biosci mod3 Flashcards
(142 cards)
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
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
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
4
Q
what is the epidermis mainly consisted of
A
layers of keratinocytes
5
Q
does the epidermis have structural strength
A
no, it does not have any structural strength
6
Q
What is the function of an epidermis
A
provides a barrier and continued renewal
7
Q
How does the epidermis get nutrients and remove waste?
A
all nutrient supply and waste removal of epidermis is through the dermis
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
9
Q
where are melanocytes found
A
they are classified as part of the epidermis
and they also reside at the basement membrane
10
Q
what is the function of melanocytes
A
pigmentation
reside at the basement membrane
and contacts keratinocytes
11
Q
Where are langerhan’s and merkel cells fo9und
A
they are found in the epidermis
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
13
Q
Why is stratification important for the epidermis
A
it is crucial for barrier function and continued renewal of the epidermis
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
15
Q
where is the stratum spinosum found
A
directly above the stratum basale
16
Q
how many layers are found in the stratum spinosum
A
it is 8-10 layers
17
Q
How are the cells held together in the stratum spinosum
A
keratin intermediate filaments and desmosomes hold cells together
18
Q
what is the appearance of keratinocytes in the stratum spinosum
A
they start to flatten out
19
Q
where is the stratum granulosum found
A
they are found directly under stratum lucidum
20
Q
what are the keratinocytes doing in the stratum granulosum
A
they are undergoing apoptosis
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
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
23
Q
Stratum lucidum are only present in
A
thick skin
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
25
Give an outline of the stratification process
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
26
stratification is a ....process
defined and controlled
27
in stratification, changes in gene expression are
very distinctive between epidermal layers
28
how often is a complete epidermal turnover
once a month
29
What is the dermis primarily made of
it is a dense matrix primarily made upof collagens and elastin fibres
30
Does the dermis have fibroblasts
yep
31
Does the thickness of the dermis vary in the body like epidermis
yes
32
how often is the turnover for the dermis
turnover is not very common-its minimal
| the dermis is quite stable
33
what cells are often found in the dermis
fibroblasts
immune cells
vasculature
nerve cells
34
what does the vasculature in the dermis do?
they help supply nutrients and remove waste for both dermis and epidermis
35
where are melanocytes found?
in the basement membrane
36
what do melanocytes do
they make melanoSOMEs-which contain the pigment melanin
| Melanosomes are transferred to keratinocytes
37
what is melanin
pigment that gives hair and skin its colour
38
what colour is pheomelanin
yellow/red
39
what colour is eumelanin
brown/black
40
what is the function of melanin
to protect from UV light
| what is a nuclear cap
41
what is a superficial wound
damage to the epidermis
42
what is a partial thickness wound
all of the epidermis
| and some of the dermis is destroyed
43
what is a full thickness wound
```
All of the epidermis and
dermis is destroyed
• Hypodermis can be destroyed
too, exposing bone and
muscle
```
44
why is a full thickness wound so hard to treat
Wound repair is very difficult
because all of the reservoirs of
epidermal stem cells have
been destroyed.
45
how is superficial wound healed
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
46
what is the process of partial thickness wound healing
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
47
how are full thickness wounds healed
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
48
what is the advantage of engineered skin
skin engineering could reduce the time to complete wound coverage
49
how does engineered skin work
```
Start with a small sample of
undamaged patient skin
• Isolate and expand skin cells
• Grow enough skin to cover all
wounds
```
50
before 8 weeks of human development, it is known as a...
after 8 weeks, it is known as a
first- embryo(what is zygote again?)
| then-foetus
51
what does embryogenesis achieve?
patterning
major axis defined
3 germ layers defined
rudiments of the major organs
52
what does patterning achieve? what exactly is it
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
53
what are the major axis defined in embryogenesis
anterior-near the head
posterior-near the tail
dorsal-at the back
ventral: tummy
54
What do the 3 germ layers tend to give rise to roughly?
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
55
what are the corona radiata and what do they do?
they are somatic cells that came with the egg when it was released. It portects the egg and releases hormones to attract semen
56
Zona pellucida
fibrous mat to bind to sperm; sperm has to burrow through
57
what is capacitation
takes off inhibitory molecules on the sperm and encourages them to swin harder and faster towards the egg
58
how is sperm directed towards the egg?
via thermostatic and chemotactic cues
59
when is meiosis completed in the egg
post fertilisation
60
why is the egg so 'uge
cuz it provides nutrients and everything the thing needs
61
is there still zona pellucida on the morula?
| why or why not?
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
how does the morula turn into the blastocyst
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
what are the 2 distinct cell types
trophoblast-gives rise to placenta
and
inner cell mass
64
why is it important to form a blastocyst cavity?
gives space for cells to move around
65
where does fertilisation take place?
