ToB Flashcards
Define: Zygote
A fertilised oocyte
Define: Cleavage
The division of the zygote into two blastomeres
Define: Zona Pellucida
A glycoprotein shell around the zygote to protect it from polyspermy.
Define: Morula
A clump of cells as a result of division of the zygote. Each cell is totipotent. ~ 8 cells.
Define: Ampulla
A position inside the fallopian tube in which oocytes are normally fertilised.
Define: Uterus
Female reproductive organ where zygote normally implants and where embryo growth normally occurs.
Define: Blastocyst
Formed by the compaction of cells which make up the morula
Define: Trophoblast
The outer cell mass which later develops to be supportive tissue for the embryo.
Define: Embryoblast
The inner cell mass which later develops into the bilaminar disk.
Define: Implantation
The attachment of the blastocyst to the uterus wall.
Define: Cytotrophoblast
A derivative of the trophoblast - surrounds the bilaminar disk and yolk sac.
Define: Syncytiotrophoblast
A derivative of the trophoblast which invades the maternal sinusoids in order to establish uteroplacental circulation.
Describe the formation of a blastocyst.
In week 1, the cells which make up the morula are compacted in order to form the blastocyst. The blastocyst includes:
- Trophoblast
- Embryoblast
- Blastocyst cavity
Describe hatching and why is it important?
The blastocyst hatches from the zona pellucida.
This is important as it means that:
1. Blastocyst is not restricted from growing larger (can now enlarge)
2. Blastocyst can now interact with uterus for implantation.
What does the embryoblast differentiate into?
- Epiblast
2. Hypoblast
What does the trophoblast differentiate into?
- Cytotrophoblast
2. Syncytiotrophoblast
Name two conditions where implantation is defected. Where do they occur?
- Ectopic pregnancy - Implantation in fallopian tube
- Placenta praevia - Implantation in lower uterine segment
(grows across cervical opening).
Name the layers of the bilaminar disk
- Epiblast
2. Hypoblast
Name the two cavities produced in week 2
- Amneotic cavity
2. Yolk sac
What pushes the yolk sac away from the cytotrophoblast?
Acellular extraembryonic reticulum.
How is uteroplacental circulation established?
Syncytiotrophoblast invades the maternal sinusoids. Sinusoids and lacunae become continuous and circulation is established.
What does the extraembryonic reticulum develop into?
Extraembryonic mesoderm
What does the extraembryonic mesoderm develop into? How?
Spaces in the extraembryonic mesoderm join to form the chorionic cavity. This occurs at the end of week 2.
What 5 features have been established by the end of week 2?
- Conceptus has implanted (uteroplacental circulation setup)
- Bilaminar disk is formed
- Two cavities formed (amneotic cavity and yolk sac)
- Connecting stalk is connected
- Supporting sac (chorionic cavity) is present.
Define: Fertilisation
When a sperm cell enters an oocyte to produce a zygote.
Define: Bilaminar disc
Epiblast and hypoblast form the bilaminar disc. Following gastrulation, this will become the trilaminar disc.
Define: Ectoderm
The outer most layer giving rise to the epidermis and nervous system
Define: Mesoderm
The middle germ layer giving rise to muscles, blood vessels
Define: Endoderm
The inner most germ layer which gives rise to the epithelia of the GI tract.
Define: Primitive streak
A narrow groove which runs on the dorsal side of the bilaminar disc and has the role of determining the front and back of the embryo.
Define: Trilaminar disc
Three germ layers which include ectoderm, mesoderm and endoderm.
What three cavities are present in week three?
- Amniotic cavity
- Yolk sac
- Chorionic cavity
What are the two ways cellular rearrangement can occur in gastrulation?
- Migration
2. Invagination
What is another word for anterior in an embryo?
Cephalic
Another word for posterior in an embryo?
Cadaul
Where is the primitive node?
At the cephalic end of the primitive streak
What happens to the primitive streak as the trilaminar disc develops more?
It regresses.
In cellular rearrangement in gastrulation, where do the epiblasts migrate to?
Towards the primitive streak and then invaginate in epiblast in order to displace the hypoblast.
What are the two points which are not covered with mesoderm when the trilaminar disc is forming?
- Future mouth
2. Future anus.
Give 4 roles of the notochord.
- Basis for the axial skeleton
- Drives neurulation (nervous system development)
- Defines the midline
- Define phylum Chordata
How is left-right development controlled?
Ciliated cells on the node beat in a signalled direction.
