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XIA BIOSCI107 > biosci mod3 > Flashcards

biosci mod3 Flashcards

1
Q

How does the human skin thermoregulate

A

thermoregulation

sweat glands- evaporation of sweat cools the body

blood vessels- vessel constriction in the dermis reduces blood flow= reduced heat loss, vasodilation in the dermis increases blood flow and = increased heat loss

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2
Q

What are the functions of human skin

A

blood reservoir- can hold 8 to 10% of the total blood volume

protection and barrier against
chemicals
pathogens
heat
UV
water loss

sensations
Vitamin D synthesis

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3
Q

what is the catch with Vitamin D synthesis in human skin

A

requires modification by UV before active form can be made in the liver

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4
Q

what is the epidermis mainly consisted of

A

layers of keratinocytes

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5
Q

does the epidermis have structural strength

A

no, it does not have any structural strength

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6
Q

What is the function of an epidermis

A

provides a barrier and continued renewal

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7
Q

How does the epidermis get nutrients and remove waste?

A

all nutrient supply and waste removal of epidermis is through the dermis

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8
Q

How many layers of epidermis does thick skin have

and how many layers of epidermis does thin skin have

A

thick skin has 5 layers, thin skin has 4 layers

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9
Q

where are melanocytes found

A

they are classified as part of the epidermis

and they also reside at the basement membrane

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10
Q

what is the function of melanocytes

A

pigmentation
reside at the basement membrane

and contacts keratinocytes

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11
Q

Where are langerhan’s and merkel cells fo9und

A

they are found in the epidermis

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12
Q

what is the function of langerhan’s cells

A

langerhan’s cells surveil the epidermis for foreign organisms

merkel celills extend into the bottom layer of the epidermis and detect touch sensations

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13
Q

Why is stratification important for the epidermis

A

it is crucial for barrier function and continued renewal of the epidermis

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14
Q

what is the stratum basale’s function

and what is it

A

it is the bottom layer of the epidermis

it is mostly made of the keratinocyte stem cells(check this fact)

the function is to transit amplifying keratinocytes

it has some melanocytes as well

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15
Q

where is the stratum spinosum found

A

directly above the stratum basale

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16
Q

how many layers are found in the stratum spinosum

A

it is 8-10 layers

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17
Q

How are the cells held together in the stratum spinosum

A

keratin intermediate filaments and desmosomes hold cells together

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18
Q

what is the appearance of keratinocytes in the stratum spinosum

A

they start to flatten out

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19
Q

where is the stratum granulosum found

A

they are found directly under stratum lucidum

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20
Q

what are the keratinocytes doing in the stratum granulosum

A

they are undergoing apoptosis

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21
Q

where are lamellar granules found and what do they do

A

fuse to plasma membrane and release lipid rich secretions to help form the barrier

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22
Q

where are the keratohyalin found

and what do they help form

A

they are dark granules and they help form keratin intermediate filaments into keratin

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23
Q

Stratum lucidum are only present in

A

thick skin

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24
Q

what is the stratum corneum made of and what do the keratinocytes look like

A

the keratinocytes overlap like scales of snake

the appearace is 25-30 layers of flattened dead keratinocytes

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25
Q

Give an outline of the stratification process

A

proliferating keratinocytes on the bottom of the epidermis push cells up and away from the dermis

Since all nutrients must come from the dermis, the further up the keratinocytes move up, they become less metabolicallly active and eventually they die, undergoing apoptosis

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26
Q

stratification is a ….process

A

defined and controlled

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27
Q

in stratification, changes in gene expression are

A

very distinctive between epidermal layers

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28
Q

how often is a complete epidermal turnover

A

once a month

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29
Q

What is the dermis primarily made of

A

it is a dense matrix primarily made upof collagens and elastin fibres

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30
Q

Does the dermis have fibroblasts

A

yep

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31
Q

Does the thickness of the dermis vary in the body like epidermis

A

yes

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32
Q

how often is the turnover for the dermis

A

turnover is not very common-its minimal

the dermis is quite stable

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33
Q

what cells are often found in the dermis

A

fibroblasts
immune cells
vasculature
nerve cells

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34
Q

what does the vasculature in the dermis do?

A

they help supply nutrients and remove waste for both dermis and epidermis

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35
Q

where are melanocytes found?

