BL Flashcards
(212 cards)
1
Q
How do cells attach to the BM?
A
Hemidesmosomes OR focal adhesions (intracellular actin filaments connected to integrins which connect to the ECM)
2
Q
2 main functions of integrins
A
Attach the cell cytoskeleton to the ECM, signal transduction from the ECM to the cell
3
Q
Give examples of static, stable, and labile cells
A
Static/permanent: don’t regenerate, CNS, cardiac and skeletal myocytes
Stable: regenerate when necessary e.g. fibroblasts, endothelium, SM cells
Labile: constantly multiply with short lifespan e.g. blood, epithelium
4
Q
Differences between prokaryote and eukaryote
A
Pro: no nucleus, no mitochondria, cell wall
5
Q
Where are stereovilli found?
A
Middle ear hair cells and epididymis
6
Q
Where are cilia found?
A
Fallopian tube, bronchioles
7
Q
Name three fibres in CT and their functions
A
Collagen (high tensile strength and flexible), reticular (supporting framework), elastin (allows recoil)
8
Q
What is ground substance
A
Viscous, high water content, contains proteoglycans (which are core protein + GAGs)
9
Q
Name a glycosaminoglycan and what it does
A
Hyaluronic acid- attracts water, bound to proteoglycans, in the ground substance of cartilage, because of its swelling it resists compression
10
Q
What is a proteoglycan
A
core protein + GAGs attached
11
Q
Describe structure of types of CT proper (general CT)
A
Loose: sparse collagen, many cells, lots of ground substance, viscous
Dense: lots of collagen, few cells, not much ground substance
12
Q
What is the main role of loose CT and therefore where is it found
A
Good at transport/diffusion because lots of ground substance and viscous, so located beneath epithelium or around small blood vessels
13
Q
Describe the structure of types of dense CT
A
Regular has collagen in parallel bundles with fibroblasts in between to withstand stress in a single direction ie. tendons, ligaments, aponeuroses. Irregular has collagen in multiple directions with fibroblasts between for stress in multiple directions e.g. submucosa of intestine, deep layers of dermis.
14
Q
What is the structure of collagen in ligaments?
A
Densely packed in parallel bundles but undulate (like super noodles) and arranged in fascicles separated by loose CT
15
Q
What is an aponeurosis? and name one
A
Flat sheet of dense regular CT with bundles of fibres in one layer arranged 90 degrees to adjacent layers e.g. linea alba
16
Q
Name the layers of the abdominal wall in order
A
Skin, SC fat, external oblique, internal oblique, rectus abdominus, transversus abdominus
17
Q
What type of CT is the dermis?
A
Dense irregular (resists multiple stress directions)
18
Q
What do fibroblasts do?
A
Synthesis ground substance, procollagen, GAGs, glycoproteins
Important in wound healing and scar formation
Myofibroblasts contain actin and do wound contraction
19
Q
What types of collagen are there and where are they found
A
I- fibrils aggregate into fibres: skin, tendon, bone
II-fibrils do not form fibres (hyaline and elastic cartilage) cartilage
III-Fibrils form fibres around structures (reticulin)blood vs, LN capsule
IV- BM
20
Q
What is the structure of type I collagen?
A
Triple helix of a chains
21
Q
What do you need vitamin C for?
A
The intracellular production of procollagen by fibroblasts
22
Q
What is Marfan’s syndrome?
A
AD problem with fibrillin so elastic tissue is abnormal (abnormally tall, frequent joint dislocation, arachnodactyly, risk of aortic rupture)
23
Q
Where is elastin found?
A
Tunica media of aorta (produced by SM cells) and lungs
24
Q
Difference between white and brown adipose cells?
A
White contain one lipid droplet with nucleus pushed to the side, role in fuel reserve, thermal insulation, shock absorption.
Brown contain many lipid droplets and a central nucleus, especially found in newborn close to scapula, sternum, axillae, also present in upper chest and neck of adults, in thermogenesis
25
Why are brown fat cells brown?
