube
2nd pouch:
---palatine tonsil
3rd pouch:
---dorsal wing - inferior parathyroid gland; ventral wing - thymus
4th pouch:
---dorsal - superior parathyroid gland; ventral - ultimobranchial body

***all endodermal derivatives***

Front 32

Describe the migration of the thymus, parathyroid glands and ultimobranchial body.

Back 32

Inferior parathyroid gland and thymus gland lose their connection with the pharyngeal wall > thymus migrates caudally/medially, pulling inferior parathyroid with it > superior parathyroid gland loses contact and attaches to dorsal surface of migrating thyroid gland > ultimobranchial body embeds in thyroid gland to form parafollicular or C cells (secrete calcitonin to regulate blood calcium)

Front 33

Describe the development of the tongue.

Back 33

Develops from pharyngeal arches 1-4
---during development, 2nd (hyoid) arch is overgrown by the 3rd arch; foramen cecum forms at contact point between median tongue bud and the third arch
---leads to anterior 2/3 of tongue receiving sensory information from lingual branch of V3 (taste by facial) and posterior 1/3 from glossopharyngeal
---epiglottis and below are innervated by vagus

Front 34

Describe the development of the thyroid gland.

Back 34

Originates as an endodermal proliferation at tip of foramen cecum of developing tongue and migrates inferiorly
---thyroglossal duct connects thyroid to foramen cecum until wk 5
---two lobes connected by isthmus

Front 35

Which congenital defect occurred during abnormal development?

Back 35

Thyroglossal cysts:
---remnant of thyroglossal duct: may persist as fibrous stand, rarely as a fistula; cysts may be found along path of thyroid descent
---variations will be found midline

Front 36

What congenital defect has occurred due to abnormal development?

Back 36

Cervical sinus:
---second arch grows posteriorly and covers smaller arches; normally the surfaces fuse and obliterate the sinus
---if doesn't happen, cervical cysts or fistulas result
---present laterally, anterior to SCM and can be internal or external

Front 37

Describe the development of the external ear.

Back 37

Develops from 6 tissue accumulations (auricular hillocks) that appear on the 1st and 2nd arches on either side of 1st ectodermal cleft (site of future external auditory meatus)
---gradually merge into typical shape of auricle by middle of fetal life

Front 38

Describe the anomalies that can occur during external ear development.

Back 38

Problems with hillocks can lead to conductive hearing loss (sound waves cannot pass through ear canal)
---90% of hearing loss is non-conductive (inner ear/auditory nerve)
---hearing loss can result from mutations (connexin 26) or environmental factors (aminoglycosides, noise)
---hearing loss is present at birth in 1:300 babies (one of most common birth defects)

Front 39

Describe the development of the internal ear.

Back 39

Development:
---thickened otic placode (ectoderm) at dorsal end of 2nd pharyngeal arch invaginates to form otic pit
---otic pit pinches off from surface ectoderm and becomes otic vesicle (future inner ear)
---otic vesicle transforms into membranous labyrinth of inner ear
---semicircular canals form from one end (superior) of elongating otic vesicle; other end (inferior) turns 2.5 times to form cochlear portion
---cells adjacent to developing labyrinth differentiate into ganglion cells of VIII (formed by ectoderm and neural crest cells)

Front 40

Describe the development of the middle ear.

Back 40

Consists of tympanic cavity, auditory tube and ossicles
---tympanic cavity: derived from endoderm of pharyngeal pouch 1
---distal tubotympanic recess becomes tympanic cavity, proximal part forms auditory tube
---ossicles develop from cartilage of pharyngeal arch 1 (malleus/incus) and arch 2 (stapes
---handle of malleus contacts tympanic membrane (pharyngeal membrane 1)
---stapes contacts membrane of oval window

---middle ear cavity and ossicles covered by epithelium that is continuous with nasopharynx from auditory tube

Front 41

Describe the function of the endocrine system - what is the role of hormones, by what mechanisms to they act and what processes control their release?