Define: Dorsal
The back of an embryo
Define: Ventral
The front of an embryo
Define: Cephalic
Anterior/head of an embryo
Define: Caudal
Base/posterior of an embryo
Name two fixatives for microscopy
Glutaraldehyde and Formaldehyde
Define: Tissue
A collection of cells specialised for a specific function.
What do aggregations of tissues form?
Organs
Give 6 biopsy techniques, how they are done and give an example of tissues they are used on.
Smear - Wipe to get loose sample - eg. Cervix
Curettage - Scrape/scoop some tissue - eg. Uterus
Needle - Needle to get cylinder of tissue - eg. Liver
Direct Incision - Direct cut of tissue - eg. Skin
Endoscopic - Endoscope + scissors to make cut - eg. Lung
Transvascular - Cut using scissors - eg. Heart
How do we get stained slices of a sample from a wet biopsy?
Water –> Ethanol –> Xylene/Toluene –> Wax
Slice.
Most stains are water soluble
Wax –> Xylene/Toluene –> Ethanol –> Water
Stain.
Creating stained slices involves hydration and dehydration. What can this cause?
Can cause shrinkage artefacts.
Name 2 staining techniques - list the what they stain and the colours they show.
- Haemotoxylin and Eosin:
Haemotoxylin - acidic components are stained purple/blue
Eosin - basic components are stained pink - Periodic Acid-Schiff:
Stains carbohydrates and glycoproteins magenta.
What is Phase contrast microscopy? Advantages?
Exploits the interference pattern produced by two beams of light. Advantage is that it enhances image of unstained cell.
What is Dark Field microscopy? Advantage?
Excludes unscattered light from the image. Can be used on live and unstained samples.
What is Fluorescence microscopy? Advantage?
Can be made so target molecules are stained with fluorescence. Advantage is that multiple fluorescent stains can be used on the same sample.
What is confocal microscopy? Advantage?
Tissue labelled with one or more fluorescent probe. Removes the ‘out-of-focus’ glare and can be used to make 3D image from multiple 2D images.
Give an example of ectoderm
Epidermis of skin.
Give an example of mesoderm
Blood vessels
Give an example of endoderm
Epithelium of the GI tract
In terms of epithelia, what does simple mean?
One cell layer thick.
In terms of epithelia, what does stratified mean?
More than one cell layer thick.
Give 2 examples of simple squamous epithelia and give their functions.
- Lining of blood vessels - Gas exchange (thin)
2. Pericardium - Lubrication
Give an example of simple cuboidal epithelium and give its function.
Kidney tubule - Absorption and secretion
Give an example of simple columnar epithelium and give its function.
Stomach lining - secretion
Give an example of ciliated simple columnar epithelium and give its function.
Small intestine - absorption
Give an example of pseudostratified epithelium and give its function.
Trachea - Secretion (eg. mucus)
What is the Zonula Occluden?
The association between two close cells, making the gap impermeable to fluid.
Give an example of Stratified Non-keratinised squamous epithelium and give its function
Oral cavity - protection from abrasion.
Give an example of stratified keratinised squamous epithelium and give its function.
Skin - protection from abrasion and protection from UV light.
Give an example of stratified columnar epithelium and give its function.
In the male urethra - secretion and protection.
Give an example of transitional epithelium and give its role.
Bladder - Distensibility
Name the three types of surface modifications found on epithelia. Location? Function?
Microvilli - Increase surface area - small intestine
Stereocilia - Long microvilli, increase absorption - epididymal
Cilia - Beat in coordinated waves - trachea (mucus)- 9+2 shape
Define: Gland
An epithelial cell or a collection of cells which are specialised for the role of secretion.
Define: Exocrine
A gland with ducts.
Define: Endocrine
A ductless gland which secretes directly into the bloodstream.
Name the two shapes which glands may be
Tubular or acinar
What are the two types of glands present in the body?
- Serous gland
- Mucous gland
Name three methods of secretion
- Merocrine
- Apocrine
- Holocrine
Define: Merocrine secretion
Exocytosis. Where a vesicle binds to a plasma membrane and releases its contents into the extracellular space.
Define: Apocrine secretion
This is where the non-membrane bound structure pushes up against the cell membrane, causing a vesicle to form around it.
Define: Holocrine secretion
This is secretion where disintegration of the cell releases the contents.
Define: Endocytosis
The opposite of exocytosis. Structure which are originally outside of the the cell are engulfed into the cell.
Name 4 functions of the golgi apparatus
- Sorting into different components
- Glycosylation (O-linked)
- Packaging (through condensation of contents)
- Secretion/export
Name the three destinations of exports from the golgi apparatus
- Secretory vesicles
- Use in the cell (lysosomes)
- Enter plasma membrane (glycocalyx)
Does glycosylation make molecules more or less specific?