Rich vascular supply and abundant mitochondria
26
Tell me about ghrelin and letpin
Ghrelin released from stomach and signals hunger, leptin released from adipose cells to tell you to stop eating
27
Explain the difference between CT, collagen, and cartilage
CT is loose or dense and a major group of body tissue types
Collagen is one fibre of CT (the others are reticular and elastin)
Cartilage is a type of CT that has type II collagen
28
Name components of the lymphatic system
MALT, GALT, tonsils. Peyer's patches (ileum), LNs, thymus, spleen
29
How does lymph move?
Deep lymphatics moved by adjacent muscles, abdo/thorax large lymphatics have SM in their walls
30
Where are follicular DCs?
In germinal centres, can cause B cell prolif
31
Functions of spleen
Destroys RBCs, antigen presentation, B and T cell activation, macrophages remove antigen from blood
32
What happens following splenectomy?
BM and liver can take over destroying RBCs, but increased risk of encapsulated (meningococcus) and malaria infection, increased risk of DVT and PE (maybe due to increased platelets?)
33
When can the spleen enlarge?
In response to systemic infection e.g. glandular fever, malaria, septicemia
34
When the thymus involute?
After puberty, by late teens is mostly fat
35
Where do neutrophils, mast cells, monocytes and basophils come from?
Myeloblast, which comes from a common myeloid progenitor
36
Where is McBurney's point?
Between umbilicus and ASIS, 2/3 from umbilicus
37
What occurs at the sternal angle?
T4/5 level, 2nd rib, aortic arch, tracheal bifurcation
38
What occurs at the level of the umbilicus
L3/4, bifurcation of aorta
39
Top of iliac crest is which level?
L4
40
Where is BM harvested from?
Iliac crest
41
Name layers of the gut mucosa
Epithelium, lamina propria, muscularis mucosae
42
What are serous membranes?
2 part membranes that line body cavities that don't open to exterior- peritoneum, pleural sacs, pericardial sac. Has epithelial layer and thin CT layer
43
What is mesothelium?
Simple squamous epithelium lining the pleural sac, pericardium and peritoneum
44
Name locations of simple squamous epithelium
Blood vessels (endothelium), pericardium/pleural sac/peritoneum (mesothelium), loop of henle, Bowman's capsule, pulmonary alveoli
45
Functions of simple squamous epithelium
Barrier (Bowman's capulse), lubrication (mesothelium), gas exchange (alveoli)
46
Where are simple cuboidal cells found?
Lines pancreatic duct, surround thyroid glands and synthesise thyroxine, CDs of kidney, surface of ovary
47
Functions of simple cuboidal cells?
Absorption and secretion in exocrine glands and kidney tubules, covering ovary, synthesis of thyroxine
48
Where are simple columnar cells found?
Fallopian tubes, colon
49
Where are simple columnar cells with microvilli found?
Jejunum
50
Function of simple columnar cells?
Absorption, secretion and lubrication in SI&LI, transport in fallopian tubes
51
Where is pseudostratified epithelium found?
URT (with cilia), nasal cavity, parotid gland, epididymis, vas deferens
52
What are functions of pseudostratified epithelium?
Mucus secretion and particle trapping and removal (URT),
53
Where are stratified squamous cells found?
Vagina, skin, oesophagus, oral cavity
54
Name layers of epidermis
Stratum corneum, granular layer, prickle cell layer, basal layer dermis
55
Why is the basal layer important in the epidermis?
Keratinocyte mitosis occurs here, then move upwards to the prickle layer where they terminally differentiate
56
What happens in the granular layer?
Keratinocytes lose their plasma membrane and become corneocytes
57
How long does it take for a keratinocyte to move upwards to the stratum corneum?
28-40 days
58
Name cells of the epidermis
Keratinocytes, corneocytes (in stratum corneum), Langerhans, melanocytes
59
What is transitional epithelium?
Stratified epi that can change shape from cuboidal/columnar to flat
60
Where is transitional epi found?