Back 41

Function:
---maintenance of internal environment: water balance, metabolism, glucose/calcium levels
---integration and regulation of growth/development
---response to stress
---control and maintenance of sexual reproduction

Hormones: 3 types - produced in endocrine organ
---endocrine: secreted into the blood and goes to distant site
---paracrine: produced in cell and affects neighboring cell in same organ/tissue
---autocrine: cell produces hormone that affects itself

Processes:
---steriod hormones: longest half life (4min-3hr); lipid soluble, released from blood and passes directly through cell membrane, attaches to cytoplasmic receptor and causes changes in gene activity, which alters enzyme activity/cell response
---Amine/polypeptide hormones: amine - shortest half life (2-3min)/polypeptide - half life (4-40min); are first messengers, attach to receptor on cell membrane to activate second messenger, which alters enzyme activity/cell response

Front 42

Describe the anterior and posterior pituitary.

Back 42

Pituitary: considered master endocrine gland because it controls the function of other organs
---Anterior: formed from the hypophyseal pouch within the stomodeum/oral ectoderm, does not have direct contact with the hypothalamus; stimulation/inhibition passes from hypothalamus via the hypophyseal portal system
---produces/secretes hormones that affect other endocrine organs
---Posterior: formed from neurohypophyseal bud from within the brain/neuroectoderm, maintaining direct connection with hypothalamus via infindibulum; directly receives hormones produced in hypothalamus and releases them

Front 43

Describe the hypothalamic control of the endocrine organs.

Back 43

Front 44

Describe the histology of the pituitary gland.

Back 44

Anterior lobe: stains darker
---contains:
---acidophils: stain dark, secrete growth hormone (somatotrophs) and prolactin (mamotrophs)
---basophils: stain light, secrete TSH (thyrotrophs), FSH/LH (gonadotrophs) and ACTH (corticotrophs)
---chromophobes: cytoplasm doesn't stain; non-functional, going through apoptosis

Posterior: stains lighter
---contains:
---neurosecretory cells: from hypothalamus (wavy lines) that secrete oxytocin and ADH
---pituicytes: glial (support) cells, darker round spots

Front 45

Describe the function of the hormones secreted by the pituitary gland.

Back 45

Anterior:
---Growth hormone (somatotroph; acidophil): targets liver; function/product - IGF-1, bone/soft tissue growth
---Prolactin (mamotroph; acidophil): targets mammary gland; function/product - lactation
---Thyroid stimulating hormone [TSH] (thyrotroph; basophil): targets thyroid gland; function/product - T3/T4, regulation of cellular metabolism
---Follicle stimulating hormone [FSH]/Luteinizing hormone [LH] (gonadotrophs; basophil): targets ovary (follicle cells)/testis (seminferous epithelium and leydig cells); function/products - progesterone/estrogen/testosterone, follicle development, spermatogenesis
---Adrenocorticotrophic hormone [ACTH] (corticotroph; basophil): targets adrenal cortex; function/product - cortisol, regulation of metabolism and immune response

Posterior:
---Oxytocin: targets uterus, mammary gland; function/product - uterine contraction, milk ejection reflex
---Antidiuretic hormone [ADH]: targets kidneys, blood vessels; function/product - water reabsorption, vasoconstriction/increased blood pressure

Front 46

Describe the feed-forward and feed-back systems.

Back 46

Example: Hypothalamus-pituitary-thyroid axis
---Stimulus: low body temperature > hypothalamus releases thyrotropin releasing hormone (TRH) > anterior pituitary releases thyroid stimulating hormone (TSH) > follicular growth is stimulated and thyroid hormone (TH - T3/T4) is synthesized and released > metabolism is increased, basal body temperature is increased > increase in body temperature stops stimulus, inhibiting TRH production/secretion; TH also inhibits TSH production/secretion

Front 47

Describe the hypophyseal portal system and its involvement in the regulation of pituitary hormone release.

