ToB Sessions 1-6 Flashcards
1
Q
What are stereocillia, found in the lumen of vas deferens?
A
Non-motile microvilli modified for absorption
2
Q
What cell adaptation is found on cells in the trachea, bronchi and larger bronchioles?
A
Motile cilia
3
Q
What type of epithelia lines small excretory ducts?
A
Simple cuboidal
4
Q
What lines the apical surfaces in the proximal convoluted tubule?
A
Microvilli brush border
5
Q
Which type of organs is simple columnar epithelium seen in?
A
Digestive
6
Q
What does simple columnar epithelium exhibit in the small intestine?
A
Microvilli
7
Q
What is the function of simple squamous epithelium?
A
Reduce friction by producing lubricating fluids
8
Q
What is mesothelium?
A
Simple squamous tissue found on the external surfaces of digestive organs, lungs and heart
9
Q
What type of transport occurs across simple squamous tissue?
A
Passive
10
Q
Which passive transport surfaces are formed by simple squamous epithelium?
A
Pleural, pericardial and peritoneal cavities
11
Q
What is endothelium?
A
Simple squamous tissue in the lumina of heart chambers, blood vessels and lymphatic vessels
12
Q
What epithelium is found on larger excretory ducts of pancreas, salivary glands and sweat glands?
A
Stratified columnar and cuboidal
13
Q
How do basal stratified squamous cells transition from being cuboidal in shape to being truly squamous shaped?
A
Migrate and squash
14
Q
Where is non-keratinised stratified squamous epithelium found?
A
On moist cavities e.g. mouth, pharynx, eosophagus, vagina
15
Q
Where is keratinised stratified squamous epithelium found?
A
Stratum corneu my
16
Q
How does the connective tissue in stratified squamous tissue vary I the cornea?
A
Smooth when typically it is wavy
17
Q
What is the function of stratified squamous epithelium?
A
Withstand wear and tear
18
Q
Where is stratified transitional epithelium found?
A
Urinary system
19
Q
What does stratified transitional epithelium resemble when stretched?
A
Stratified squamous epithelium
20
Q
What is visible in superficial cells of stratified transitional epithelium?
A
Binucleate cells
21
Q
What is the function of stratified transitional epithelium?
A
Osmotic barrier to tissue fluids
22
Q
What are cells in epithelium joined by?
A
Lateral contacts
23
Q
What are tight junctions?
A
Where klaus a proteins fuse between cells
24
Q
Where are demosomes used?
A
Epithelia under large mechanical stress
25
How do demosomes join epithelial cells?
Interlock like a zip providing constant tension
26
What forms the basement membrane?
Reticular lamina
Basal lamina
Lamina propria
27
What is the function of the basement membrane?
Selectively filter
| Scaffold
28
What are the non-cellular components of epithelium that can be seen by light microscope?
```
Glycoproteins
Collagen fibres
Lymphocytes
Macrophages
Fibroblasts
```
29
What secretes glycoproteins in epithelium?
Epithelial cells
30
What is the blood supply to the epithelium like?
Avascular, supplied by diffusion
31
Is epithelium innervated?
Yep
32
How do simple and stratified epithelium differ?
```
Simple = single layer
Stratified = numerous cell layers
```
33
How many cell layers are there in pseudostritified epithelium?
One
34
What gives pseudostritified epithelium its apparently stratified appearance?
Different heights of cells
35
What are glands?
Aggregates of epithelial cells which perform specific secretory functions
36
What is an endocrine gland?
Releases secretory products in pro vascular or lymphatic system
37
How are endocrine glands arranged?
Cords, follicles or clusters around profuse blood supply
38
Where do endocrine glands occur?
Discretely in specific organs
39
What type of exocrine gland is a goblet cell?
Unicellular
40
What are multicellular exocrine glands?
Glands that extend from epithelial surface into connective tissue
41
How can exocrine glands be classified?
Epithelial components
| Mode of secretion
42
How does the proliferation of glandular cells of mucous membranes compare to that in the liver, thyroid and pancreas?
Mucous membranes: multiply throughout life
| Liver, thyroid and pancreas: cease to multiply ~puberty unless injured
43
What is a malignant neoplasms derived from glandular epithelium?
Adenocarcinoma
44
How may multicellular exocrine gland ducts become obstructed?
Store
| Disease
45
What happens to epithelial cells that have rapidly reproduced?
Leave surface of development and invade underlying CT
46
What surrounds newly formed gland?
Basal lamina
47
How are glandular products synthesised and stored?
Synthesised intracellularly and stored in secretory granules
48
What is mucin?
Principle glycoprotein constituent of mucus
49
What is Alcian Blue used to stain a vivid blue?
Mucin
50
What are Lieberkühns glands?
Simple tubular structures lined by water absorptive columnar cells and goblet cells
51
What is the function of Lieberkühns glands?
As water is absorbed from gut the mucus permits adherence of solid waste into a compact mass
Protects from trauma
52
What is the structure of the duct in a simple gland?
In branched w/secretory portion that can be straight, coiled or branched
53
What are the ducts in a compound gland like?
Repeatedly branched
54
What is an acinus?
Sac-like cavity in a gland which is surrounded by secretory cells that are grouped to give lobes
55
What type of glands might acini be found in?
Acinar
Tubular
Tubuloacinar
56
What is the function of mucous secretions?
Lubrication
| Protection of inner lining of organs
57
What are serous secretions often rich in?
Enzymes
58
What type of secretion do mixed glands release?
Serous and mucous
59
What is merocrine secretion?
Exocytosis w/out loss of cellular components
60
What is holocrine secretion?
Cells themselves become secretory products
61
What is apocrine secretion?
Part of secretory cell is released as product
62
Give an example of an apocrine gland.
Mammary
63
Where is the parotid gland located?
Below and in front of each ear
64
How is the parotid gland classified?
Entirely serous exocrine gland of acinar type
65
How does the parotid gland store its secretions?
Zymogen granules in apical cytoplasm of its acinar cells
66
Where does the principal duct of the parotid gland open?
Onto inner side of cheek opposite second upper molar
67
What is the hypotonic saliva secreted by the parotid gland rich in?
Salivary amylase
| IgA
68
Where are myoepithelial cells found in glandular epithelium?
Above basement membrane below luminal cells
69
Where does the submandibular gland release its secretions?