More specific
eg. Branching sugars cause specific interactions in the glycocalyx.
Name the four mechanisms of control of secretion
- Nervous control
- Endocrine control
- Neuro-endocrine control
- Negative feedback chemical control
Give an example of an endocrine gland
Thyroid gland
Give an example of an exocrine gland
Goblet cells
Is the pancreas:
endocrine, exocrine or both?
Both.
Where are mucous membranes found?
Line tubes open to the exterior.
Where are serous membranes found?
Lining tubes not open to the exterior.
What do serous membranes secrete?
A watery, lubricating fluid.
What do mucous membranes secrete?
Mucus.
Describe the structure of the gut wall
Mucosa - Epithelium - Lamina propria - Muscularis Mucosa Submucosa Muscularis Externa Serosa
Describe the structure of the Oesophagus
Mucosa - Epithelium - Lamina propria - Muscularis mucosa Submucosa Muscularis externa Adventitia
Describe the structure of the stomach
Gastric mucosa - Epithelium - Lamina propria - Muscularis mucosa Submucosa Muscularis externa Rugae
Describe the structure of the jejenum
Jejunal Mucosa - Epithelium - Lamina propria - Muscularis mucosa Submucosa Muscularis externa Plicae circulares
Describe the structure of the large intestine
Mucosa - Epithelium - Lamina propria - Muscularis mucosa Submucosa Muscularis externa
Describe the structure of the trachea
Mucosa - Epithelium - Lamina propria Submucosa Hyaline C shaped cartilage Adventitia
Describe the structure of the bronchus
Mucosa -Epithelium - Lamina propria Smooth muscle Submucosa Crescent shaped caritilage
Describe the structure of the bronchiole
Mucosa -Epithelium - Lamina propria Smooth muscle Alveoli
Describe the structure of the alveoli
Epithelium
Describe the structure of the ureter
Mucosa - Epithelium - Lamina propria Muscularis Externa Adventitia
Describe the structure of the bladder wall
Mucosa - Epithelium - Lamina propria Smooth muscle Muscularis Externa
Describe the structure of the urethra
Mucosa - Epithelium - Lamina propria Muscularis Externa Adventitia
Define: Limit of Resolution
The minimum distance two objects can be distinguished at
Why are electron microscopes able to have a finer resolution than optical microscopes?
Resolution is proportional to the size of the wavelength. Electrons have a much smaller wavelength than light.
Define: Amphipathic
A molecule which has a hydrophillic region as well as a hydrophobic region.
True or False:
The glycocalyx is a cell coat formed by oligosaccharides on the plasma membrane. It offers specificity to the cell.
True.
Give two functions of the plasma membrane.
- Cell morphology and movement
2. Transport of small molecules along cell surface
Give the two main functions of the nucleus.
- Store the cell’s DNA
2. Coordinate the cell’s activities.
Give a function of a ribosome?
- Site of translation (protein synthesis)
Give 2 functions of endoplasmic reticulum.
- Addition of N-linked polysaccharides to proteins
2. Export of proteins
In respect to frequency of secretion, give the two types of secretion.
- Constitutively
2. Regulated
Name the two faces on the Golgi apparatus.
- Cis face
2. Trans face
Name 4 functions of the golgi apparatus.
- Sort
- Modify
- Package
- Transport
True or false:
Lysosome inner surface is glycosylated to protect it from damage by enzymes inside it.
True
Give a function of perioxisomes.
- Detoxification reactions - produce H2O2 which can be used to oxidise substances (eg. alcohol).
Give the main function of mitochondria.
- ATP synthesis.
Describe the structure of mitochondria.
Double layer membrane where the inner membrane is folded in such a way to form cristae (which increase the surface area for reactions). The space formed within the cristae is called the matrix.
Name the three structures found within the cytoskeleton.
- Microfilaments (forms a mesh)
- Intermediate filaments (forms a mesh)
- Microtubules (found at moving parts - eg. flagellum)
Define: An Infection
The multiplication of a pathogen in/on a susceptible host with associated damage.
Name 3 factors which may make an individual more susceptible to infection.
- Age (very young or old)
- General lifestyle
- Weakened immune system (HIV?)
What determines the outcome of an infection?
The immune response of the individual, the affected body systems and the drugs used.
Describe the cell walls in eukaryotes, bacteria and viruses.
