BL Flashcards
How do cells attach to the BM?
Hemidesmosomes OR focal adhesions (intracellular actin filaments connected to integrins which connect to the ECM)
2 main functions of integrins
Attach the cell cytoskeleton to the ECM, signal transduction from the ECM to the cell
Give examples of static, stable, and labile cells
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
Differences between prokaryote and eukaryote
Pro: no nucleus, no mitochondria, cell wall
Where are stereovilli found?
Middle ear hair cells and epididymis
Where are cilia found?
Fallopian tube, bronchioles
Name three fibres in CT and their functions
Collagen (high tensile strength and flexible), reticular (supporting framework), elastin (allows recoil)
What is ground substance
Viscous, high water content, contains proteoglycans (which are core protein + GAGs)
Name a glycosaminoglycan and what it does
Hyaluronic acid- attracts water, bound to proteoglycans, in the ground substance of cartilage, because of its swelling it resists compression
What is a proteoglycan
core protein + GAGs attached
Describe structure of types of CT proper (general CT)
Loose: sparse collagen, many cells, lots of ground substance, viscous
Dense: lots of collagen, few cells, not much ground substance
What is the main role of loose CT and therefore where is it found
Good at transport/diffusion because lots of ground substance and viscous, so located beneath epithelium or around small blood vessels
Describe the structure of types of dense CT
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.
What is the structure of collagen in ligaments?
Densely packed in parallel bundles but undulate (like super noodles) and arranged in fascicles separated by loose CT
What is an aponeurosis? and name one
Flat sheet of dense regular CT with bundles of fibres in one layer arranged 90 degrees to adjacent layers e.g. linea alba
Name the layers of the abdominal wall in order
Skin, SC fat, external oblique, internal oblique, rectus abdominus, transversus abdominus
What type of CT is the dermis?
Dense irregular (resists multiple stress directions)
What do fibroblasts do?
Synthesis ground substance, procollagen, GAGs, glycoproteins
Important in wound healing and scar formation
Myofibroblasts contain actin and do wound contraction
What types of collagen are there and where are they found
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
What is the structure of type I collagen?
Triple helix of a chains
What do you need vitamin C for?
The intracellular production of procollagen by fibroblasts
What is Marfan’s syndrome?
AD problem with fibrillin so elastic tissue is abnormal (abnormally tall, frequent joint dislocation, arachnodactyly, risk of aortic rupture)
Where is elastin found?
Tunica media of aorta (produced by SM cells) and lungs
Difference between white and brown adipose cells?
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
Why are brown fat cells brown?
Rich vascular supply and abundant mitochondria
Tell me about ghrelin and letpin
Ghrelin released from stomach and signals hunger, leptin released from adipose cells to tell you to stop eating
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
Name components of the lymphatic system
MALT, GALT, tonsils. Peyer’s patches (ileum), LNs, thymus, spleen
How does lymph move?
Deep lymphatics moved by adjacent muscles, abdo/thorax large lymphatics have SM in their walls
Where are follicular DCs?
In germinal centres, can cause B cell prolif
Functions of spleen
Destroys RBCs, antigen presentation, B and T cell activation, macrophages remove antigen from blood
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?)
When can the spleen enlarge?
In response to systemic infection e.g. glandular fever, malaria, septicemia
When the thymus involute?
After puberty, by late teens is mostly fat
Where do neutrophils, mast cells, monocytes and basophils come from?
Myeloblast, which comes from a common myeloid progenitor
Where is McBurney’s point?
Between umbilicus and ASIS, 2/3 from umbilicus
What occurs at the sternal angle?
T4/5 level, 2nd rib, aortic arch, tracheal bifurcation
What occurs at the level of the umbilicus
L3/4, bifurcation of aorta
Top of iliac crest is which level?
L4
Where is BM harvested from?
Iliac crest
Name layers of the gut mucosa
Epithelium, lamina propria, muscularis mucosae
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
What is mesothelium?
Simple squamous epithelium lining the pleural sac, pericardium and peritoneum
Name locations of simple squamous epithelium
Blood vessels (endothelium), pericardium/pleural sac/peritoneum (mesothelium), loop of henle, Bowman’s capsule, pulmonary alveoli
Functions of simple squamous epithelium
Barrier (Bowman’s capulse), lubrication (mesothelium), gas exchange (alveoli)
Where are simple cuboidal cells found?