A

in the basement membrane

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36
Q

what do melanocytes do

A

they make melanoSOMEs-which contain the pigment melanin

Melanosomes are transferred to keratinocytes

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37
Q

what is melanin

A

pigment that gives hair and skin its colour

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38
Q

what colour is pheomelanin

A

yellow/red

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39
Q

what colour is eumelanin

A

brown/black

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40
Q

what is the function of melanin

A

to protect from UV light

what is a nuclear cap

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41
Q

what is a superficial wound

A

damage to the epidermis

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42
Q

what is a partial thickness wound

A

all of the epidermis

and some of the dermis is destroyed

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43
Q

what is a full thickness wound

A 
All of the epidermis and
dermis is destroyed
• Hypodermis can be destroyed
too, exposing bone and
muscle
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44
Q

why is a full thickness wound so hard to treat

A

Wound repair is very difficult
because all of the reservoirs of
epidermal stem cells have
been destroyed.

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45
Q

how is superficial wound healed

A

healing occurs by migration of keratinocytes from the wound edges and dermal appendages

once all the keratinocytes are in contact on all sides, the stratification can occur

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46
Q

what is the process of partial thickness wound healing

A

inflammatory phase-immune cells come in and clean the wound

2) migratory phase- keratinocytes migrate from the wound edge and appendanges to the clot-making collagen fibers
3) proliferative phase-keratinocytes proliferate
4) maturation phase- epidermal stratification and the scab falls off

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47
Q

how are full thickness wounds healed

A

split thickness skingraft

all of the epidermis
part of dermis removed, and then stapled on the skin

if over 30% of the body is burned, it requires multiple rounds of skin grafting

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48
Q

what is the advantage of engineered skin

A

skin engineering could reduce the time to complete wound coverage

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49
Q

how does engineered skin work

A 
Start with a small sample of
undamaged patient skin
• Isolate and expand skin cells
• Grow enough skin to cover all
wounds
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50
Q

before 8 weeks of human development, it is known as a…

after 8 weeks, it is known as a

A

first- embryo(what is zygote again?)

then-foetus

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51
Q

what does embryogenesis achieve?

A

patterning
major axis defined
3 germ layers defined
rudiments of the major organs

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52
Q

what does patterning achieve? what exactly is it

A

it is when cells develop their identity based on where they are (referred to in the slides as in time and space)

this includes the layering of the 3 germ layers

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53
Q

what are the major axis defined in embryogenesis

A

anterior-near the head
posterior-near the tail
dorsal-at the back
ventral: tummy

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54
Q

What do the 3 germ layers tend to give rise to roughly?

A

ectodermal-tend to be outside; includes brain, skin, spine, nervous tissue

meso-tend to be vessels- forms the (linings?check) of the skeletal system, cardiovascular system, lymphatic system. In summary, internal organs

Endoderm-tends to give rise to the gut and some glands

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55
Q

what are the corona radiata and what do they do?

A

they are somatic cells that came with the egg when it was released. It portects the egg and releases hormones to attract semen

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56
Q

Zona pellucida

A

fibrous mat to bind to sperm; sperm has to burrow through

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57
Q

what is capacitation

A

takes off inhibitory molecules on the sperm and encourages them to swin harder and faster towards the egg

58
Q

how is sperm directed towards the egg?

A

via thermostatic and chemotactic cues

59
Q

when is meiosis completed in the egg

A

post fertilisation

60
Q

why is the egg so ‘uge

A

cuz it provides nutrients and everything the thing needs

61
Q

is there still zona pellucida on the morula?

why or why not?

A

it lasts on the embryo until implantation-it tends to shed somewhere on the blastocyst

zona pellucida have the function of preventing ectopic pregnancies

62
Q

how does the morula turn into the blastocyst

A

the cells tend to huddle closer together and increases adhesion to each other. It eventially forms the first epithelial layer, where sodium pumps are activated and sodium pumped in encourages water to enter and form a blastocyst cavity

63
Q

what are the 2 distinct cell types

A

trophoblast-gives rise to placenta
and
inner cell mass

64
Q

why is it important to form a blastocyst cavity?

A

gives space for cells to move around

65
Q

where does fertilisation take place?

A

in the fallopian tube

about 24 hours post ovulation (check)

66
Q

trophoblasts give rise to the

A

chorion-extraembryonic part of the embryo, which gives rise to the placenta

67
Q

what is the function of trophoblasts

A

both release enzymes to burrow into the endometrial lining and prevents endometrium from shedding

68
Q

the hypoblast forms the

A

endoderm

69
Q

the epiblast forms the

A

ectoderm

70
Q

before 8 weeks the babe is called

A

an embryo

71
Q

after 8 weeks it is known as a

A

foetus

72
Q

what does embryogenesis achieve

A

1-patterning- cells acquire identity in space and time
2-the major axis are defined-anterior, posterior, dorsal, ventral
3- 3 germ layers are defined
4-rudiments of the major organs