Ureter, bladder, urethra, renal calyces
61
Name a unicellular gland
Goblet cell!
62
What effects can CF have on GI?
Meconium ileus, constipation, poor absorption
63
What are merocrine, apocrine and holocrine secretion?
Merocrine is exocytosis, apocrine is droplets covered with plasma lemma e.g fat droplets in milk, holocrine is whole cell breakdown e.g. sebaceous gland of skin
64
Name some tubular glands
Intestinal crypts, gastric pits
65
What effects can CF have on pancreas?
Exocrine secretions are dehydrated, become thick and block the ducts, pancreatitis and fibrosis, poor absorption due to blocking enzymes
66
<5mm lump =
papule
67
5-10mm lump=
nodule
68
small water blister =
vesicle
69
larger water blister -
bulla
70
pus filled vesicle =
pustule
71
thread vein =
telangiectasia
72
non palpable area of discoloration =
macule
73
macule >2cm =
patch
74
palpable, flat topped area >2cm =
plaque
75
loss of epidermis
erosion
76
loss of epi and dermis
ulcer
77
What pathology is involved in psoriasis?
Rapidly proliferation in basal layer, desquamation of stratum corneum, leukocytes infiltrate
78
Thickening of the skin =
lichenification
79
Name the 3 types of cartilage
Hyaline, elastic, fibrocartilage
80
What is the only cell type found in healthy hyaline cartilage?
Chondrocytes
81
What cell type produces ECM in the cartilage?
Chondrocytes
82
Difference between collagen and cartilage?
Collagen is a type of fibre found in CT. Cartilage is a type of CT. Type II collagen is found in hyaline cartilage.
83
How do GAGs attract water?
They have lots of negative charges
84
Describe the structure of the three types of cartilage
Hyaline- type II collagen, GAGs, hyaluronic acid
Elastic- hyaline + elastin fibres
Fibrocartilage- hyaline + type I collagen
85
If chrondrocytes are recently divided, what are they called?
Isogenous groups
86
Role of hyaline cartilage in bones?
Precursor of bones for fetuses that develop by endochondrial ossification, some remains on long bones at the articulating surface and epiphyseal plate
87
What covers hyaline cartilage and what is its function?
Perichondrium which has cells that develop into chondroyctes
88
Explain appositional and interstitial growth
Appositional is chrondoblasts from the perichondrium secreting matrix
Interstitial is from chondrocytes dividing and producing isogenous groups that deposit matrix
89
Each chondrocyte lies in a...
Lacuna
90
What is NOT located at articulating surfaces and epiphyseal growth plates?
Perichondrium
91
Name regions of a bone
Epiphysis, metaphysis, diaphysis
92
What type of collagen is found in fibrocartilage?
Type I
93
What type of collagen is found in hyaline cartilage?
Type II
94
Where is elastic cartilage
Pinna, EAM, epiglottis, eustachian tube
95
What cell types are in fibrocartilage?
Chondrocytes and fibroblasts
96
Which types of cartilage have perichondrium?
Hyaline and elastic, NOT fibrocartilage
97
Where is fibrocartilage found?
IV discs, menisci of knee, pubic symphysis
98
Where is hyaline cartilage found?
Rib, nose, trachea, bronchi
99
How do long bones grow?
Hyaline is template for endochondral ossification which increases its length. Periosteal ossification increases the girth of the bone which is intramembraneous ossification. Cartilage is replaced by bone.