Lines pancreatic duct, surround thyroid glands and synthesise thyroxine, CDs of kidney, surface of ovary
Functions of simple cuboidal cells?
Absorption and secretion in exocrine glands and kidney tubules, covering ovary, synthesis of thyroxine
Where are simple columnar cells found?
Fallopian tubes, colon
Where are simple columnar cells with microvilli found?
Jejunum
Function of simple columnar cells?
Absorption, secretion and lubrication in SI&LI, transport in fallopian tubes
Where is pseudostratified epithelium found?
URT (with cilia), nasal cavity, parotid gland, epididymis, vas deferens
What are functions of pseudostratified epithelium?
Mucus secretion and particle trapping and removal (URT),
Where are stratified squamous cells found?
Vagina, skin, oesophagus, oral cavity
Name layers of epidermis
Stratum corneum, granular layer, prickle cell layer, basal layer dermis
Why is the basal layer important in the epidermis?
Keratinocyte mitosis occurs here, then move upwards to the prickle layer where they terminally differentiate
What happens in the granular layer?
Keratinocytes lose their plasma membrane and become corneocytes
How long does it take for a keratinocyte to move upwards to the stratum corneum?
28-40 days
Name cells of the epidermis
Keratinocytes, corneocytes (in stratum corneum), Langerhans, melanocytes
What is transitional epithelium?
Stratified epi that can change shape from cuboidal/columnar to flat
Where is transitional epi found?
Ureter, bladder, urethra, renal calyces
Name a unicellular gland
Goblet cell!
What effects can CF have on GI?
Meconium ileus, constipation, poor absorption
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
Name some tubular glands
Intestinal crypts, gastric pits
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
<5mm lump =
papule
5-10mm lump=
nodule
small water blister =
vesicle
larger water blister -
bulla
pus filled vesicle =
pustule
thread vein =
telangiectasia
non palpable area of discoloration =
macule
macule >2cm =
patch
palpable, flat topped area >2cm =
plaque
loss of epidermis
erosion
loss of epi and dermis
ulcer
What pathology is involved in psoriasis?
Rapidly proliferation in basal layer, desquamation of stratum corneum, leukocytes infiltrate
Thickening of the skin =
lichenification
Name the 3 types of cartilage
Hyaline, elastic, fibrocartilage
What is the only cell type found in healthy hyaline cartilage?
Chondrocytes
What cell type produces ECM in the cartilage?
Chondrocytes
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.
How do GAGs attract water?
They have lots of negative charges
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
If chrondrocytes are recently divided, what are they called?
Isogenous groups
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
What covers hyaline cartilage and what is its function?
Perichondrium which has cells that develop into chondroyctes
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
Each chondrocyte lies in a…
Lacuna
What is NOT located at articulating surfaces and epiphyseal growth plates?
Perichondrium
Name regions of a bone
Epiphysis, metaphysis, diaphysis
What type of collagen is found in fibrocartilage?
Type I
What type of collagen is found in hyaline cartilage?
Type II
Where is elastic cartilage
Pinna, EAM, epiglottis, eustachian tube
What cell types are in fibrocartilage?
Chondrocytes and fibroblasts
Which types of cartilage have perichondrium?
Hyaline and elastic, NOT fibrocartilage
Where is fibrocartilage found?
IV discs, menisci of knee, pubic symphysis
Where is hyaline cartilage found?
Rib, nose, trachea, bronchi
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.
Describe the zones of epiphyseal growth
Cartilage to bone:
- Zone of reserve cartilage (not actively becoming bone)
- Zone of proliferation: chondrocytes multiply and arrange in columns
- Zone of hypertrophy: chondrocytes stop dividing and just grow, walls of lacunae become thin.
- Zone of calcification: between columns of the chondrocytes matrix is deposited and calcifies.
- 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)
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)
What type of cartilage covers synovial joints?
Hyaline or fibrocartilage
How do flat bones and long bones develop?
Long bones by endochondral ossification and flat bones by intramembranous ossification
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)
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
Spicule + spicule =
Trabeculae
What are the two types of bone?