Eukaryotes = No cell wall Bacteria = Peptidoglycan or lipopolysaccharide cell wall Viruses = No cell wall
Describe the position of organelles (eg. membrane bound) in eukaryotes, bacteria and viruses.
Eukaryotes = Membrane bound organelles Bacteria = Not membrane bound organelles Viruses = No organelles
Describe the nucleus in eukaryotes, bacteria and viruses.
Eukaryotes = Nucleus with DNA inside Bacteria = No nucleus - circular diffused DNA Viruses = No nucleus
Describe the presence of DNA and RNA in eukaryotes, bacteria and viruses.
Eukaryotes = DNA and RNA Bacteria = DNA and RNA Viruses = DNA or RNA
Describe the presence of flagellum or pili in eukaryotes, bacteria and viruses.
Eukaryotes = No flagellum or pili Bacteria = May have flagellum or pili Viruses = No flagellum or pili
True or false:
We can classify bacteria using the gram stain technique.
True
With the gram stain technique, what colour does gram positive and gram negative bacteria stain?
Gram positive = Blue
Gram negative = Red
True or False:
Acid Fast stain allows you to classify bacteria not seen with the gram stain method.
True
Define: Pathogen
A microorganism that can cause disease.
Give an example of a DNA enveloped virus
Hepatitis B
Give an example of a DNA non-enveloped virus
HPV
Give an example of a RNA enveloped virus
HIV
Give an example of a RNA non-enveloped virus
Polio
Define: Reservoir
Any person, animal, plant, soil or substance that can allow an infectious agent to live/multiply.
Define: Source of infection
A readily available form of an infectious agent.
Give 3 types of transmission of an infectious agent.
- Inhalation
- Ingestion
- Sexual
Give the three growth mechanism for bacteria
- Broth
- Colony
- Biofilm
Describe the shape of staphylococci bacteria
Small circular bacteria in clusters
Describe the shape of Bacilli/Rod bacteria
Rod shaped bacteria
Describe the shape of Streptococci bacteria
Small circles connected in a chain (like a caterpillar)
Describe the shape of Diplococci
Two shapes connected together (in pairs)
Give the main function of fibroblasts.
To synthesise and maintain extracellular matrix.
Give the main function of macrophages
To ingest foreign material
Give the main function of Mast cells
Located near blood vessels, they release histamine and heparin into the blood when there is a foreign pathogen - causes swelling/inflammation.
Give two functions of adipose tissue
- Storage of energy
2. Shock absorber
Give the main function of leukocytes
Responsible for producing immunocompetent cells
Give 3 different types of fibre
- Collagen
- Reticular
- Elastic
Give two substances the amorphous ground substance is made up of.
- Hyaluronic Acid
2. Glycosaminoglycans
What is loose connective tissue? Give an example.
This is connective tissue where fibres are spaced out and there is a high proportion of ground substance. An example is areolar connective tissue.
What is dense regular connective tissue? Give an example.
Fibres organised in parallel for strength with little ground substance between fibres. Eg. Tendons.
What is dense irregular connective tissue? Give an example.
This is where fibres are close together with little ground substance between, but are organised in different directions. Eg. the dermis (prevents tearing).
What are keloids?
Formations of scars on the skin due to too much collagen
What is Marfan’s syndrome?
Genetic defect which means that the fibrillin protein is not correctly coded for. Fibrillin change affects elastic fibres.
What are chondroblasts? How do they become chondrocytes?
Chondroblasts are cells which release matrix around themselves in order to form cartilage. Once they become surrounded and part of the structure, they are called chondrocytes.
Give one place where hyaline cartilage may be found
Respiratory passageways
Give one place where elastic cartilage may be found
Epiglottis
Give one place where fibrocartilage may be found
Intervertebral discs.
True or False:
Hyaline cartilage and elastic cartilage both calcify with age.
False.
Hyaline cartilage does. Elastic cartilage does not.
Name the two types of bone in the body
- Cancellous bone (spongy)
2. Compact bone
What fills the gaps in cancellous bone?
Bone marrow.
Define: Haemopoiesis
This is the production of blood cells and platelets - occurs in bone marrow
What are osteoclasts?
These are macrophages found in bone which have the function of breaking down old/damaged bone.
What is the primary microstructure of bone?
Interwoven fashion of collagen fibres - immature bone.
What is the secondary microstructure of bone?
Compact bone is formed - consentric lamellae surround Haversian canals. Haversian canals link via Volkmann’s canals.
What are interstitial lamellae?
These are non-complete rings of concentric lamellae.
What are the five steps of a bone break from break to repaired?