100
Describe the zones of epiphyseal growth
Cartilage to bone:
1. Zone of reserve cartilage (not actively becoming bone)
2. Zone of proliferation: chondrocytes multiply and arrange in columns
3. Zone of hypertrophy: chondrocytes stop dividing and just grow, walls of lacunae become thin.
4. Zone of calcification: between columns of the chondrocytes matrix is deposited and calcifies.
5. Zone of resorption: chondrocytes die as the lacuna walls breakdown, leaving columns between the calcified matrix that are invaded by blood vessels and osteoblasts/clasts. Clasts remove the temporary matrix laid down earlier and blasts deposit matrix in the bony spicule (become osteocytes if surrounded by matrix)
101
What happens in the zone of resorption?
chondrocytes die as the lacuna walls breakdown, leaving columns between the calcified matrix that are invaded by blood vessels and osteoblasts/clasts. Clasts remove the temporary matrix laid down earlier and blasts deposit matrix in the bony spicule (become osteocytes if surrounded by matrix)
102
What type of cartilage covers synovial joints?
Hyaline or fibrocartilage
103
How do flat bones and long bones develop?
Long bones by endochondral ossification and flat bones by intramembranous ossification
104
What is intramembranous ossification?
Flat bones develop like this and develop from mesenchymal tissue. Does not replace an existing template. e.g. skull, clavicle, scapula. Also thickens long bones at their periosteal surfaces (appositional growth)
105
What are the stages of intramembranous ossification
Mesenchymal stem cells (MSCs) form a nidus (a tight cluster). MSCs become osteoprogenitor cells (more Golgi and ER), become osteoblasts and lay down ECM containing type I collagen (osteoid). Osteoid mineralises to form spicules containing osteocytes surrounded by osteoblasts. Spicules join to form trabeculae, which merge to form woven bone, then replaced by mature compact bone
106
Spicule + spicule =
Trabeculae
107
What are the two types of bone?
Spongy/cancellous (spaces filled with BM) and compact bone on external surfaces of bone
108
What are Haversian and Volkmann's canals?
Haversian travels up an osteon (so at the centre of a ring), Volkmann's travels across an osteon
Carry blood vs, lymphatics and nerves
109
How is mature bone arranged?
Concentric lamellae of osteons
110
What are canaliculi (in bone)
Tiny canals which osteocytes project their cytoplasmic processes into to exchange nutrients between themselves
111
What structural differences are there between spongy and compact bone?
Compact bone has Haversian and Volkmann's canals, spongy doesn't. Spongy has BM in its gaps
112
What is a cutting cone?
Involved in bone remodelling, bores a tunnel through bone with osteoclasts, followed later by osteoblasts to lay down osteoid
113
Describe key components of bone
65% calcium hydroxypatite crystals, 23% type I collagen
114
Describe stages of fracture repair
1. Haematoma (blood vessels and periosteum break) and granulation tissue forms. Phagocytes and osteoclasts remove dead tissue, macrophages remove clot
2. Soft callus forms which is fibrocartilaginous tissue to splint the fracture, bony trabeculae develop as osteoblasts invade site. New blood vessels infiltrate
3. Hard callus of spongy bone forms from endochondral and intramembranous ossification (from 2 days-2months)
4. Spongy bone replaced by compact bone and bone remodelling occurs
115
Define osteoporosis
Enhanced bone resorption:formation, depletion of bone mass. Spongy bone is regularly remodelled but in osteoporosis the osteoclast resorption bays are not filled in again
116
What is primary osteoporosis?
Either type 1 or 2:
Type 1 in postmenopausal due to increased osteoclasts from decreased oestrogen
Type 2 is senile osteoporosis, >70yo due to reduced osteoblast function x
117
Risk factors for osteoporosis
Genetic (black bone mass higher than white or asian)
Insufficient calcium intake, insufficient calcium absorption via reduced vit D/decreased renal activation of vit D, immobilisation of bone, smoking
118
What colour skeletal muscle fibres exist and what's the difference
Red: small, very vascularised, slow weak contraction, fatigues slowly
Intermediate
White: large, poor vascularisation, few mitochondria, fast, strong contraction, fatigues quickly (e.g. finger muscles)
119
Where is myoglobin present?
Skeletal and cardiac muscle, NOT smooth
120
How does Hb relate to myoglobin?