Floor of mouth each side of frenulum
70
What are large multicellular glands surrounded by?
Connective tissue that send septa into gland to divide into lobes and lobules
71
What forms a demilune?
Serous cells that cap mucous cells
72
How do serous enzymes from demilunes in the sublingual salivary glands reach acinar lumen?
Canaliculi b/w mucous cells
73
How are endocrine glandular cells arranged in the thyroid?
Secretory products stored and modified extracellularly in the central lumen of follicles which are lined by glandular cells
74
How do adipose cells in glands change with time?
Occupy an increasing amount of space w/age
75
How many embryological origins do the adrenal glands have?
2
76
What do all cells of the adrenal glands contain?
Lots of SER
| Mitochondria w/lots of cristae
77
What are the layers of the adrenal glands from outside to inside?
Outer capsule
Zona glomerulosa
Zona fasciculata
Zona reticularis
78
What is secreted by the zona glomerulosa?
Mineralocorticoids - primarily aldosterone
79
What is the function of aldosterone?
Increase sodium and water retention --> increase blood pressure
80
What does the zona fasciculata secrete?
Glucocorticoids - principally cortisol
81
What does the zona reticularis secrete?
Androgens
82
What is the function of glucocorticoids?
Affect most tissues for carbohydrate, protein and lipid metabolism
83
What is the function of androgens?
Weak masculinising hormones
84
What do the modified sympathetic nerve cells of the adrenal medulla lack?
Dendrites and axons
85
What blood supply does the adrenal medulla have intimate contact with?
Arterial and blood drained through cortex
86
What are hormones made from in the zona glomerulosa?
Cholesterol
87
How are cells in the zona fasciculata arranged?
Parallel cords perpendicular to adrenal capsule
88
How are the cells arranged in the zona reticularis?
Branching cords or clusters separated by wide capillaries
89
How are chromaffin cells arranged in the adrenal medulla?
Clusters or short cords
90
How do cells in each of the layers of the adrenal cortex compare?
ZG: less cytoplasm than in ZF
ZF: more cytoplasm w/lipid droplets, large pale cells
ZR: smaller
91
What do chromaffin cells release upon nervous stimulation along with catecholamine hormones?
Enkephalins
92
What are enkephalins?
Opioid peptides involved in pain control
93
What is the usual structure of the parathyroid gland?
4 small ovoid structures on the posterior wall of the thyroid
94
What is the parathyroid gland composed of?
Masses and cords of epithelial cells supported by reticular fibres and a rich network of capillaries
95
What is the function of each of the cells in the parathyroid gland?
Chief/principal cells: parathyroid hormone
| Oxyphil: uncertain (maybe inactive chief cells)
96
What are the excretory ducts of the exocrine pancreas lined by?
Simple columnar epithelium w/occasional goblet cell
97
What does the exocrine pancreas secrete?
Digestive enzymes and proenzymes
98
What passage do the exocrine secretions from the pancreas take?
Form closely packed secretory acini
Drain into highly branched duct system
Into duodenum
99
What do each of the cells of the endocrine pancreas secrete?
Alpha - glucagon
Beta - insulin
Delta - somatostatin
100
What is the special feature seen in the endocrine pancreas?
Islets of Langerhans
101
What is the distinguishing characteristic of the pancreas?
Terminal of duct w/in acinus consists of centro-acinar cells, often seen in the acinar lumen
102
Where is the pancreas situated?
Behind stomach with one end in curve of duodenum
103
What are the 2 major exocrine secretions of the pancreas?
Trypsinogen and ribonuclease
104
What are the 2 major endocrine secretions of the pancreas?
Insulin and gastrin
105
Where is HCl produced in the GI tract?
Parietal cells of stomach
106
What is the limit of resolution?
Minimum distance at which two objects can be distinguished
107
What is the relationship between the limit of resolution and wavelength?
Limit of resolution improves as wavelength decreases
108
What are the 10 components of a eukaryotic cell?
```
Cytosol
Golgi apparatus
Lysosome
Mitochondrion
Nuclear envelope
Endoplasmic reticulum
Nucleolus
Nucleus
Peroxisome
Endosome
```
109
Why does the Endosome have an interior pH of 6?
Proton pumps in membrane
110
What forms late endosomes?
Endosome uncouples receptors from ligand, receptor is recycled and ligand retained
111
What do endosomes mature into when their pH decreases?
Lysosomes
112
What is the structure of a peroxisome?
Roughly spherical w/granular matrix and single membrane
113
Why is the replication of peroxisomes odd?
Self-replicate but have no genome
114
Why are peroxisomes found in all cells, especially liver and kidney cells?
Detoxification
115
How do peroxisomes oxidise about 50% of consumed alcohol?
Use oxygen to form hydrogen peroxide which can oxidise other substrates incl. alcohol
116
What is contained in the nucleus?
DNA, nucleoproteins and RNA
117
What does TEM show in the nucleus?
Electron dense heterochromatin and electron-leucent euchromatin
118
Why is there no nucleus in erythrocytes, stratum corneum and kens fibre cells?
Terminally differentiated
119
Which form of chromatin is active in RNA?
Euchromatin
120
What happens in the nucleolus?
Ribosomal RNA synthesis
Ribosomal subunits exported
Disappear during cell division
121
The nuclear envelope is a double layer of what?
Specialised ER
122
What is between the inner and outer nuclear membrane which is continuos with the ER?
Perinuclear cisternae
123
What are nuclear pores guarded by?
Nuclear pore complexes
124
What forms the endoplasmic reticulum?
Interconnecting membranes, vesicles and cisternae
125
What is the function of smooth endoplasmic reticulum?
Lipid biosynthesis
| Intracellular transport - steroid production
126
Where do vesicles bud off from and fuse to?
Bud off from RER and fuse w/convex forming face of Golgi body
127
What does the Golgi apparatus have to ensure that proteins migrate from convex to concave end?
Polarity
128
What is the function of the Golgi apparatus?
Sort, concentrate, package and modify proteins from RER
129
What does the lysosome contain?
Acid hydrolase said at pH 5
130
What modification do the lysosomal membrane proteins have?
Glycosylated
131
How are primary lysosomes identified?
Enzyme content
132
How are secondary lysosomes formed?
Primary lysosomes fuse w/ phagosomes/endosomes/autophagosomes or excess secretory product
133
What are residual bodies?
