March Formative Flashcards
The roots of which of the following permanent teeth are usually completed by the age of 11?
a) upper canine
b) upper lateral incisor
c) lower canine
d) lower second molar
e) lower second premolar
b
3 years after eruption
The tooth shown in the image is:
a) lower permanent first molar
b) upper permanent second premolar
c) upper permanent first molar
d) lower permanent second molar
e) Lower deciduous first molar
c
3 roots and a cusp of carabelli
What is the structure labelled 2?
a) mandibular process
b) maxillary process
c) oral cavity
d) frontonasal prominence
e) alae
b
Mesenchymal growth in the first brachial arch produces first the maxillary process and then the faster growing mandibular process on each side of the future face. The mandibular processes rapidly extend to the facial middle and merge. The stomodeum is now surrounded by the frontonasal process above, the paired maxillary processes either side, and the paired mandibular processes below.
What is the correct statement related to the structure labelled 2 at cap stage of tooth development?
a) enamel knot, originating from ectomesenchyme
b) dental papilla, originating from ectomesenchyme
c) dental papilla, originating from dental epithelium
d) dental sac, originating from dental epithelium
e) enamel know, originating from dental epithelium
b
The developing papilla is a condensation of ectomesenchymal cells seen in the developing tooth histology. It appears 8-10 weeks intra uterus life. The dental papilla gives rise to the dentin and pulp of the tooth.
The enamel organ, dental papilla and dental follicle together forms one unit, called the tooth germ. This is of importance because all the tissues of a tooth and its supporting structures form from thee distinct cellular aggregations. Similar to the dental follicle, the dental papilla have a very rich blood supply.
At the end of gastrulation stage of embryonic development, ectoderm is the outermost layer of the embryo and endoderm is the innermost layer, which mesoderm in between. Which of the following systems originates from the ectoderm?
a) blood
b) gastrointestinal tract
c) circulatory system
d) nervous system
e) skeleton
d
ECTODERM is one of the three primary germ layers in the very early embryo. The other two layers are the MESODERM (middle layer) and ENDODERM (most proximal layer), with the ectoderm as the most exterior (or distal) layer. It emerges and originates from the outer layer of germ cells.
The ectoderm differentiates to form the nervous system (spine, peripheral nerves and brain), tooth enamel and epidermis of skin. It also forms the lining of the mouth, anus, nostrils, sweat glands, hair and nails.In vertebrates, the ectoderm has three parts, external ectoderm, neural crest and neural tube. The latter two are known as neuroectoderm.
What is the structure labelled 1?
a) dentin-pulp border
b) gingival attachment
c) outer cortical plate
d) bundle bone
e) central spongiosa
d
- Bundle bone -bone lining the alveolus (compact bone)
- central spongiosa
- outer cortical plates
- vary in thickness
- thicker in mandible than maxilla
- thicker in premolar-molar regions
Bundle bone:
- part of the alveolar bone where periodontal ligament fibre are inserted
- bundle = bundles of fibres
- sharpeys fibres = principal fibres of the periodontal ligament that are embedded in the bone or cementum
- sharpeys fibres are seen perpendicular to the bundle bone
- other fibrils are arranged perpendicular to the bundle bone surface
- radiographically is more radio-dense due to the presence of thick bone without trabeculations called ‘lamina dura’
- alveolar bone proper has many openings for blood vessels and nerves = is perforates and is called the cribriform plate
What is the pH of a solution of 0.85M acid and 0.21M conjugate base if the pKa = 5.30?
a) 5.3
b) 4.7
c) 3.5
d) 6.7
e) 7.0
Henderson-Hasselbalch equation
pH = pKa+log(A-)/(HA)
Which of the following is a major determinant of the primary structure of a protein?
a) covalent bonding
b) ionic interactions
c) hydrophobic forces
d) hydrogen bonding
e) van der Waals forces
a
The primary structure of a protein is the sequence of amino acids in a peptide chain. The amino acids are linked by peptide bonds, which are formed by a covalent bond between the carbonyl carbon of one amino acid and the amino nitrogen of the next.
The secondary structure of a protein is a folding of a peptide chain into an alpha helix or beta pleated sheet, which are stabilised by hydrogen bonding.
The tertiary structure is the way in which the peptide chain folds upon itself.
Tertiary structures are mainly stabilised by non-covalent bonds including hydrogen bonds, hydrophobic forces, ionic interactions and Van der Waals. Tertiary structures can also be stabilised by disulphide bridges, which are covalent bonds between cysteine amino acid residues in different parts of the polypeptide chain.
The quaternary structure is where folded peptide chains join together. It is stabilised by non-covalent bonds also.