- Break
- Haematoma
- Cartillage callus
- Primary microstructure bone
- Secondary microstructure bone
Name 5 variations in macroscopic structure of the skin.
- Colour
- Hair
- Thickness
- Laxity/wrinkles
- Oiliness
Vitiligo is the depigmentation of the skin. Is it more of a problem in dark or light skinned people?
More of a problem in dark skinned people as it is more visible.
Name the 4 regions of the epidermis.
- Stratum corneum
- Granular layer
- Prickle cell layer
- Basal layer
How is new skin produced?
Keratinocyte mitosis occurs at the basal layer and moves up to the prickle cell layer. Here, keratinocytes can no longer replicate but can produce keratin. Then as the keratinocyte progresses further up, into the granular layer, major changes occur. Keratinocyte becomes corneocyte, forming the stratum corneum.
How long does it take for a keratinocyte at the basal membrane to become a corneocyte? (Transit time)
30-40 days.
What is the shape of fibroblasts?
Spindle shaped
Name 4 skin appendages.
- Sebaceous gland + Hair follicle (pilosebaceous unit)
- Eccrine/Apocrine sweat gland
- Nails
- Immediate subcutaneous fat
Name 4 main functions of skin.
- Barrier protection
- Sensation
- Thermoregulation
- Psychosexual communication
What is psoriasis?
Excessive production of stratum corneum which results in scaling.
What is vitiligo?
This is depigmentation of the skin - melanocytes have been damaged by the immune system.
What is Alopecia Areato?
This is hair loss due to the immune system damaging hair follicles.
What is malignant melanoma?
This is skin cancer.
Average size of a Human body cell?
10-20um
Average size of a Red Blood Cell?
7.2 um
Most common type of collagen found in basal lamina?
Type IV
Define: Myoepithelial Cells
Cells found in glands, located between the basal lamina and luminar cells - these myoepithelial cells cause contraction of the gland in order to secrete the contents.
How do drugs which target cell walls (eg. Penicillin) work against bacteria?
Enzymes which form cross links in cell wall are inhibited. Osmotic pressure causes cell lysis.
How do drugs which target bacterial transcription (eg. Rifampicin) work?
Binds to RNA polymerase, preventing transcription.
How do drugs which target bacterial protein synthesis (eg. Tetracycline) work?
Bind to A site of rRNA meaning that aminoacyl-tRNA cannot bind.
How do anti-folates (such as methotrexate) work?
Impairs synthesis of tetrahydrofolate which is essential for DNA synthesis from folic acid.
Describe the 4 types of collagen.
Type 1 = Most common type; forms fibres - eg. dermis +
tendons
Type 2 = No fibres. eg. Elastic and hyaline cartilage
Type 3 = Fibres around muscles, nerves + lymphatic
tissue. Called Reticulin.
Type 4 = Uniquely found in basal lamina.
What do langerhans cells do in the epidermis?
Present microorganism’s antigens on its surface and induces an immune response.
What do melanocytes do in the epidermis?
Melanocytes are mostly found in the basal layer. They produce melanin which gives skin it’s colour. Those with darker skin have MORE melanin but the SAME amount of melanocytes.
Where is the dermo-epidermal junction found? What is significant about it’s shape?
Located below the basal layer of the epidermis and above the dermis. It is the junction between the two. Has a wavy shape which causes layers to interlock, preventing them from sliding off from each other.
Which causes smelling sweat? Eccrine or apocrine?
Eccrine produces non-smelling sweat which helps with thermoregulation whilst apocrine produces sweat which serves no function. Apocrine sweat is then digested by microbes which produces a smell.
Where does cartilage originate from?
Mesenchyme
How do chondrocytes form?
Chondroblasts are derived from mesenchyme and then begins to lay down matrix around itself. When it is surrounded fully, it is now a chondrocyte.
True or false:
Embryo skeleton is originally Hyaline cartilage.
True. It begins as hyaline cartilage which is then converted into bone. Any remaining hyaline cartilage becomes the epiphyseal growth plate or the articular surfaces.
Give the 3 types of cartilage.
- Hyaline cartilage
- Elastic cartilage
- Fibrocartilage
Out of Hyaline, elastic and fibro- cartilage:
Which cartilage(s) have a perichondrium?
Hyaline and elastic.
Out of Hyaline, elastic and fibro- cartilage:
Which cartilage(s) offer structural very strong support?
Fibrocartilage
Give 2 examples of hyaline cartilage.
- Embryo skeleton
2. Respiratory passageways (eg. trachea)
Give 2 examples of elastic cartilage.
- Ears
2. Eustachian tube
Give 2 examples of fibrocartilage.