Indigestible remnants in lysosomes
134
Describe the structure of a mitochondrion.
Variable shape
| Double membrane - inner folded into cristae
135
What is the function of the mitochondria?
Oxidative phosphorylation using glucose and fatty acids
136
What is present in the mitochondrial matrix?
```
Enzymes of Krebs and fatty acid cycles
DNA
RNA
Ribosomes
Calcium granules
```
137
What lineage do mitochondria follow?
Female - all from mum
138
What makes up the cytoskeleton of cells?
Microfilaments
Intermediate filaments
Micro tubules
139
What is the function of the cytoskeleton?
Structural support
Contractility in cells of specialised tissues
Locomotor mechanisms - intercellularly and cilia, flagella etc.
Maintain/change cell shape
140
What forms microfilaments?
2 actin filaments twisted together associated w/ATP
141
Why are Microfilaments said to be dynamic?
Actin filaments can assemble and dissociate
142
What helps keep intestinal microvilli shape?
Core of microfilaments
143
Are intermediate filaments dynamic?
Nope
144
Where are intermediate filaments found?
Nerve cells
Neuroglial cells
Epithelial cells made of cytokeratin
145
What is the structure of microtubules?
13 alpha and beta subunits polymerise to form wall of a hollow microtubule
146
Where do micro tubules originate from?
Centrosome
147
Where are micro tubules found?
Where structures move e.g. nerve fibres, mitotic spindle, cilia and flagella cores
148
What basic structure do all cell membranes have?
Phospholipid bilayer
149
How are proteins organised in the cell membrane?
Many freely mobile within bilayer
Some attached to cytoskeleton
Many glycosylated
150
What is the outermost bounding membrane called?
Plasmalemma
151
What is the glycocalyx?
Cell coat made up of oligosaccharide and polysaccharide sidechains of glycoproteins and glycolipids
152
What is the function of the cell membrane?
```
Intercellular adhesion and recognition
Signal transduction
Compartmentalisation
Selective permeability
Transport along cell surface
Endo/exocytosis
```
153
Where can pseudostritified epithelium found?
Lumina of epididymis
Respiratory passages
Lumen of vas deferens
154
Which parts of the cell does haemotoxylin and eosin?
```
Acidic = purple/blue
Basic = pink
```
155
What staining is used for classification of bacteria?
Gram staining
156
What staining is used for TB and leprosy?
Acid fast
157
Which cell components does gram staining stain violet?
-ve
158
Which type of bacteria stain violet with gram staining?
Gram +ve
159
What colour do gram -ve bacteria stain?
Red
160
What do gram +ve bacteria have more of than gram -ve?
Peptidoglycan wall
161
What shapes of bacteria are there?
Cocci - spherical
Bacilli - elongated
Coccobacilli
162
What internal structures are unique to bacteria?
Spores
| Inclusion granules
163
Which external structures are unique to bacteria?
```
Fimbriae
Pili
Flagellae
Cell capsule
Cell envelope
```
164
What is the outer membrane of a bacterium made from which makes it toxic?
Lipo-polysaccharide
| Phospholipids
165
What can spores resist?
Boiling
| Many disinfectants
166
What are mycoplasmas?
Bacteria with no peptidoglycan wall
167
What do gram negative bacteria have in their outer membrane which stimulates a strong immune response?
Lippolysaccharides
Lipoglycans
Endotoxin
168
How can bacteria be grown for identification?
Broth
Colonies
Bio films
169
How are bacteria measured in growth in broth?
Measured in turbidity
170
What are endogenous bacteria?
From body's own microbiome
171
Which type of bacteria are dominant in the body?
Anaerobes
172
What are facultative bacteria?
Have both aerobic and anaerobic function
173
Give two examples of gram +ve cocci.
Staphylococcus
| Streptococcus
174
Give an example of gram -ve cocci.
Neisseria
175
Give an example of a gram +ve bacilli
Clostridium
176
Give four examples of gram -ve bacilli.
Eschericha
Pseudomonas
Salmonella
Legionella
177
Which major groups form prokaryotes?
Bacteria
| Archae
178
Which major groups form eukaryotes?
Fungi
| Protozoa
179
Compare the number of chromosomes in prokaryotes and eukaryotes.
Prokaryotes: 1
Eukaryotes: many
180
How do the ribosomes compare in prokaryotes and eukaryotes?
Prokaryotes: 30S + 50S subunits - 70S ribosome
Eukaryotes: 40S + 60S subunits - 80S ribosome
181
What is infection?
Establishment of an organism in or on a host that multiplies and causes damage/dysfunction
182
What determines whether individuals get particular infections?
Epidemiology
Virulence vs host resistance
Innate and adaptive immunity
183
What influences the outcome of infection?
Encounter dose and route
Virulence vs host resistance
Innate and adaptive immunity
Timely diagnosis and treatment
184
What are Negritos bodies?
Visible artefacts in neurons infected by Rabies
185
Describe the genetic information in a virus.
No genes for protein
| Have RNA or DNA, not both
186
What are enveloped viruses?
On the way out of the cell some viruses pick up a lipid envelope for protection - contain lipids unlike naked viruses
187
What is used to classify viruses?
Nuclei can acids
188
What can viruses do in bacteria?
Alter antibiotic resistance
189
What is positive sense in single stranded RNA?
gRNA can serve as mRNA and be directly translated into protein
190
What is negative sense in single stranded RNA?
gRNA cannot be RNA so has to become +ve before it can be read
191
What are the phases of a colony number vs time curve for bacteria?
Lag
Log
Stationary
192
How does the curve for virus number vs time compare to that of colony number versus time for bacteria?
Virus has steeper increase and reaches plateau much faster
193
Why do RNA viruses mutate at a much higher rate than DNA viruses?
RNA polymerase cannot proofread like DNA polymerase
194
Why is HIV so difficult to treat?
Enveloped by host cell membrane so looks like host
195
What mechanisms do immunisations use?
Interfere with receptor binding
196
What is meant when a cell is said to be permissive for a virus?
A virus can successfully replicate in the cell due to it having the necessary cellular machinery
197
What is the Baltimore scheme?
How the viral genome enters the host cell
198
What kind of processes are usually used to convert viral genome?
Translational that don't usually occur in eukaryotic mammalian cells
199
Give three examples of an enveloped DNA virus.