Spongy/cancellous (spaces filled with BM) and compact bone on external surfaces of bone
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
How is mature bone arranged?
Concentric lamellae of osteons
What are canaliculi (in bone)
Tiny canals which osteocytes project their cytoplasmic processes into to exchange nutrients between themselves
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
What is a cutting cone?
Involved in bone remodelling, bores a tunnel through bone with osteoclasts, followed later by osteoblasts to lay down osteoid
Describe key components of bone
65% calcium hydroxypatite crystals, 23% type I collagen
Describe stages of fracture repair
- Haematoma (blood vessels and periosteum break) and granulation tissue forms. Phagocytes and osteoclasts remove dead tissue, macrophages remove clot
- Soft callus forms which is fibrocartilaginous tissue to splint the fracture, bony trabeculae develop as osteoblasts invade site. New blood vessels infiltrate
- Hard callus of spongy bone forms from endochondral and intramembranous ossification (from 2 days-2months)
- Spongy bone replaced by compact bone and bone remodelling occurs
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
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
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
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)
Where is myoglobin present?
Skeletal and cardiac muscle, NOT smooth
How does Hb relate to myoglobin?
Hb gives up oxygen to myoglobin, especially if low pH (as in active muscles from CO2/lactic acidosis)
What are epimysium, perimysium, and endomysium
Epimysium around a muscle, perimysium around a fascicle, endomysium around a muscle fibre
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
How often do muscles get remodelled?
Continually! Replaced in 2 weeks
Causes of atrophy
Disuse, with age (>30yo), denervation (LMN lesions)
How do muscles get longer?
Sarcomere addition
What’s in a skeletal muscle?
Fasicles –> muscle fibre –> myofibrils –> myofilaments
What is the thin filament?
Actin with tropomyosin coiled around, and troponin complex attached to tropomyosin
Where is creatine kinase released from?
Skeletal muscle, brain, heart (can indicated IM injection, vigorous exercise, fall, rhabdomylolysis, muscular dystrophy, AKI
Describe myosin structure
Thick rod with two protruding heads. In the centre of the sarcomere it has no heads.
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
How does myosin head detach from actin?
As ATP attaches myosin detaches . Thats why in rigor mortis the myosin is still attached to actin.
What causes cocking of the myosin head?
Hydrolysis of ATP to ADP and Pi
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
What’s special about cardiac muscle?
Central nuclei, striated, intercalated disc, branching
What are intercalated discs for in cardiac muscle?
Have gap junctions for electrical coupling
What are ANP (from atria) and BNP (from ventricles) raised in?
HF
What are the actions of ANP/BNP?
Increase GFR for natriuresis and diuresis, vasodilation to reduce BP (counteract RAAS)
Describe structure of Purkinje fibres
Have glycogen +++, gap junctions +++, sparse myofilaments, rapid conduction
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!
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
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
Name end arteries and an absolute end artery
Coronary, splenic, cerebral, renal. Absolute end artery is central artery to the retina
Tunica media and tunica adventitia have which types of muscle fibres?
Media has circular muscle layers, adventitia has longitudinal
What is an arteriole?
Arteries with a diameter of <0.1mm, with 1-3 layers of muscle in tunica media only (arteries have x30)
What are arteries that supply blood to capillary beds called?
Metarterioles
What controls flow to capillary beds?
Precapillary sphincters of metarterioles
What vessels do capillaries lead to?
Post capillary venules
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
Veins vs arteries
Veins are larger diameter, higher capacitance, thinner wall with more CT and less elastic and muscle
Name the 4 layers of gut wall
Mucosa (epithelium, lamina propria, muscularis mucosae), submucosa, muscularis externae, serosa
Which layer are Peyer’s patches often found?
Lamina propria of mucosa
Which layer of gut are glands, A&Vs, nerves found in?
Submucosa
What muscle types are found in muscularis externa?
Inner circular and outer longitudinal
What epithelium makes up the gut serosa
Simple squamous (mesothelium)
Name contents/function of saliva
IgA, amylase, lipase, lubricates food, high calcium for teeth,
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
Gastric glands are what types of glands?
Tubular
Gut glands are in the _____ layer, but gastric glands are in the ____
Submucosa, mucosa
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
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
What glands are in the duodenum?