73
Q

patterning

A

cells develop their identity where they are positioned

and layering can be seen as the 3 germ layers

74
Q

what does the ectodermal cells typically give rise to

A

tends to be closer to the outside,

so skin, and nervous tissue-brain and spine

75
Q

what does the meso cells typically give rise to

A

skeletal system, cardiovascular system, lymphatic, internal organs

76
Q

what does the endo cells give rise to

A

gut and some glands

77
Q

what are corona radiata

A

somatic cell that came with the egg when it was released from ovary, it protects and releases hormones to attract sperm

78
Q

what is the zona pellucida

A

fibrous mat to bind to sperm

after this sperm has to burrow through

79
Q

what is capacitation

A

takes off inhibiting molecules on the sperm and encourages the to swim harder and faster towards the egg

80
Q

how is sperm directed towards the egg

A

thermostatic and chemostatic cues

81
Q

what is the acrosome

A

a sac of enzymes that burrow through the layers

82
Q

is meiosis completed in the egg during fertilisation

A

no, meiosis is completed in the egg after fertilisation

83
Q

why is the egg so big?

A

egg has nutrients-everything made in egg initially

84
Q

how does a morula become a blastocyst

A

the cells of a morula huddle closer increase adhesion and forms the first epithelial layer

sodium pumps activated,
sodium pumps encourages water to pop in and once water is in, it forms a cavity

85
Q

why does the blastocyst need a cavity

A

give space in cells to move around

86
Q

what does the trophoblast give rise to?

A

the placenta

87
Q

what is the point of the zona pellucida?

A

to prevent ectopic pregnancies,

with ectopic preganancies, we can’t develop placenta

88
Q

when does implantation take place

A

about 6 days after

89
Q

what do trophoblasts do more specifically

A

both release enzymes that burrow into human chorionic gonadotrophin: which prevents endometrium from shedding

it also gives rise to the chroion the extraembryonic part of the embryo

90
Q

what is the primitivie streak

A

it is visible streak that can be observed as cells of the epiblast migrate to form the endodrem or mesoderm

91
Q

where is the trophoblast first seen?

A

it is first seen forming the outer shell of the morula

92
Q

is the trophoblast replaced by the cells of the hypoblast?

A

no

93
Q

the trophoblast forms the wall of the

A

blastocoel/ blastocyst cavity

94
Q

what hormone does the trophoblast secrete

A

human chorionic gonadotrophin

95
Q

the cellular trophoblast contributes to the formation of

A

the placenta

96
Q

the cellular trophoblast contributes to the primary

A

chorionic villi

97
Q

the syncitial trophoblast

A

contributes to the secondary chorionic villi

98
Q

the syncitial trophoblast is in direct contact with

A

the mother’s blood

99
Q

what is the function of chorionic villi

A

chorionic villi are villi that sprout from the chorion to provide maximal contact area with maternal blood

100
Q

what gives rise to the primary chorionic villi

A

the cellular trophoblast

101
Q

what gives rise to the secondary chorionic villi

A

the syncytial trophoblast

102
Q

how are neural crests formed?

A

(according to Chen) the neural fold joins to form the neural tube, a few layers of the ectodermal cells cells from the neural tube forms the neural crest, they tend to migrate migrate away from the neural tube.

103
Q

what do neural crest cells give rise to?

A

peripheral nerves, (all sensory of neurons and postganglionic neurons of the postganglionic neurons) at least.

The adrenal medullae

the pigment cells of the skin

some parts of the brain and spinal chord

almost all skeletal and connective tissue components of the head

104
Q

what is neurulation?

A

the process by which the neural plate, the neural folds and the neural tube being formed

105
Q

what does the mesoderm form

A

all skeletal and cardiac muscle tissue and most of smooth muscle tissue

cartilage, bone and other connective tissues

blood vessels, lymphatic vessels

dermis

mesothelium of thoracic, abdominal and pelvic cavities

kidneys and ureters, adrenal cortex
gonads

“dura mater”

106
Q

what does the endoderm give rise to

A

the epithelial lining of the gastrointestinal tract, except for the anal and oral cavities)
epithelium of glands

epithelial lining of urinary bladder, gall bladder and liver

epithelial lining of pharynx, auditory tubes, tonsils, typanic cavity, larynx, trachea

forms gametes-sperm and oocytes

epithelium of thyroid gland, parathyroid glands, pancreas and thymus

epithelial lining of prostate, prostate glands, vaginal parts

107
Q

what does the ectoderm give rise to

A

all nervous tissue
epidermis of skin
hair follicles, arrector pili muscles, nails, epithelium of skin glands and mammary glands