Hepatitis B
Herpes virus
Smallpox
200
Give an example of non-enveloped viruses.
Papillomaviruses
201
Give four examples of enveloped RNA viruses.
Rubella
Rotavirus
HIV
Coronavirus
202
Give an example of a class of non-enveloped RNA viruses.
Picornaviruses
203
What often happens on release of virus from a cell?
Cellular death
204
What cytopathic effects are visible due to viral replication?
Inclusion bodies
Syncytia formation
Chromosomal damage
Inhibition of host cell protein, RNA or DNA synthesis
205
What do RNA retroviruses have that allows them to cause cancer?
Reverse transcriptase
206
How do DNA viruses cause cancer?
Inactivate tumour-suppressor proteins in non-permissive cells
207
What binds to receptors on the CSM in Ebola infection?
Glycoproteins on filovirus surface
208
Why is Ebola so destructive to the body?
Immune cells become disordered as the body knows it needs to get rid of something but it cannot determine what
209
Which sense if as RNA does Ebola have?
-ve
210
Which type of viruses are harder to get rid of?
Non-enveloped
211
Which type of virus survives less well outside of cells?
Enveloped
212
What is the general structure of a virus?
Nuclei can acid core surrounded by capsid
213
Give an example of a viral infection that must be reported by law.
Meningitis
214
How is viral infection curtailed within host?
Cell-mediated immunity
215
What classes of virus are there based on their timescale?
Acute
Subacute
Chronic
Latent
216
How can viral infection be detected?
Particles or antigens in tissue specimens
Specific virus-directed immune response
Cell culture
Genome directed nuclei can acid amplification
217
How is viral infection characterised?
Incubation period in which replication leads to symptomatic damage/dysfunction
218
How can viral infection be acquired?
Vertical transmission
Sexual contact
Respiratory
Transcutaneous (inoculation)
219
What is the pre-embryonic period?
First two weeks of development after fertilisation
220
What does the hypothalamus produce which acts on the anterior lobe of the pituitary gland to stimulate release of gonadotropins?
Gonadotrophin-releasing hormone
221
What does FSH stimulate?
15-20 follicles to grow so that one can mature and discharge an oocyte
222
What does oestrogen production stimulate?
Uterine endometrium enters proliferative phase
Cervical mucus thins to allow passage of sperm
Anterior lobe of pituitary gland stimulated to secrete LH
223
When is the oocyte arrested in meiosis?
~3hrs before ovulation
224
What happens in ovulation?
Oocyte arrested in meiosis
Ovary surface bulges locally
LH surge break collagen fibres an causes ovarian wall contractions
Oocyte and granulosa cells break free
225
What propels the oocyte post ovulation?
Peristaltic contractions and cilia in tubal mucosa
226
What stage does the uterine mucosa enter ready for implant post ovulation?
Progestational
227
What happens if there is no fertilisation of the oocyte released in ovulation?
Progesterone production decreases and menstrual bleeding ensues
228
Where is hCG secreted from?
Syncytiotrophoblast
229
What happens if progesterone secretion is removed before the end of the fourth month of development?
Abortion
230
How long are the oocyte and sperm viable for?
```
Oocyte = 1 day
Sperm = up to 3 days
```
231
Where does fertilisation usually occur?
Ampulla
232
What two processes must the sperm undergo to fertilise the oocyte?
Capcitation
| Acrosome reaction
233
What is the function of the acrosome reaction?
Release of zona pellucida penetrating enzymes
234
What are the 3 stages of fertilisation?
Penetration of Corona Radiata
Penetration of Zona Pellucida
Fusion of gamete membranes
235
What happens upon fusion of the gamete membranes in fertilisation?
Prevention of polyspermy
Meiosis II resumed
Egg metabolically activated
236
Where is the ideal site of implantation of the fertilised ovum?
Psterior uterine wall
237
What are the main results of fertilisation?
Restoration of diploid number
Determination of sex
Initiation of cleavage
238
When does cleavage of the zygote begin?
30 hours after fertilisation
239
How are blast omers of equal size formed?
Mitotic divisions of the zygote produce equally sized cells which are restricted by the zona pellucida
240
What happens to the blastomeres after the third cleavage?
Compaction: maximise contact and are held together by tight junctions
241
What do the compacted embryo cells divide into?
16 cell morula
242
What can be said about the cells in the morula?
They are totipotent
243
Why do you wait for the formation of the 16-cell morula before transfer into the uterus in IVF?
Not all oocyte said will undergo cleavage
244
How is the first embryonic cavity formed in the morula?
Cells secrete fluid which pushes them to one side, creating a shell of cells
245
What does the embryoblast give rise to?
Embryo proper
246
What does the trophoblast give rise to?
Supportive tissues
247
When does the first true differentiation of embryonic cells occur?
Following compaction where they change from totipotent to pluripotent
248
What is the outer cell mass of the blastocyst called?
Trophoblast
249
What is the inner cell mass of the blastocyst called?
Embryoblast
250
What is the blastocele?
Blastocyst cavity
251
What hatches from the zona pellucida once the risk of polyspermy has been retracted?
Blastocyst
252
What can happen to the blastocyst once it has hatched from the zona pellucida?
Free to enlarge
| Interact w/ uterine surface to implant
253
What is the most important event in the pre-embryonic period of development?
Implantation
254
How are the 107 cells of the conceptus present at the initiation of implantation distributed?
8 embryo
| 99 foetal membranes
255
What do the pre-embryonic and early embryonic periods prioritise in development?
Development of placenta
256
What gives rise to two distinct cellular layers in the week of twos during embryonic development?
Differentiation
257
What does the outer cell mass divide into during differentiation?
Syncytiotrophoblast
| Cytotrophoblast
258
What does the inner cell mass become during differentiation in embryonic development?
Bilaminar disc
259
What types of cells make up the bilaminar disc?
Columnar epiblast
| Cuboidal hypoblast
260
Which layer of the bilaminar disc is most important for tissue development?
Epiblast
261
Where are the epiblast and hypoblast located?
Epiblast: adjacent to amniotic cavity
Hypoblast: adjacent to blastocyst cavity
262
How do the cells of the syncytiotrophoblast appear?
Multinucleated w/no distinct cell borders
263
What do the syncytiotrophoblast and cytotrophoblast give rise to?