Hb gives up oxygen to myoglobin, especially if low pH (as in active muscles from CO2/lactic acidosis)
121
What are epimysium, perimysium, and endomysium
Epimysium around a muscle, perimysium around a fascicle, endomysium around a muscle fibre
122
Describe the organisation of a sarcomere
Z discs at each end and H zone in the middle. Thick A band in the middle, think I bands either side
123
How often do muscles get remodelled?
Continually! Replaced in 2 weeks
124
Causes of atrophy
Disuse, with age (>30yo), denervation (LMN lesions)
125
How do muscles get longer?
Sarcomere addition
126
What's in a skeletal muscle?
Fasicles --> muscle fibre --> myofibrils --> myofilaments
127
What is the thin filament?
Actin with tropomyosin coiled around, and troponin complex attached to tropomyosin
128
Where is creatine kinase released from?
Skeletal muscle, brain, heart (can indicated IM injection, vigorous exercise, fall, rhabdomylolysis, muscular dystrophy, AKI
129
Describe myosin structure
Thick rod with two protruding heads. In the centre of the sarcomere it has no heads.
130
How does calcium cause muscle contraction?
Calcium binds to TnC of troponin, which causes a conformational change in tropomyosin and it moves away from blocking the actin binding site so that myosin head can bind actin
131
How does myosin head detach from actin?
As ATP attaches myosin detaches . Thats why in rigor mortis the myosin is still attached to actin.
132
What causes cocking of the myosin head?
Hydrolysis of ATP to ADP and Pi
133
Describe the process leading to contraction of skeletal muscle (start with nerve impulse)
Nerve impulse arrives at NMJ, Ach released into synaptic cleft, causes end plate potential of sarcolemma, voltage Na channels open, Na enters cell, depolarisation spread to T tubules, voltage sensors in T tubules trigger opening of Ca channels from terminal cisternae (of SR) into sarcoplasm, Ca binds to TnC
134
What's special about cardiac muscle?
Central nuclei, striated, intercalated disc, branching
135
What are intercalated discs for in cardiac muscle?
Have gap junctions for electrical coupling
136
What are ANP (from atria) and BNP (from ventricles) raised in?
HF
137
What are the actions of ANP/BNP?
Increase GFR for natriuresis and diuresis, vasodilation to reduce BP (counteract RAAS)
138
Describe structure of Purkinje fibres
Have glycogen +++, gap junctions +++, sparse myofilaments, rapid conduction
139
Describe structure of SM cells
Fusiform (spindle), no T tubules, no sarcomeres (but contraction still actin-myosin), slower contraction more sustained, less ATP needed. Actin and myosin arranged diagonally spiralling across so that it contracts in a twisting way!
140
Name two modified SM cells
Myoepithelial that surround exocrine glands (sweat, saliva, mammary) and in ciliary muscle
Myofibroblasts at wound healing to contract wound and tooth eruption
141
Which muscle cells can regenerate?
```
SM can (e.g. pregnant uterus)
Skeletal muscle cells can't but satellite cells (their progenitors) can. Satellite cells can also fuse with muscle cells to increase mass.
Cardiac muscle can't- fibroblasts divide and lay down scar tissue
```
142
Name end arteries and an absolute end artery
Coronary, splenic, cerebral, renal. Absolute end artery is central artery to the retina
143
Tunica media and tunica adventitia have which types of muscle fibres?
Media has circular muscle layers, adventitia has longitudinal
144
What is an arteriole?
Arteries with a diameter of <0.1mm, with 1-3 layers of muscle in tunica media only (arteries have x30)
145
What are arteries that supply blood to capillary beds called?
Metarterioles
146
What controls flow to capillary beds?
Precapillary sphincters of metarterioles
147
What vessels do capillaries lead to?
Post capillary venules
148
What are the only two cell types of a capillary and what do they do?
Single layer of endothelial + pericytes. Pericytes can divide into SM cells or fibroblasts in angiogenesis/healing
149
Veins vs arteries
Veins are larger diameter, higher capacitance, thinner wall with more CT and less elastic and muscle
150
Name the 4 layers of gut wall
Mucosa (epithelium, lamina propria, muscularis mucosae), submucosa, muscularis externae, serosa
151
Which layer are Peyer's patches often found?