Brunner’s glands, which secrete HCO3
Give example of paracrine control in gut
Histamine controls acid production
What is the hepatic portal system?
Two capillary beds in series- one in stomach/gut and one in liver sinusoids
What converts ammonia (toxic and can cross BBB) to urea
Liver
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
What doesn’t travel in the portal vein?
Lipids and ADEK vits
What does the liver produce?
Albumin, glycogen, IGF-1, thrombopoetin, angiotensinogen, activates vit D, bile
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
What’s a sinusoid (in liver)
Mixing of arterial and venous blood from hepatic artery and hepatic portal vein
What’s the space of disse?
Gaps between sinusoids and hepatocytes (dissed by the sinusoids and by the hepatocytes)
Where are Kupffer cells?
Lining the sinusoids
What are stellate/Ito cells
Store vit A in the liver, found in space of disse
Three signs of Horner’s syndrome
Miosis, ptosis, and anhidrosis
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
What are the conducting and respiratory airways?
Conducting is nasal cavity-terminal bronchioles, respiratory is respiratory bronchioles to alveoli
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
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
Which bronchus is more prone to having things fall down it?
Right bronchus because its more vertical
Tell me about cartilage in the lung
Trachea and primary bronchi have C shaped rings, secondary and tertiary bronchi have irregular islands
What blood vs supply and drain the lung?
Pulmonary VEIN SUPPLIES and pulmonary ARTERY drains
What do clara cells (terminal/respiratory bronchioles) secrete?
Surfactant lipoprotein to stop walls sticking together in expiration
What helps keeps the breasts up?
Cooper’s suspensory ligaments
What type of glands are mammary?
Modified apocrine (part of cell lost in secretion) sweat glands
What is a lobule in the breast?
Many alveoli drained by a single lactiferous duct
The hypothalamus produces..
ADH and oxytocin, TRH
Give an example of neurocrine secretion
TRH released from hypothalamic neurons travels in blood to anterior pituitary to cause cells to release TSH
What are catecholamines, glucocorticoids and mineralocorticoids?
Gluco cortisol, mineral aldosterone, catecholamine adrenaline/NA
How is cortisol released?
Hypothalamus released CRH, ant pit releases ACTH, adrenal cortex releases cortisol (zona fasiculata)
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
What type of cells are in the adrenal medulla?
Chromaffin cells
What does the pineal gland produce?
Melatonin
Describe spermatogenesis
Diploid spermatogonium divides by mitosis –> 2 diploid primary spermatocytes –> meiosis 1 makes 2 haploid secondary spermatocytes –> meiosis II for 4 haploid spermatids
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
Where does the oocyte pause
Primary oocyte pauses in prophase I of meiosis I
Where does fertilisation occur?
Ampulla of fallopian tube
How long are sperm and oocytes viable for?
Sperm 5 days, secondary oocyte 12-24hours
Difference between gestational age and embryonic age?
Gestational age = embryonic age (time since fertilisation) + 2 weeks
What is the germinal stage, embryonic period and fetal period
Germinal stage is fetilisation - 2 weeks, embryonic is 3-8weeks, foetal is 8-term
What is hatching?
Blastocyst breaking free of zona pellucida, which is needed to implant
What does the trophoblast become?
tropho=food, blast=bud, so food bud! Yolk sac and placenta
How is food for the embryo provided before and after 12th week
Pre 12th- histiotrophic (not from maternal blood)
Post 12th- haemotrophic
What are normal implantation sites?
Superior and posterior wall (placenta previa if not)
What makes up the bilaminar disc
Hypoblast and epiblast (from embryoblast)
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)
What feature appears on the epiblast in 3rd week?
Primitive streak and node. Marks the start of gastrulation
What is gastrulation?
Bilaminar disk becomes trilaminar disck (ecto, meso and endoderm). Epiblast cells migrate inwards (forming a pit)
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)
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)
What are somites?
Paraxial (by the neural tube) mesoderm segments, first pair appear at day 20 until week 5
What do somites form?
Dermatome, myotome and sclerotome (bones)
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
Name 3 MRI planes
Axial (cutting across transversely, coronal, sagittal