Syncytiotrophoblast: transport/support tissues
Cytotrophoblast: true epithelium
264
How do the cells of the cytotrophoblast appear?
Almost simple cuboidal
| Mononucleated
265
What heals the site of the blastocyst once physical implantation has completed?
Fibrin plug
266
What can happen during implantation which causes confusion when calculating the due date?
Bleeding
267
What forms the primitive yolk sac?
Multiplication of the hypoblast lining the blastocyst cavity
268
What is the primitive yolk sac in contact with?
Cytotrophoblast layer
269
What happens to the yolk sac which produces a slight protusion into the lumen of the uterus?
Pushed away by acellular extraembryonic reticulum which is later converted to mesoderm
270
How does the uteroplacental circulation begin?
Maternal sinusoids invaded by syncytiotrophoblast
Lacunae become continuous w/sinusoids
Uterine stroma becomes incredibly vascular
271
How is the secondary yolk sac formed?
Pinches off from primitive yolk sac
272
What is the importance of the formation of the definitive yolk sac?
V. important for GI tract development
273
How is the chorionic cavity formed?
Spaces in extraembryonic mesoderm merge
274
What does the column of mesoderm which will later form the umbilical cord suspend?
Embryo and cavities
275
What is the name of the column of mesoderm which will later become the umbilical cord?
Connecting stalk
276
What are the end results of week two of development?
Conceptus has been implanted
Embryo and two cavities formed
Embryo and cavities suspended by connecting stalk w/in supporting chorionic activity
277
What are the two cavities present at the end of week of two in embryonic development?
Amniotic cavity
| Yolk sac
278
What aids breach of the uterine epithelium by the conceptus during implantation?
Proteolytic enzymes
279
How does blood supply to the conceptus change during implantation?
Histiotrophic --> haemotrophic
280
What is IUGR?
Inter Utrinine Growth Restriction, suggests suboptimal establishment of maternal-foetal exchange
281
What fails to happen in embryonic development which leads to pre-eclampsia at 20+ weeks?
Differentiation of cytotrophoblast cells from epithelial --> endothelial cells
282
What is ectopic pregnancy?
Site of development other than uterine body
283
Why can ectopic pregnancy be incredibly dangerous?
Can cause fatal haemorrhage before the pregnancy is discovered
284
What is placenta praevia?
Implantation in lower uterine segment leading to placental obstruction --> requires C-section
285
What percentage of all zygotes are lost in the first 2-3 weeks of development before the pregnancy is discovered?
~50%
286
What percentage of women suffer recurrent (3 consecutive) miscarriage?
1%
287
What are the functions of connective tissue?
```
Provide substance and form to body organs
Provide medium for diffusion
Attach muscle to bone and bone to bone
Provide cushioning
Defend against infection
Aid in injury repair
```
288
Why does dense connective tissue have a long healing time?
Avascular
289
What are the components of connective tissue?
Cells
Extracellular matrix
Fibres
290
What forms the ground substance?
Hyaluronate proteoglycan aggregates
291
What types of fibres may be present in connective tissue?
Collagen
Reticular
Elastic
292
How is connective tissue classified?
Mesenchyme
Dense
Areolar (loose)
Specialised
293
Where is irregular connective tissue seen?
Dermis
Organ capsules
Areas needing strong support
294
Where is dense regular connective tissue seen?
Tendons
| Ligaments
295
Where is areolar tissue found?
Adipose tissue
296
What cells are present in areolar connective tissue?
Macrophages
Fibroblasts
Mast
297
Give some examples of specialised connective tissue.
```
Blood
Cartilage
Bone
Haemopoietic
Lymphatic
```
298
What are the different mesenchymal cells in different tissues?
Osteoblasts in bone
Myoblasts in skeletal muscle
Fibroblasts in supporting tissues
Chrondroblasts in cartilage
299
Why does mesenchymal tissue persist in the adult for healing?
Cells are pluripotent
300
What makes up ground substance?
Hyaluronic acid
Glucosaminglycan
Collagen fibrils
301
What forms hyaluronate proteoglycan aggregates?
Hyaluronic acid
| Glucosaminoglycan
302
How do hyaluronate proteoglycan aggregates form a gel?
Negative charge attracts water
303
What is the function of the gel part of ground substance?
Barrier
| Diffusion of water soluble molecules b/w cells and BV
304
What does fibronectin bind to?
Cells
Collagen
Proteoglycans
305
What do integrins bind to?
Cells
| Extracellular collagen
306
What does laminin bind to?
Epithelial cells
| Basal lamina
307
Which type of collagen accounts for 90% of all collagen in the body?
I
308
Which type of collagen is found in hyaline cartilage?
II
309
Do type II collagen fibrils form fibres?
Nope
310
What is another name for type III collagen?
Reticulin
311
Where do type III collagen fibrils form fibres?
Around muscle and nerve cells w/in lymphatic tissues and organs
312
What is type IV collagen?
Unique form of collagen present in basal lamina of the basement membrane
313
What is the dominant cell type in connective tissue?
Fibroblasts
314
What do fibroblasts synthesise?
Collagen
Reticular fibres
Elastic fibres
Carbohydrates of ECM
315
What lays down procollagen?
Fibroblasts
316
What are fibrocytes?
Spindle shaped more mature and less active fibroblasts
317
What cellular components are fibroblasts rich in?
Euchromatin
| RER
318
What cells are found in connective tissue?
```
Fibroblasts/cytes
Plasma cells
Adipose
Small and large lymphocytes
Macrophages
Eosinophils
Neutrophils
Mast cells
```
319
Do collagen fibres branch?
Nope
320
Describe the structure of elastic fibres.
Thin, small, branching that recoil w/out deformation
321
What is the structure of arteries from the lumen outwards?
Tunica intima
Tunica media w/smooth muscle
Tunic adventitia
322
Where are elastic fibres found?
Lungs
Bladder
Skin
Blood vessels
323
What do the smooth muscle cells in the tunica media secrete?
Elastin
Collagen
ECM
324
How are reticular fibres arranged?
Thin fibres that form a delicate net-like framework
325
Where are reticular fibres found?
Liver
Lymph nodes
Spleen
Haemopoietic organs
326
What is the function of reticular fibres?
Filter blood and lymph
| Support capillaries, nerves and muscles
327
How are the fibres in areolar tissue arranged?