Which of the following signalling molecules does not use a cell surface receptor?
a) nerve growth factor
b) glutamate
c) acetylcholine
d) insulin
e) retinoic acid
e
Retinoic acid is a type of nuclear receptor that can also act as a transcription factor.
Glutamate is abundant in the nervous system and especially prominent in the human brain where it is the body most prominent neurotransmitter. It binds to receptors located on the cell membranes of neuronal and glial cells.
Acetylcholine binds to transmembrane cholinergic receptors, including nicotinic acetylcholine receptors and muscarinic acetylcholine receptors.
NGF and insulin bind as well to transmembrane receptors.
In an experimental solution, a giant squid is bathed in an electrolyte solution containing chloride, potassium and sodium ions. Which one of the following changes would have the greatest effect in making the membrane potential less negative?
a) increasing the extracellular concentration of K+
b) increasing the extracellular concentration of Cl-
c) decreasing the extracellular concentration of Na+
d) decreasing the extracellular concentration of K+
e) increasing the extracellular concentration of Na+
a
The resting membrane potential is determined by the uneven distribution of ions (charged particles) between the inside and the outside of the cell, and by the different permeability of the membrane to different types of ions.
Excitation-contraction coupling refers especially to the:
a. binding of acetylcholine to the motor end plate and the movement of the troponin-tropomyosin complex
b. propagation of action potentials from the neuromuscular junction to the T tubules
c. attachment of myosin cross bridges to the thin filaments
d. calcium release and binding to troponin molecules
e. events at the neuromuscular junction where a motor fibre excites a muscle cell
e
Excitation - contraction coupling in the skeletal muscle is the sequence of events through which the nerve fiber stimulates the skeletal muscle fiber causing its contraction. The cholinergic nerve fibers innervate the skeletal muscle fibers through the neuromuscular junctions, they release their neurotransmitters that cause activation of the muscle cell plasma membrane ligand gated ion channel-coupled receptors causing ion transport that in turn will activate the contractile mechanism of the muscle fiber.
In this medium-sized peripheral nerve, F labels what?
a) endomysium
b) myelin sheath
c) epicardium
d) epineurium
e) perineurium
e
The correct answer is perineurium. Three layers of connective tissue are found around nerves. Each nerve axon (C) is surrounded by the endoneurium (B). Each nerve fascicle containing one or more axons is enclosed by the perineurium (F), a connective tissue having a lamellar arrangement in seven or eight concentric layers. The epineurium (A) is the outermost layer of dense connective tissue.
Which one of the following descriptions best describes the concept of a threshold potential?
a. the membrane potential that is slightly more negative than resting membrane potential
b. the membrane potential that is slightly less negative than resting membrane potential Correct
c. the membrane potential that exists when the cell is at rest
d. the membrane potential between the 0mV and the peak amplitude of the action potential
e. the membrane potential represented by the peak of the action potential
b
The threshold potential is the critical level to which a membrane potential must be depolarized to initiate an action potential. A neuron resting membrane potential is –70 mV, while the threshold potential is a membrane potential value between -50 and -55mV.
Which one of the following best describes the role of the autonomic innervation?
a. Stimulation of the sympathetic system causes vasoconstriction in the viscera and vasodilatation in skeletal muscle Correct
b. Stimulation of the sympathetic system causes vasodilatation in the skin.
c. Stimulation of the sympathetic nerves to the eyes causes pupillary constriction
d. Stimulation of the parasympathetic system speeds up the heart.
e. Stimulation of parasympathetic nerves leads to decreased blood flow in the GI tract
a
The sympathetic system priorities blood vessels to skeletal muscles and heart (vasodilation) in terms of emergency. Stimulation of the sympathetic nervous system causes vasoconstriction of most other blood vessels, including those in the skin, digestive tract and the kidneys.
Which one of the following best describes the bonding/forces that lead to the formation of the double helix of DNA?
Select one:
a. Hydrogen bonds between bases pairs and hydrophobic stacking forces Correct
b. Ionic bonds
c. Covalent bonds between base pairs
d. Phosphate bonding
e. Covalent bonds between base pairs and hydrogen bonds between sugars
a
The two strands of double-stranded DNA are held together by a number of weak interactions such as hydrogen bonds, stacking interactions and hydrophobic effects. Of these, stacking interactions between base pairs are the most significant. The strength of base stacking interactions depends on the bases.
Base pairs [A-T, G-C ] are formed by hydrogen bonding, perpendicular to the axis of the helix. In double stranded DNA, the deoxyribose-phosphate backbone is on the outside of the molecule, the hydrophobic bases are stacked on the inside.