- Inter-vertebral discs
2. Meniscus (eg. of the knee)
Describe the structure of compact bone.
Circular lamellae which surround Haversian canals with Volkmann’s canals inter-connecting them. Haversian and Volkmann’s canals carry blood vessels, nerves and lymphatic vessels.
Describe the structure of cancellous bone.
Trabeculae which form a network in bone. The gaps in between the trabeculae is filled with bone marrow.
What do osteogenitor cells become?
Osteoblasts.
What do osteocytes do?
Maintain bone.
What do osteoclasts do?
Break down bone to release calcium.
What do osteoblasts do?
Release osteoid matrix which is mineralised to then form bone.
What is the main component of bone?
Hydroxyapatite crystals.
Which hormone upregulates osteoclast activity and which lowers it?
Parathyroid hormone - increases
Calcitonin - decreases
Difference between primary and secondary bone?
Primary bone is immature, irregular and woven bone. Secondary bone is compact and cancellous bone.
What is endochondral ossification?
This is growth of a bone from its diaphysis (primary ossification site) or from its epiphyseal growth plate. This growth is replacing cartilage for bone.
What is intramembranous ossification?
This is loose connective tissue/mesenchyme which is becomes bone.
5 stages of a bone break?
- Bone breaks
- Haematoma
- Fibrocartilaginous callus formation
- Primary bone formation
- Secondary bone formation
5 zones of epiphyseal growth plate?
- Zone of reserve cartilage
- Zone of proliferation
- Zone of hypertrophy
- Zone of calcified cartilage
- Zone of ossification.
What is osteo imperfecta?
Rare hereditary disease where bones are more fragile due to abnormal collagen synthesis by fibroblasts and osteoblasts. Can result in multiple fractures which may appear to be deliberate.
What is rickets?
Due to a calcium deficiency in children, epiphyseal growth is distorted and bones become distorted + slow growing. The bones are not calcified correctly.
What is osteomalacia?
Due to a calcium deficiency in adults, bones become more fragile.
Difference between rickets and osteomalacia?
Rickets occurs in children whilst osteomalacia is in adults. Not only this, but rickets affects growing bones whilst osteomalacia affects remodelling bones.
What is osteoporosis?
Generally in older people (particularly women), osteoclast activity is greater than osteoblast activity meaning that bone density reduces making bones more fragile.
Give 3 risk factors of osteoporosis
- Middle aged women following the menopause (less oestrogen)
- Insufficient exericise
- Smoking
What is achondroplasia?
This is a congenital and hereditary condition where the epiphyseal growth plate does not function correctly. The growth plate is thin, has few cells in the proliferation zone and the hypertrophy zone cannot form columns like it normally should.
What is wrong with an excess or lack of growth hormone?
Excess: If there is an epiphyseal growth plate, then this can cause giantism. If there is no growth plate (in an adult), this can cause acromegaly as long bones do not lengthen but bones just thicken.
Lack: Can cause pituitary dwarfism.
What is wrong with excess or lack of sex hormones?
Premature/excess: Epiphyseal growth plate closes early so stunted body growth.
Lack: Can cause epiphyseal growth plate to close later giving a tall stature.
What do we call weeks 1-2 of pregnancy?
Pre-embryonic period
What do we call weeks 3-8 of pregnancy?
Embryonic period
What do we call weeks 9-38 of pregnancy?
Foetal period
Describe the location of the primitive streak.
Dorsal side of the epiblast.
What does the regressed notochord become?
Becomes the nucleus pulpous which lies between inter-vertebral discs.
Define: Germ layer
A layer from which tissue is derived from.
Give 3 examples of derivations from the ectoderm.
- Epidermis (skin)
- Brain + spinal cord
- Retina of the eye
Give 3 examples of derivations from the mesoderm.
- Blood vessels
- Bones
- Muscles
Give 3 examples of derivations from the endoderm.
- GI tract
- Respiratory tract
- Thyroid + parathyroid
Define: Gastrulation
The process which is marked by the formation of the primitive streak. In the process, bilaminar disc becomes the three germ layers.
Describe the layers in a peripheral nerve.
Nerve fibres are surrounded by endoneurium; these then clump together to form fascicles. Fascicles are surrounded by perineurium. These fascicles along with blood vessels form the peripheral nerve which is surrounded by epineurium.
Which is myelinated - white or grey matter?
White matter
Describe how myelination makes faster impulses.
A myelin sheath cannot conduct impulses as no action potentials can form. The myelin sheath is not continuous and the small gaps are called the nodes of ranvier. Action potentials can form in these gaps only so the impulse jumps between nodes. This is called saltatory conduction.