lens, cornea, internal eye muscles

internal and external ear

neuroepithelium of sense organs

epithelium of oral, nasal anal cavity

melanocytes

skeletal and connective tissue of head

arachnoid mater and pia mater

108
Q

what kind of tissue are somites

A

mesoderm

109
Q

what are the 3 kinds of regions in a somite

A

myotome
dermatome
sclerotome

110
Q

what does each of the 3 regions of the somite develop into

A

myotome develops into skeletal muscles of the neck, trunk and limbs

dermatome forms connective tissue

including the dermis of skin

sclerotomes give rise to vertebrae and reibs

111
Q

When does the primitive streak form

A

about 15 days after fertilisation

112
Q

the primitive steak defines

A

the midline and caudal end of the embryo

113
Q

what is the epithelial=mesenchymal transformation

A

it is when epithelial cells become mesochymal cells which gives rise to meslderm

114
Q

in gastrulation, whats the process of forming the mesoderm

A

epiblast cells goes into mesenchymal cells which transforms into mesoderm and endoderm

115
Q

how is the endoderm formed

A

it is first formed as a wave of migratory cells during gastrulation to form a flat sheet tha occupies the roof of the yolksac

116
Q

pharyngeal arches are formed by derivatives of

A

3 embryonic germ layers

117
Q

the mesoderm of the pharyngeal arches will contribute to

A

the head/neck muscles and blood vvessels

118
Q

the ectoderm of the pharyngeal arches will form

A

the epithelium of the mouth face and sensory ganglia of PNS

119
Q

endodermof the pharyngeal arches will form

A

some glands and epithelium of the phrarynx

120
Q

what does the cranial neural crest give rise to

A

the phrayngeal arches and the formation of skeleton (skull I’m guessing)and connective tissue

121
Q

what happens between gastrulation and implantation

A

development of the trophoblast, bilaminar embryonic disc, development of the amnion and development of the yolk sac

122
Q

the blastocyst cavity is lined with

A

before yolk sac formation; that would be the cellular trophoblast

after yolk sac formation:the hypoblast and exocoelemic membrane

123
Q

what is the extracoelemic membrane

A

they are cells at the edge of the hypoblast that migrate and cover the inner surface of the blastocyst wall

i.e, the yolk sac=exocoelemic membrane+hypoblast

124
Q

what gave rise to the amnion

A

the epiblast

125
Q

the bilaminar disc is made up of

A

the hypoblast and the epiblast

126
Q

what is the embryoblast

A

the thing that gives rise to the hypoblast and the epiblast, but most importantly, gives rise to the embryo directly

127
Q

The cellular trophoblast gives rise to the

A

syncytial trophoblast

128
Q

in comparison to the blastocyst, the yolk sac

A

cavity is rekatively empty and small
it decreases in size as development progresses

the blastocyst cavity is filled with fluid

129
Q

what is the function of the yolk sac

A

it supplies nutrients to the embryo during the 2nd and 3rd week of development and is the source of blood cells from the third to 6th week of development

presumably the yolk sac contributes to the formation of blood vessels of the chorion

130
Q

what is the chorion made up of

A

extraembryonic mesoderm+trophoblast=chorion

the cavity=extraembryonic coelom

131
Q

what does the chorion give rise to

A

the placenta

132
Q

what is the function of the chorion

A

protects the embryo and foetus from mother’s immune response

133
Q

how is the extraembryonic mesoderm formed

A

it is formed from cells migrating through the primitive streak.
it is after all, a bloody mesoderm

134
Q

The extraembryonic mesoderm gives rise to the

A

umbilical cord, as it forms the connecting stalk.

the connecting stalk gives rise to the umbilical cord

135
Q

how does the primitive streak form

A

the primitive streak forms from the posterior to the anterior and forms along the midline

136
Q

what are the 3 kinds of somites

A

myotome
sclerotome
dermatome

137
Q

what gives rise to somites

A

paraxial mesoderm

138
Q

what do each of the 3 kinds of somites give rise to?

A

myotome forms skeletal muscles of the neck, trunk and limbs
the dermatome give rise to the connective tissue, including the dermis of the skin

the scelrotome gives rise to the vertebrae and ribs

139
Q

The notochord has a role in

A

instructing cells in what they are supposed to develop into( this is called induction)
e.g-it induces the formation of the neural plate

140
Q

how is the notochord laid down

A

quite similar to the primitive streak, it lays down in the midline during gastrulation,
mesodermal cells from the primitive node migrate toward the head end of the embryo and form a hollow tube of cells in the midline called the notochordal process, the notochordal process becomes a solid cylinder of cells called the notochord

141
Q

is the yolk sac an extraembryonic cavity?

A

yes

142
Q

is the amniotic cavity an extraembryonic cavity?

A

yes

XIA BIOSCI107 (5 decks)

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