Lamina propria of mucosa
152
Which layer of gut are glands, A&Vs, nerves found in?
Submucosa
153
What muscle types are found in muscularis externa?
Inner circular and outer longitudinal
154
What epithelium makes up the gut serosa
Simple squamous (mesothelium)
155
Name contents/function of saliva
IgA, amylase, lipase, lubricates food, high calcium for teeth,
156
Name the two innervation locations in the gut layers
Meissner's plexus in the submucosa, Auerbach's plexus between the two layers of the muscularis externa
157
Gastric glands are what types of glands?
Tubular
158
Gut glands are in the _____ layer, but gastric glands are in the ____
Submucosa, mucosa
159
What can damage mucous cells and what is their function?
Aspirin and alcohol can damage mucous cells. Mucus contains HCO3 to neutralise and is resistant to pepsin
160
Describe a gastric gland
Pit at top with mucous cells, then isthmus with stem cells and parietal cells, then neck, the base with chief cells, and G cells
161
What glands are in the duodenum?
Brunner's glands, which secrete HCO3
162
Give example of paracrine control in gut
Histamine controls acid production
163
What is the hepatic portal system?
Two capillary beds in series- one in stomach/gut and one in liver sinusoids
164
What converts ammonia (toxic and can cross BBB) to urea
Liver
165
What are lacteals and where do they lead?
Lymphatic vessels that drain into other lymphatics --> thoracic duct --> enters circulation between left jugular vein/left subclavian --> lipids enter liver through hepatic artery
166
What doesn't travel in the portal vein?
Lipids and ADEK vits
167
What does the liver produce?
Albumin, glycogen, IGF-1, thrombopoetin, angiotensinogen, activates vit D, bile
168
What blood vessels are connected to the liver
Hepatic artery (from coeliac trunk) and hepatic portal vein lead in, and hepatic vein leading to IVC drains
169
What's a sinusoid (in liver)
Mixing of arterial and venous blood from hepatic artery and hepatic portal vein
170
What's the space of disse?
Gaps between sinusoids and hepatocytes (dissed by the sinusoids and by the hepatocytes)
171
Where are Kupffer cells?
Lining the sinusoids
172
What are stellate/Ito cells
Store vit A in the liver, found in space of disse
173
Three signs of Horner's syndrome
Miosis, ptosis, and anhidrosis
174
How can lung cancer cause a hoarse voice?
Impingement on the left recurrent laryngeal nerve, supplies larynx muscles
OR if aortic aneurysm presses on LRLN
175
What are the conducting and respiratory airways?
Conducting is nasal cavity-terminal bronchioles, respiratory is respiratory bronchioles to alveoli
176
Name the sections air travels through to the lungs
Nasal cavity, pharynx, larynx, trachea, primary bronchi, secondary bronchi, bronchioles, terminal bronchioles, respiratory bronchioles, alveolar ducts, alveoli
177
Name epithelial types in the lungs
Nasal-secondary bronchi is pseudostratified with cilia and goblet cells
Bronchioles-terminal bronchioles is simple columnar with cilia and clara cells
Respiratory bronchioles-alveolar ducts is simple cuboidal with clara cells.
Alveoli is simple squamous
178
Which bronchus is more prone to having things fall down it?
Right bronchus because its more vertical
179
Tell me about cartilage in the lung
Trachea and primary bronchi have C shaped rings, secondary and tertiary bronchi have irregular islands
180
What blood vs supply and drain the lung?
Pulmonary VEIN SUPPLIES and pulmonary ARTERY drains
181
What do clara cells (terminal/respiratory bronchioles) secrete?
Surfactant lipoprotein to stop walls sticking together in expiration
182
What helps keeps the breasts up?
Cooper's suspensory ligaments
183
What type of glands are mammary?