Which cell type causes myelination in the CNS?
Oligodendrocytes
Which cell type causes myelination in the PNS?
Schwann Cells
Give 2 excitatory neurotransmitters.
- Acetylcholine
2. Glutamate
Give 2 inhibitatory neurotransmitters.
- Glycine
2. GABA
What happens in multiple sclerosis?
Demyelination occurs and the myelin sheath is replaced with scar tissue instead. Without the sheath, saltatory conduction cannot occur. Also, as scar tissue cannot conduct an action potential, the axon becomes useless.
Where is the nucleus normally located in a cell body? When can it move?
The nucleus is normally centrally located in a cell body. However it can become off-centre if injury has occurred.
How many axons can a schwann cell myelinate?
1 at a time.
How many axons can an oligodendrocyte myelinate?
Around 250 at a time.
Describe the glial cells in the CNS. Give functions.
- Microglial cells - Provide immunity and give an inflammatory function.
- Astrocytes - Constitute the blood-brain barrier as well as transferring waste products from the brain to the blood. Gives physical support to CNS neurones.
- Oligodendrocytes - Can myelinate up to 250 axons at a time.
- Ependyma - Line spinal cord canals to allow cerebrospinal fluid (CSF).
Describe the glial cells in the PNS. Give functions.
- Microglial cells - Provide immunity and give an inflammatory function.
- Schwann cells - Can myelinate up to 1 cell at a time.
- Satellite cells - Give physical support to PNS neurones.
Define: Ganglion
Collection of cell bodies
Which part of the spine outflow is for the sympathetic?
Thoraco-lumbar outflow
Which part of the spine outflow is for the parasympathetic?
Cranio-sacral outflow
Describe the lengths of the pre and post ganglionic nerve fibres in the sympathetic nervous system.
Pre-ganglionic nerve fibre = Short
Post-ganglionic nerve fibre = Long
Give the 3 methods of termination which can occur in the sympathetic nervous system.
- Can terminate at the same level as the origin
- Can terminate above/below the level of the origin – then travels up or down the sympathetic chain.
- May not synapse at all at the sympathetic chain.
Describe the lengths of the pre and post ganglionic nerve fibres in the parasympathetic nervous system.
Pre-ganglionic nerve fibres = Long
Post-ganglionic nerve fibres = Short
What effects does the sympathetic nervous system have? Give 5.
- Fight or flight
- Increased blood flow to heart + muscles
- Vasoconstriction to skin + GI tract
- Increased respiration rate
- Ejaculation in men (S= Shoot)
What effects does the parasympathetic nervous system have? Give 5.
- Rest and digest
- Promotes digestion
- Reduces heart rate.
- Promotes sleep
- Erection in men (P= Point)
For the sympathetic nervous system, describe:
- Pre-ganglionic neurone type
- Post-ganglionic neurone receptor type
- Post-ganglionic neurone type
- Effector organ receptors
- Cholinergic (acetylcholine)
- Nictonic receptors
- Noradrenergic
- Alpha + Beta receptors
For the parasympathetic nervous system, describe:
- Pre-ganglionic neurone type
- Post-ganglionic receptor type
- Post-ganglionic type
- Effector organ receptors
- Cholinergic (acetylcholine)
- Nictonic receptors
- Cholinergic (acetylcholine)
- Muscarinic receptors
Give the 3 types of muscle
- Skeletal muscle
- Smooth muscle
- Cardiac muscle
What does MHAZI stand for?
Positioning of features in skeletal muscle.
M line is in the H band which is in the A band. Z line is in the I band.
What makes up the light band?
The I band is formed from actin.
What makes up the dark band?
The A band is formed from actin and myosin overlapping
Which is thicker: Actin or Myosin?
Myosin is thicker than actin.
Describe how muscles contract using the actin-filament mechanism.
Ca2+ binds to the TnC of troponin which causes a conformational change so that tropomyosin moves to expose the binding sites on the actin filament.
Myosin heads form cross bridges to the actin filament and a working stroke pulls the actin filament over the myosin filament. ADP and Pi are released. Then, ATP binds causing the cross bridges to break. ATP is then hydrolysed and the energy from this causes the myosin head to cock back into it’s original position.
Describe innervation causing muscle contraction.
An action potential arrives at a presynaptic knob and causes Ca2+ ions to move from the extracellular fluid into the presynaptic knob. This causes secretory vesicles to move and fuse with the presynaptic knob and release acetylcholine into the synapatic cleft.