in the fallopian tube
| about 24 hours post ovulation (check)
66
trophoblasts give rise to the
chorion-extraembryonic part of the embryo, which gives rise to the placenta
67
what is the function of trophoblasts
both release enzymes to burrow into the endometrial lining and prevents endometrium from shedding
68
the hypoblast forms the
endoderm
69
the epiblast forms the
ectoderm
70
before 8 weeks the babe is called
an embryo
71
after 8 weeks it is known as a
foetus
72
what does embryogenesis achieve
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
patterning
cells develop their identity where they are positioned
| and layering can be seen as the 3 germ layers
74
what does the ectodermal cells typically give rise to
tends to be closer to the outside,
| so skin, and nervous tissue-brain and spine
75
what does the meso cells typically give rise to
skeletal system, cardiovascular system, lymphatic, internal organs
76
what does the endo cells give rise to
gut and some glands
77
what are corona radiata
somatic cell that came with the egg when it was released from ovary, it protects and releases hormones to attract sperm
78
what is the zona pellucida
fibrous mat to bind to sperm
after this sperm has to burrow through
79
what is capacitation
takes off inhibiting molecules on the sperm and encourages the to swim harder and faster towards the egg
80
how is sperm directed towards the egg
thermostatic and chemostatic cues
81
what is the acrosome
a sac of enzymes that burrow through the layers
82
is meiosis completed in the egg during fertilisation
no, meiosis is completed in the egg after fertilisation
83
why is the egg so big?
egg has nutrients-everything made in egg initially
84
how does a morula become a blastocyst
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
why does the blastocyst need a cavity
give space in cells to move around
86
what does the trophoblast give rise to?
the placenta
87
what is the point of the zona pellucida?
to prevent ectopic pregnancies,
| with ectopic preganancies, we can't develop placenta
88
when does implantation take place
about 6 days after
89
what do trophoblasts do more specifically
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
what is the primitivie streak
it is visible streak that can be observed as cells of the epiblast migrate to form the endodrem or mesoderm
91
where is the trophoblast first seen?
it is first seen forming the outer shell of the morula
92
is the trophoblast replaced by the cells of the hypoblast?
no
93
the trophoblast forms the wall of the
blastocoel/ blastocyst cavity
94
what hormone does the trophoblast secrete
human chorionic gonadotrophin
95
the cellular trophoblast contributes to the formation of
the placenta
96
the cellular trophoblast contributes to the primary
chorionic villi
97
the syncitial trophoblast
contributes to the secondary chorionic villi
98
the syncitial trophoblast is in direct contact with
the mother's blood
99
what is the function of chorionic villi
chorionic villi are villi that sprout from the chorion to provide maximal contact area with maternal blood
100
what gives rise to the primary chorionic villi
the cellular trophoblast
101
what gives rise to the secondary chorionic villi
the syncytial trophoblast
102
how are neural crests formed?
(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
what do neural crest cells give rise to?
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
what is neurulation?
the process by which the neural plate, the neural folds and the neural tube being formed
105
what does the mesoderm form
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
what does the endoderm give rise to
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
what does the ectoderm give rise to
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
what kind of tissue are somites
mesoderm
109
what are the 3 kinds of regions in a somite
myotome
dermatome
sclerotome
110
what does each of the 3 regions of the somite develop into
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
When does the primitive streak form
about 15 days after fertilisation
112
the primitive steak defines
the midline and caudal end of the embryo
113
what is the epithelial=mesenchymal transformation
it is when epithelial cells become mesochymal cells which gives rise to meslderm
114
in gastrulation, whats the process of forming the mesoderm
epiblast cells goes into mesenchymal cells which transforms into mesoderm and endoderm
115
how is the endoderm formed
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
pharyngeal arches are formed by derivatives of
3 embryonic germ layers
117
the mesoderm of the pharyngeal arches will contribute to
the head/neck muscles and blood vvessels
118
the ectoderm of the pharyngeal arches will form
the epithelium of the mouth face and sensory ganglia of PNS
119
endodermof the pharyngeal arches will form
some glands and epithelium of the phrarynx
120
what does the cranial neural crest give rise to
the phrayngeal arches and the formation of skeleton (skull I'm guessing)and connective tissue
121
what happens between gastrulation and implantation
development of the trophoblast, bilaminar embryonic disc, development of the amnion and development of the yolk sac
122
the blastocyst cavity is lined with
before yolk sac formation; that would be the cellular trophoblast
after yolk sac formation:the hypoblast and exocoelemic membrane
123
what is the extracoelemic membrane
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
what gave rise to the amnion
the epiblast
125
the bilaminar disc is made up of
the hypoblast and the epiblast
126
what is the embryoblast
the thing that gives rise to the hypoblast and the epiblast, but most importantly, gives rise to the embryo directly
127
The cellular trophoblast gives rise to the
syncytial trophoblast
128
in comparison to the blastocyst, the yolk sac
cavity is rekatively empty and small
it decreases in size as development progresses
the blastocyst cavity is filled with fluid
129
what is the function of the yolk sac
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
what is the chorion made up of
extraembryonic mesoderm+trophoblast=chorion
| the cavity=extraembryonic coelom
131
what does the chorion give rise to
the placenta
132
what is the function of the chorion
protects the embryo and foetus from mother's immune response
133
how is the extraembryonic mesoderm formed
it is formed from cells migrating through the primitive streak.
it is after all, a bloody mesoderm
134
The extraembryonic mesoderm gives rise to the
umbilical cord, as it forms the connecting stalk.
| the connecting stalk gives rise to the umbilical cord
135
how does the primitive streak form
the primitive streak forms from the posterior to the anterior and forms along the midline
136
what are the 3 kinds of somites
myotome
sclerotome
dermatome
137
what gives rise to somites
paraxial mesoderm
138
what do each of the 3 kinds of somites give rise to?
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
The notochord has a role in
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
how is the notochord laid down
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
is the yolk sac an extraembryonic cavity?
yes
142
is the amniotic cavity an extraembryonic cavity?
yes