Collagen predominate to form a loose fibre meshwork
Elastic fibres branch
Some fine reticular fibres (often unseen)
328
Which cells are always seen in areolar tissue?
Macrophages
329
What cells are seen in areolar tissue?
```
Mast
Eosinophils
Neutrophils
Lymphocytes
Adipocytes
Macrophages
```
330
What characteristics does areolar tissue have?
Highly vascular
| Able to stretch quite a lot
331
How are the fibres arranged in dense irregular tissue?
Bundles of collagen densely but irregularly packed
Larger and more numerous elastic fibres than in areolar CT
Fine elastic networks
332
How are fibroblasts arranged in dense irregular connective tissue?
Compressed among collagen fibres
333
What is the composition of dense irregular tissue?
Minimal ground substance
| Sparse cells other than fibroblasts
334
What characteristic does dense irregular tissue display?
Great tensile strength
335
What type of tissue divides gland into lobules to give strength?
Trabeculae of dense irregular tissue
336
How are fibres arranged in dense regular connective tissue?
Collagen bundles lie in parallel, densely packed and in line w/tensile force from muscle
337
What is the composition of dense regular tissue?
Elongated flattened fibroblasts lie b/w collagen bundles
Little ground substance
Only really fibroblasts present
338
What separates fascicles of densely packed collagen bundles in short ligaments?
Loose connective tissue
339
What is an aponeurosis?
Flat tendon
340
What happens at the myotendinous junction?
Sarcolemma of muscle fibres lies b/w collagen bundles and myofilaments
341
What does interfascicular connective tissue between large collagen bundles contain?
Blood vessels
| Pacinian corpuscles
342
What are macrophages?
Most important antigen presenting cells and phagocytic cells derived from blood monocytes in the tissue
343
What do the abundant granules in mast cells contain?
Heparin
Histamine
Eosinophil and neutrophil attractors
344
What are mast cells not seen in the CNS?
Avoid oedema formation here
345
What causes release of mast cell contents?
Cross-linking of coating IgE by an allergen
346
What causes immediate hypersensitivity reactions, allergy and anaphylaxis?
Release of mast cell contents
347
What can early lipoblasts, derived from fibroblasts, mature into?
White or brown adipocytes
348
What is the structure of a white adipocyte?
Multiple lipid droplets fuse to form one large one that pushes cell contents to the periphery
349
What is the structure of brown adipocytes?
Multiple lipid droplets w/central nuclei
350
Which type of adipose tissue has a rich vascular supply and lost of mitochondria?
Brown
351
What type of adipose tissue is involved in non-shivering thermogenesis in babies and hibernating animals?
Brown
352
What is vitiligo?
Symmetrical autoimmune attack of melanocytes
353
What is alopaecia areata?
Autoimmune attack of hair follicles causing hair loss
354
How can the skin vary in macroscopic structure?
Laxity/wrinkling
Hair
Colour
355
What causes ageing in the skin?
UV-induced injury to dermal collagen and elastin
356
Where is ageing in the skin more prominent?
Areas that flex a lot
357
Which is the thicker component of the skin?
Dermis
358
What does the dermis contain?
Blood vessels
Erector pili muscles
Sweat glands
359
What are the layers of the epidermis from top to bottom?
Horny
Granular
Prickle
Basal
360
What function do the flattened corneocytes in the horny layer of the epidermis perform?
Major skin barrier
| Water barrier
361
What does the granular layer of the epidermis contain?
```
Keratohylin granules
Fibrous proteins
Phopsholipase
Fillaggrin
Involucrin
```
362
What is the function of fillaggrin?
Aggregates keratin
363
What is seen in the granular layer of the epidermis which is a major part of the corneocytes envelope?
Involucrin
364
Why is the prickle cell layer of the epithelium so called?
Cells are joined by prickle like desmosomes
365
How does a keratinocytes progress through the epithelium?
Mitosis in basal layer
Daughter keratinocytes move to prickle cell layer and cannot divide
Lose plasma membrane and become corneocytes in granular layer
Corneocytes are main cells of horny layer
366
How long does cell migration through the epidermis take?
30-40 days
367
Does the number of melanocytes in different skin types change?
No, production of melanin does
368
In which layer of the epidermis are melanocytes found?
Basal
369
What type of cells are melanocytes?
Dendritic of neural crest origin
370
What are Langerhans cells highly specialised to do?
Present antigens to T-lymph
371
What type of cells are Langerhans cells?
Dendritic of bone marrow origin
372
Which layer of the epidermis are Langerhans cells seen in?
Prickle
373
What mediates immune reactions in the epidermis?
Langerhans cells
374
What aggregates around the nucleus of epithelial cells to protect against UV?
Neighbouring keratinocytes w/donated melanin from melanosomes
375
What are melanosomes?
Mature melanocytes containing melanin
376
What is psoriasis?
Extremes proliferation of epidermal basal layer --> gross thickening of prickle cell layer --> excessive stratum corneum cell production --> scaling
377
What causes psoriasis?
Don't know
378
What mediates allergic contact dermatitis?
Langerhans cells
379
What is the difference between a malignant melanoma with a good prognosis and one with a poor prognosis?
Tumour cells above BM = good
| Penetrating 'nodular' melanomas = very poor
380
What is the dermo-epidermal junction?
Site of epidermal basement membrane below basal layer of epidermis
381
How is the dermis characterised?
Tough
Fibrous
Vascular
382
What shape are fibroblasts in the dermis?
Spindle shaped throughout
383
What is found in the ECM of the dermis?
Collagens esp. type I
Elastin
Other ECM components
384
What components are found in the dermis in addition to the ECM?
Blood vessels
Lymphatic vessels
Mast cells
Nerves
385
What is solar elastosis?
Collagen and elastin damage due to excessive UV exposure
386
What causes striae?
Damage to collagen and elastin
387
What do scars comprise of?
Mainly collagen from fibroblasts
388
What predisposes to keloid formation?
Coloured skin
389
How is blood supplied to the skin?
Smaller blood vessels in superficial dermis interconnecting vessels larger blood vessels in deeper dermis
390
What is a birthmark?
Congenital malformation of dermal blood vessels
391
What happens in acne?
Abnormal differentiation of sebaceous gland ducts which become obstructed
Increased sebum production leads to infection by normally harmless skin bacteria
392
What method of secretion do sebaceous ducts use?
Holocrine
393
What is the function of eccrine sweat glands?
