Head, special senses, and integument

week 2 content

the head includes what 2 parts

cranium (brain case)

face (mouth and nasal cavity)

the face will grow _____ from the cranium

outward

muscles of the head derived from

somtomeres

somitomeres

immature somites specific to head

pharyngeal arches are developed from

neural crest

what are pharyngeal arches

transient embryonic precursors that develop into other structures

what are pharyngeal arches composed of

all three germ layers (ectoderm, mesoderm, endoderm)

what adult structure does the 1st pharyngeal arch develop into

jaw bones

muscles of mastication

which cranial nerve is associated with the 1st pharyngeal arch

CN V (trigeminal nerve)

what adult structure does the 2nd pharyngeal arch develop into

hyoid bones

muscles of facial expression

what adult structure does the 3rd pharyngeal arch develop into

hyoid bones

pharyngeal muscles

what adult structure do the 4th and 6th pharyngeal arch develop into

larynx

laryngeal and pharyngeal muscles

which cranial nerve is associated with the 2nd pharyngeal arch

CN VII (facial nerve)

which cranial nerve is associated with the 3rd pharyngeal arch

CN IX (glossopharyngeal nerve)

which cranial nerve is associated with the 4th and 6th pharyngeal arch

CN X (vagus nerve)

what happens to the 5th pharyngeal arch

quickly regresses and disappears after forming

on each side of the forebrain, a portion forms an ____ ______

optic vesicle

how does the optic vesicle stay attached to the forebrain

through the optic stalk

neural crest cells and ectoderm form what visionary structures

globe, eyelids, conjunctiva

the optic vesicle forms what two things

optic cup and lens placode

what does the optic cup form

retina, ciliary body, iris

what structure becomes the lens

lens placode

the optic stalk becomes the

optic nerve

the outer ear (pinna and external ear canal) develop from

ectoderm of the first and second pharyngeal arches

the middle ear (bones of the middle ear and tympanic membrane) develop from

neural crest cells

the inner ear (vestibular apparatus) develops from the

otocyst

olfactory placode forms from the

neural plate ectoderm as the “nasal pit”

cells that line the caudal wall differentiate into olfactory neurons, which make up the

olfactory nerve (CN I)

Important: the olfactory placode and development of the olfactory nerve does not go through the

thalamus

olfaction goes directly to the

primary olfactory cortex in the brain

olfaction is one of the earliest senses to develop. What is a proposed suggestion for why this might be?

this sense is developed faster because of the need to sense essentials like danger, food, and mates

the surface epithelium develops into taste placode, which develops into

taste buds

chemoreceptor cells for taste rely on

detection of chemical molecules in the environment

chemoreceptor cells are present in both

taste and smell

chemoreceptor cells are processed in

closely related areas of the brain

chemoreceptor cells allow for

combined sensory experience

what are the two components of the skin (for developmental anatomy)

epidermis and dermis

what is the epidermis

outer protective layer of the skin covering dermis

the epidermis arises from the

ectoderm

the epidermis contains _______ which is made up of hair follicles and glands

adnexa

what is the dermis

a sensitive layer of skin below the epidermis

the dermis arises from

specialized somites called dermatomes

what is the presentation of collie eye anomaly (CEA)

blindness (most common)

various degrees of vision loss

collie eye anomaly is typically seen with other eye disorders like

microphthalmia and enophthalmia

what species will typically have collie eye anomaly

dogs

collies, shetland sheepdogs, aussies, border collies, novia scotia duck trolling retrievers

what is happening in collie eye anomaly

malformation of the retina, choroid, and sclera

what causes collie eye anomaly

optic cup was formed incorrectly

from autosomal genetic mutation

is collie eye anomaly always congenital

yes

what diagnostics are involved in collie eye anomaly

veterinary opthalmologist exam

is collie eye anomaly treatable

no

what is the prognosis for collie eye anomaly

conditions will not improve

if blind → stays blind

poor vision will never improve

what is the presentation for cataracts

vision loss, “cloudy” eyes

which species can have congenital cataracts

dogs, cats, rabbits, horses, cattle, sheep

what is happening when pets have congenital cataracts

opacities (white areas) of the lens or lens capsule

are cataracts congenital

no, can be acquired or age-related

what is the cause for cataracts

genetics

infections during pregnanciesw

what could cause congenital cataracts in humans

rubella or cytomegalovirus exposure during pregnancy

does genetic testing exist for congenital cataracts

yes - for certain dog breeds

what diagnostics are used for congenital cataracts

dilating pupil and examining lens

are congenital cataracts treatable

potentially - surgery to remove the lens and replace with artifical one

what is the prognosis for congenital cataracts

continued vision loss through life unless treated; not fatal