Back 47

Receives blood from superior/inferior hypophyseal arteries
---Consists of two successive capillary networks, one around each anterior/posterior portion, which drain into collecting hypophyseal veins
---carries neuropeptides from neurons in median eminence to anterior portion to stimulate/inhibit hormone release by its endocrine cells
---neurons from supraoptic/paraventricular nuclei extend axons directly into the posterior pituitary to secrete peptides that are carried by the capillaries to distal target cells

Front 48

Describe the function and histological structure of the thyroid gland.

Back 48

Function:
---cell growth
---cell differentiation
---control of basal metabolic rate and O2 consumption
---protein, lipid and carbohydrate metabolism

Structure:
---contains follicles, which are filled with colloid and are outlined by follicular cells; surrounding are parafollicular (C) cells

Front 49

Describe thyroid hormone production.

Back 49

Occurs in 2 phases:
---Exocrine phase:
1. TSH receptor stimulation 2. uptake of iodide from blood via ATP-dependent pump 3. diffusion of iodide through cell 4. synthesis of thyroglobulin homodimer; exocytosis into colloid 5. oxidation of iodide by thyroid peroxidase bound to apical plasma membrane 6. transfer of iodine to tyrosyl residues of thyroglobulin 7. storage of iodothyroglobulin in colloid

---Endocrine phase:
1. TSH receptor stimulation 2. uptake of colloid droplet 3. fusion of droplet with lysosome and enzymatic degradation of iodothyroglobin to T3 (triiodothyronine) and T4 (thyroxine) 4. release of T3 and T4 into bloodstream and interaction with binding proteins
***T3: active form, T1/2 = 18 hrs
***T4: inactive form, T1/2 = 5-7 days
---mostly T4 is made during thyroid, and is activated peripherally by diiodinate to make T3

Front 50

Describe the role of calcitonin in calcium homeostasis.

Back 50

Produced by parafollicular cells in thyroid gland
---during high blood calcium, cells secrete calcitonin, which affects kidney/gut for increased calcium excretion as well as activates osteoclast calcitonin receptors to immobilize/retract osteoclasts from bone surface, which decreases bone turnover and decreases plasma calcium
---negative feed-back from decreasing plasma calcium inhibits calcitonin secretion

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Describe the function and histological structure of parathyroid glands.

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There are usually four glands (two pair) on the back of the thyroid gland
---composed mainly of principle cells, which secrete parathyroid hormone
---during low blood calcium, PTH affects kidney/gut to increase calcium absorption as well as activate osteoblasts and stimulate osteoclast formation to increase bone turnover and increase plasma calcium (which provides negative feedback to inhibit PTH)
---also contains some oxyphil cells (lighter): non-functional, going through apoptosis

Front 52

Describe the function and histological structure of the adrenal gland.

Back 52

Primary function:
---maintain homeostasis
---regulation of body's adaptive response to stress
---maintenance of body water, sodium and potassium balance
---control of blood pressure

Structure:
---Medulla: dark center, composed of chromaffin cells (originally neural crest cells) - produce epinephrine/norepinephrine (catecholamines); stimulated by acetylcholine from preganglionic sympathetic neurons; function - vasoconstriction, increased BP/HR and elevated blood glucose
---Cortex: three layers (dark, light, dark)
---zona glomerulosa (dark outer): produces aldosterone (mineralocorticoids); stimulated by increased plasma K+, angiotensin II, decreased plasma volume; function - increased reabsorption of ions/water, increased BP/blood volume, salt balance, Na+ reabsorption by DCT
---zona fasciculata (middle light): produces cortisol (glucocorticoids); stimulated by ACTH; function - carbohydrate metabolism, fat mobilization, protein catabolism in muscle, immune system suppression
---zona reticularis (inner dark): produces androstenedione, dehydroepiandrostene (steroid sex hormones); stimulated by ACTH; function - uncertain significance under normal conditions