Modified apocrine (part of cell lost in secretion) sweat glands
184
What is a lobule in the breast?
Many alveoli drained by a single lactiferous duct
185
The hypothalamus produces..
ADH and oxytocin, TRH
186
Give an example of neurocrine secretion
TRH released from hypothalamic neurons travels in blood to anterior pituitary to cause cells to release TSH
187
What are catecholamines, glucocorticoids and mineralocorticoids?
Gluco cortisol, mineral aldosterone, catecholamine adrenaline/NA
188
How is cortisol released?
Hypothalamus released CRH, ant pit releases ACTH, adrenal cortex releases cortisol (zona fasiculata)
189
Describe adrenal gland structure and what each layer makes
Cortex:
Zona glomerulosa- mineralocorticoid aldosterone
Zona fasiculata- glucocorticoid cortisol
Zona reticularis- androgens
Medulla - catecholamines adren/NA
190
What type of cells are in the adrenal medulla?
Chromaffin cells
191
What does the pineal gland produce?
Melatonin
192
Describe spermatogenesis
Diploid spermatogonium divides by mitosis --> 2 diploid primary spermatocytes --> meiosis 1 makes 2 haploid secondary spermatocytes --> meiosis II for 4 haploid spermatids
193
Describe oogenesis
Oogonium is diploid and divides by mitosis for 2 diploid (one primary oocyte and one oogonium), divides by meiosis I to form haploid oocyte and a polar body. Haploid oocyte ovulated and undergoes meiosis II if fertilised to produce haploid ovumx23 chromatids
194
Where does the oocyte pause
Primary oocyte pauses in prophase I of meiosis I
195
Where does fertilisation occur?
Ampulla of fallopian tube
196
How long are sperm and oocytes viable for?
Sperm 5 days, secondary oocyte 12-24hours
197
Difference between gestational age and embryonic age?
Gestational age = embryonic age (time since fertilisation) + 2 weeks
198
What is the germinal stage, embryonic period and fetal period
Germinal stage is fetilisation - 2 weeks, embryonic is 3-8weeks, foetal is 8-term
199
What is hatching?
Blastocyst breaking free of zona pellucida, which is needed to implant
200
What does the trophoblast become?
tropho=food, blast=bud, so food bud! Yolk sac and placenta
201
How is food for the embryo provided before and after 12th week
Pre 12th- histiotrophic (not from maternal blood)
| Post 12th- haemotrophic
202
What are normal implantation sites?
Superior and posterior wall (placenta previa if not)
203
What makes up the bilaminar disc
Hypoblast and epiblast (from embryoblast)
204
What happens in the week of 2s?
Trophoblast becomes the cytotrophoblast and syncytiotrophoblast, embryoblast becomes bilaminar (hypoblast and epiblast), hypoblast contributies to 2 cavities (yolk sac and chorionic cavity)
205
What feature appears on the epiblast in 3rd week?
Primitive streak and node. Marks the start of gastrulation
206
What is gastrulation?
Bilaminar disk becomes trilaminar disck (ecto, meso and endoderm). Epiblast cells migrate inwards (forming a pit)
207
How and when do we get left-right asymmetry
Before gastrulation the bilaminar disk is bilaterally symmetrical. After, ciliated cells at the primitive node result in left and right directed signalling molecules (sinus inversus can result from immotile cilia)
208
What is the notochord?
Midline cellular rod located cranially to the primitive streak that develops in week 3. Tells overlying ectoderm to become neuroectoderm and thicken to become the neural tube (neurulation)
209
What are somites?
Paraxial (by the neural tube) mesoderm segments, first pair appear at day 20 until week 5
210
What do somites form?
Dermatome, myotome and sclerotome (bones)
211
What does folding of the embryo do? (week 4)
Pulls amniotic membrane around so embryo is suspended, pulls connecting stalk ventrally, creates a ventral body wall, puts the heart in the right place
212
Name 3 MRI planes
Axial (cutting across transversely, coronal, sagittal