Thermoregulation
394
How are eccrine swear glands classified?
Simple, coiled, tubular glands w/clear cells that secrete watery substance and dark cells that secrete mucus
395
What aids expulsion from eccrine sweat glands?
Myoepithelial cells
396
What does hyperhidrosis cause?
Wet, malodorous feet and embarrassing wet palms
397
What are apocrine sweat glands?
Large sweat glands w/no known function
398
Where are apocrine sweat glands abundant?
Axillae
Genital area
Submammary area
399
What causes body odour?
Cutaneous microbes digesting protein-rich apocrine secretion from apocrine sweat glands
400
What are the main functions of the skin?
Barrier
Thermoregulation
Sensation
Psychosexual communication
401
What does the skin act as a barrier to?
Loss of fluid, protein, other nutrients and heat
| Excessive absorption of potentially harmful exogenous agents
402
Name two conditions that can cause sensory neuropathy.
Diabetes
| Leprosy
403
What are paramount in thermoregulation?
Vasculature
| Eccrine sweating
404
What is the overall function of the embryonic period?
Right number of cells of the right type in the right place
405
When is the embryonic period?
Weeks 3-8
406
Which is the period of greatest change in embryonic development?
Embryonic
407
When are all major structures and systems during development?
Embryonic period
408
Which is the most perilous stage for the developing child?
Embryonic period
409
What happens in the week of threes in the embryonic period of development?
3 cavities - chorionic cavity established
Trilaminar disc - 3 germ layers
3 axes set
410
What are the 3 axes set during the embryonic period?
Anterior/posterior
Dorsal/ventral
Right/left
411
What is the legal significance of the primitive streak?
Cannot clone an embryo after it has appeared
412
What appears on the dorsal surface of the epiblast during gastrulation?
Narrow groove w/bulging edges
413
Where are the primitive node and pit located during gastrulation?
```
Node = cranial end
Pit = centre of node
```
414
What is the conductor of gastrulation?
Primitive node
415
What happens to the primitive streak during gastrulation?
Regresses, moving cranial to caudal
416
Why is the cranial end of a developing embryo always more developed than the caudal?
Primitive streak regression
417
What happens to the hypoblast cells in migration and invagination?
Lost as no longer needed
418
What do the epiblast cells lateral to the primitive streak undergo when they move into it?
Epithelial to mesenchymal transformation
419
How do the cells change in appearance in epithelial to mesenchymal transformation?
Cuboidal, tightly connected --> irregularly shaped, loosely connected
420
Which layer of the trilaminar disc is formed by invasion and displacement of hypoblast cells?
Definitive endoderm
421
Which layer of the trilaminar disc is formed by invasion between epiblast and definitive ectoderm?
Mesoderm
422
Which five subgroups can the mesoderm be split into?
```
Vascular system
CT
Body cavity linings
RBCs
Muscle
```
423
Which layer of the trilaminar disc is formed by the remaining epiblast quickly differentiating?
Ectoderm
424
Which tissues are derived from the ectoderm?
```
Organs of special senses
Pigment cells
Epidermis
Neurons
CNS
```
425
How do the cells in the mesoderm spread out?
Laterally and cephalad
426
Where does the ectoderm fuse tightly with the endoderm?
At two faint depressions, one at the cranial end and one at the caudal end
427
What will the tight fusions of the ectoderm and endoderm become in the developing embryo?
Mouth and anus
428
What forms the notochord?
Subgroup of mesodermal cells that migrate cranially to form a thick-walled midline tube
429
Where is the notochord located?
In the midline running from the head through the embryo
430
What is the importance of the notochord?
```
Important signalling role
Defines midline
Defines axial skeleton
Drives neurulation
Regresses into nucleus polposus
```
431
What is a slipped disc?
Herniation of nucleus polposus
432
Which axis is defined by the primitive streak?
Rostral/caudal
433
What ensures correct dorso-ventral and left-right development?
Molecular signals emanating from primitive node
434
What causes left-right asymmetry as seen in the neonate?
Action of ciliated cells at primitive node gives left-ward flow of signal, absence of which gives right sided structures
435
When is the embryonic disc bilaterally symmetrical?
Before gastrulation
436
What is situs inversus?
Immobile cilia or chance causes lack of left-sidedness signal so major visceral organs appear on reflected side
437
When do problems arise in situs inversus?
Faulty cilia
| If normal and mirror image disposition occur together
438
Why is gastrulation not complete until week 4?
Development proceeds cephalocaudally so not complete in caudal region until then
439
How are twins formed with their own individual placenta?
Embryo splits after first cleavage
440
How can twinning occur with two embryos sharing the same placenta?
Inner cell mass duplicated and slightly separated
| Duplication of primitive streak --> 2 gastrulation events and primitive streaks
441
How are conjoined twins formed?
Separation not complete following duplication of inner cell mass
442
What is teratogenesis?
Process by which normal embryonic development is disrupted
443
When is the developing embryo most sensitive to teratogenesis?
Weeks 3-8 but each organ has its own specific window
444
Give examples of teratogenic agents.
```
Thalidomide
Rubella
Alcohol
Warfarin
ACEI
```
445
What is cartilage?
Avascular tissue that consists of chondrocytes within extensive extracellular matrix
446
What permits ready diffusion of substances in the extracellular matrix of cartilage?
Large ratio of GAGs to type II collagen
447
What is the benefit of having extensive extracellular matrix in cartilage?
Makes it pliable so it is resistant to repeated application of pressure
448
What are the three types of cartilage?
Hyaline
Elastic
Fibro
449
What does the ECM of hyaline cartilage contain?
Proteoglycans
Hyaluronic acid
Type II collagen
Hyaluronate proteoglycan aggregates bound to fine collagen matrix fibres
450
What is the advantage of having highly hydrated hyaline cartilage?
Permits resilience to varying pressure loads
451
What type of cells are found in hyaline cartilage?
Exclusively chondrocytes
452
How are the chondrocytes in hyaline cartilage arranged?
Singly or recently divided isogenous groups
| Separate as they elaborate
453
Which is the most common type of cartilage?
Hyaline
454
What forms the ECM of elastic cartilage?
Same as hyaline w/ elastic fibres and lamellae
455
Does elastic cartilage calcify?
No
456
What does the ECM of fibrocartilage contain?