Which one fo the following options best describes the inheritance of a form of amelogenesis imperfecta in the family represented in the diagram?
a. X-linked recessive
b. Autosomal dominant
c. Autosomal recessive
d. Y-linked
e. X-linked dominant
b
In the pedigree, the great-great grand father (A) is affected. As the sons (e.g. B) are not affected, it cannot be Y-linked. In the next generation, none of the sons (D, E) are affected. As they have both received an X chromosome from their affected mum (C) and they are not affected, it cannot be X-linked recessive, otherwise they would be affected. If the mutation was X-linked recessive, both X-copies of the mum would bear the mutation (because the mum is affected) and each son wound inherit one of the maternal mutant X-chromosomes and would be affected. In the next generation, if the mutation was X-linked dominant, all of the daughters would be affected as they all receive a copy of their dad X-chromosome. However, one daughter (F) is not affected, hence it is not X-linked dominant. Therefore it is an autosomal mutation. If it was recessive, it would be inherited by all individuals of generation G, but it is not the case, hence it is an autosomal dominant mutation.
Select the technique you would you use to measure expression of genes in healthy versus inflamed gingiva.
a. Gene cloning of DNA
b. Quantitative Polymerase Chain Reaction (qPCR)
c. Gel electrophoresis of DNA
d. Polymerase Chain Reaction (PCR)
e. Quantitative Reverse Transcriptase Polymerase Chain Reaction (qRT-PCR)
e
PCR amplifies DNA so does not measure gene expression.
Gene cloning of DNA is used to clone pieces of DNA into a vector and so cannot measure gene expression.
Gel electrophoresis analyses sizes of DNA fragments so cannot measure gene expression.
Quantitative Polymerase Chain Reaction (qPCR) reveals a relative quantification of DNA content of a specific sequence but does not reveal gene expression.
Quantitative Reverse Transcriptase Polymerase Chain Reaction (qRT-PCR) is a quantitative method for measuring relative transcript levels of genes using reverse transcription and qPCR.
After 48 hours of starvation, which one of the following is the major source of glucose for the brain and erythrocyte?
a) ketone bodies
b) fatty acids
c) liver glycogen
d) muscle glycogen
e) muscle protein
e
The brain is only capable of using glucose or ketone bodies as respiratory fuel.
During prolonged starvation, the primary source of glucose is gluconeogenesis from amino acids arising from skeletal muscle protein breakdown. During starvation, most tissues utilise fatty acids and/or ketone bodies to spare glucose and thus spare muscle protein for the brain.
What is the function of high density lipoprotein?
a. it carries cholesterol from the liver to the large intestine for excretion
b. it carries triacylglycerols from the adipose tissue to the peripheral tissues
c. it carries cholesterol from the liver to the peripheral tissues
d. it carries cholesterol from peripheral tissues to the liver Correct
e. it carries triacylglycerols from the small intestine to the periphery
d
HDL originates from the liver. It removes the build up of cholesterol throughout the bloodstream and artery walls, then delivers them to the liver where they can be broken down. On the contrary, low density lipoprotein (LDL), also originating from the liver, carries cholesterol around the bloodstream often depositing itself into the artery walls creating plaque build up.
Microvilli, which function to increase surface area, are more likely to be found in ____________ epithelium.
a. Simple squamous
b. Simple cuboidal
c. Stratified columnar
d. Transitional
e. Simple columnar
e
A major difference between bone tissue and other connective tissues lies in which of the following?
a) the presence of elastic fibres in bone
b) the presence of collagen fibres in bone
c) the inability of bone cells to metabolise nutrients for energy
d) the limits blood supply available to bone tissue
e) the composition of the intercellular substance of bone
e
Bone is a specialised connective tissue consisting of cells, fibres and ground substance. Unlike other connective tissues, its extracellular components are mineralised giving it substantial strength and rigidity. This makes bone ideally suited to fulfilling its most recognised role within the body, that of mechanical support.
Which heart structure contains oxygenated blood?
a) right atrium
b) transverse sinus
c) coronary sinus
d) pulmonary artery
e) pulmonary vein
e
Which one of the following cell types is described as follows? ‘These cells circulate in the blood for 1-3 days, and then migrate into body tissues, where they transform into macrophages. They will phagocytose dead cells and bacteria and are important in the inflammatory response. These cells can also transform into osteoclasts.’
a. Monocyte
b. Lymphocyte
c. Eosinophil
d. Basophil
e. Neutrophil
a
Monocytes are the largest type of leukocyte (white blood cell) and can differentiate into macrophages, osteoclasts and myeloid lineage dendritic cells.
Which of the following features are unique to skeletal muscle?
a. cells are syncytial and multinucleate
b. cells appear striated due to organisation of contractile proteins
c. presence of intercalated discs
d. contraction is regulated by calcium reflux
e. associates with perimysium, epimysium and endomysium
a
Each myotube is formed by fusion of multiple stem cells in the developing organism or by fusion of satellite cells in the adult. This results in a. giant cell in which many nuclei share and common cytoplasm.