Same as hyaline w/an abundance of type I collagen
457
What cells are present in fibrocartilage?
Chondrocytes and fibroblasts
458
Which type of cartilage is the most resistant to shearing?
Fibrocartilage
459
Is there a perichondrium in fibrocartilage?
No
460
How are the cells in fibrocartilage arranged?
Chondrocytes in rows
| Fibroblasts few and far between
461
What is the structure of the perichondrium of hyaline cartilage?
Vascularised, dense irregular w/many elongate fibroblast-like cells which can develop into chondroblasts
462
What produces and maintains the ECM of hyaline cartilage?
Chondrocytes
463
How can differentiation of chondrocytes be seen in hyaline cartilage?
Cells get bigger
464
Where is perichondrium not present?
Joint articulating surfaces
465
Why is there no perichondrium present on the articulating surfaces?
It is delicate and would be damaged
466
What is seen on hyaline that contributes to the developing joint capsule?
Perichondrium
467
What is the difference between territorial matrix and interterritorial matrix?
Territorial surrounds isogenous groups and chondrocytes and is more sulphated
468
How does hyaline cartilage grow?
Apposition all growth --> chondrocytes divide --> isogenous groups --> interstitial growth --> isogenous groups separate
469
What is an enthesis?
Point of transition b/w tendon and bone
470
How are cells arranged in the intervertebral discs?
Chondrocytes in rows or isogenous groups
| Small number of elongated fibroblasts
471
Which type of collagen is found in the menisci of the knee?
I
472
What does each chondrocyte lie in?
Lacuna
473
What stimulates chondrocytes to synthesise ECM?
Pressure loads applied to cartilage creating mechanical, electrical and chemical signals
474
What role does hyaline cartilage play in bone elongation?
Forms epiphyseal growth plate
475
Why is the bone-cartilage boundary irregular?
To prevent shearing
476
What is the structure of cancellous bone?
Forms tiny networks of fine bony columns or plates w/bone marrow filled spaces
477
Which type of bone forms the external surface of bones and comprises ~80% of body's skeletal mass?
Compact/cortical
478
How do the osteocytes appear in immature bone?
Large and randomly arranged
479
What carries blood vessels, lymph vessels and nerves in bone?
Haversian and Volkmann's canals
480
What is the structure of mature bone?
Osteocytes in concentric lamellae of osteons
| Resorption canals parallel to osteon long axis
481
What are Haversian canals?
Series of tubes that surround blood vessels and nerve cells throughout bone and communicate w/osteocytes in lacunae via canaliculi
482
What is another name for Haversian systems?
Osteons
483
What is the basic structural unit of compact bone that consists of the central canal and its concentric lamellae?
Osteons
484
What is the general direction of osteons in compact bone?
Same as that of long bone but can branch and terminate
485
What happens to Haversian systems as bone remodels?
Successive generations are formed
486
Do Volkmann's canals have concentric lamellae?
No
487
What are osteoblasts?
Cells present on surfaces of bone that synthesise, secrete and deposit osteons which is rapidly mineralised to become bone
488
What are osteocytes?
Mature osteoblasts that are the principal cells of bone trapped in matrix where they lie singularly in lacunae
489
How do osteoblasts and osteocytes differ in size?
Osteocytes are smaller
490
How do osteocytes communicate?
Canaliculi into which cytoplasmic extensions enter
491
What happens if canaliculi between osteocytes are disrupted?
Osteocytes cannot communicate so die and surrounding bone matrix is absorbed by osteoclasts
492
What are osteoclasts?
Large, multinucleated cells found along bone surfaces where resorption, remodelling and repair are taking place
493
What can osteoclasts release for bone removal?
Hydrogen ions
| Lysosomal enzymes
494
Where can elastic cartilage be found?
Pinna
Epiglottis
Auditory meatus
Eustachian tube
495
Where can hyaline cartilage be found?
```
Shoulders
Larynx
Trachea
Lung
Costal joints etc.
Skeletal model for most bones in embryo
```
496
Where can fibrocartilage be found?
```
Temperomandibular joint
Sternoclavicular joint
Intervertebral disc
Public symphysis
Menisci of knee
```
497
What gives limit to lamellae number in Haversian canals?
Connection of osteocytes via gap junctions due to absent diffusion
498
What is the composition of bone?
65% mineral - hydroxyapatite crystals
23% type I collagen
10% water
2% non-collagen proteins
499
How does the histological structure of cancellous bone differ to that of compact bone?
Osteocytes lie between irregular lamellae
No Haversian/Volkmann's canals
Adipose and haemopoietic cells lie in cavities
500
How does a bone spicule grow?
Growing spicule consists of osteocytes trapped in hard bone with surrounding osteoblasts depositing new osteoid and surrounding themselves to become osteocytes
501
What do osteoclasts create in bone remodelling?
Cutting cone that usually travels parallel to osteon direction
502
What is found behind the osteoclasts in bone remodelling?
Osteoblasts
503
What is a heterografts in relation to bone grafting?
Bone donor is a different species
504
How does bone resist fracture?
Great tensile and compressive strength coupled w/flexibility
505
What happens to the lamellae in bone before it will break?
Slip over each other
506
What are the four stages of bone healing?
Haematoma formation
Fibrocartillaginous callus
Bony callus
Bone remodelling
507
What happens during haematoma formation in bone healing?
Phagocytic cells and osteoclasts remove dead and damaged tissue
Swelling and inflammation
Blood clot forms
508
What removes the haematoma from a healing bone?
Macrophages
509
How is the fibrocartillaginous callus formed in bone healing?
Osteoblasts and multipotent cells invade
New blood vessels infiltrate haematoma
Procallus of granulation tissue develops
Fibroblasts secrete type I then type II cartilage to span break
Chondrocytes form hyaline cartilage sleeve
510
Describe the granulation tissue in fibrocartillaginous callus formation.
Rick in capillaries and fibroblasts
511
What halogens during bony callus formation?
New bone trabeculae form in callus
Callus --> cancellous bone causes tabeculae to develop into cortical bone
Emdochondral ossification replaces all cartilage w/assistance from intramembranous ossification
512
How long does bone remodelling in bone healing last?
Several months
513
What happens during the bone remodelling stage of fracture repair?
Cancellous bone --> compact bone esp. in cortical region
Bulging material is removed
Bone returns to original shape because of same stressors acting on bone