The acetylcholine binds to acetylcholine receptors on the post-synaptic membrane and causes Na+ and K+ channels to open. K+ moves out of the membrane whilst Na+ moves in; causing depolarisation in the post-synaptic membrane and allowing an action potential to be formed.
Acetylcholinesterase then travels to break up acetylcholine to stop the receptors being activated. The depolarisation travels into the sarcolemma and down T-tubules where they depolarise sarcoplasmic reticulum, causing Ca2+ ions to be released which then bind to TnC on troponin.
Explain the structure of skeletal muscle.
Actin and myosin make up myofilaments which join to form myofibrils. These myofibrils form muscle fibres which are surrounded by endomysium. Muscle fibres clump to form fasicles which are surrounded by perimysium. Fasicles and blood vessels join to form muscle which is surrounded by epimysium.
Describe how tendons and muscle join.
Tendons and muscles join at the myotendinous junction. A sarcolemma always lies between the two structures. Tendons join muscles to bone.
How is repair possible in mature skeletal muscle.
Cannot divide itself however satellite cells can divide to regenerate damaged muscle. Not only this, but satellite cells can fuse with the muscle to increase muscle mass.
How is repair possible in mature cardiac muscle.
Repair cannot occur as cardiac muscle has no mitotic activity. Instead, fibroblasts produce scar tissue.
How is repair possible in mature smooth muscle.
Smooth muscle maintains its ability to divide so can conduct mitosis to replicate itself to form new smooth muscle.
Describe the histology of skeletal muscle
- Striated
- Multiple nuclei which are peripheral
- Non-branching
- T-tubules are in line with A-I band junction
Describe the histology of cardiac muscle
- Striated
- 1 or 2 nuclei centrally located
- Branching
- T-tubules are in line with the Z line
- Intercalated discs for mechanical and electrical coupling
Describe the histology of smooth muscle
- Non-striated
- Spindle shaped cells with central nucleus
- Capable of being stretched
- Slow contraction but uses less ATP
- Forms sheets and layers
- Thin and thick bands are laid diagonally so muscle contraction is in a twisting fashion.
Explain the function of purkinje fibres and their structure
Fibres which pass from the atrioventricular node to the ventricles. Have large glycogen stores, sparse myofilaments and large gap junctions so electrical impulses are carried quickly. This allows synchronous contraction of the ventricles from the base upwards.
What is the term when:
Muscle destruction > Muscle replacement
Atrophy
What is the term when:
Muscle destruction
Hypertrophy
Give the 3 ways in which atrophy of muscles can occur.
- Disuse atrophy - Bed rest
- Age atrophy - As you get older
- Denervation - Lack of nerve connection
Give a way of causing hypertrophy
High intensity, high resistance exercise - muscle builds over time.
Explain Myasthenia Gravis
This is an autoimmune condition where acetylcholine receptors are damaged as well as synaptic clefts widening and junctional folds being lost. This causes less muscle contraction. Symptoms include fatigue, sudden falling, drooping eye lids, double vision.
Give a treatment of Myasthenia Gravis
Acetylcholinesterase inhibitor (gives more time for acetylcholine to bind to remaining receptors)
Explain Malignant Hyperthermia
A medical emergency when individuals are given an anaesthetic. In some people, large amounts of calcium are released from the sarcoplasmic reticulum. This causes heat generation and hyperthermia.
Describe Botulism poisoning
Toxins block acetylcholine release - causes a person to not be able to contract muscles
Describe Organophosphate poisoning.
Causes permanent inhibition of acetylcholinesterase so muscles are permanently contracted.
What happens in Duchenne Muscular Dystrophy?
Dystrophin protein which anchors actin to sarcolemma is completely absent so muscles tear when they contract. This causes creatine phosphate to be released into the blood serum and calcium enters muscles causing necrosis. Also, pseudohypertrophy occurs as muscles swell before muscle fibres are replaced by fat and connective tissue. Symptoms include early onset, pain and contractures (imbalance between agonistic and antagonistic muscles - shortening of muscles).
In which process is the notochord formed?
Gastrulation
Name the divisions of the mesoderm.
- Paraxial mesoderm is around the notochord
- Intermembrane mesoderm
- Lateral plate = somatic + splanchnic mesoderm
What does the paraxial membrane segment into?
31 somites which later become 31 spinal nerves
Describe the formation of the coelom
The space between the somatic mesoderm and the splanchnic mesoderm is called the intraembryonic coelom. When folding occurs, this joins to form the coelom.
What does the paraxial mesoderm eventually differentiate into?
- Vertebrae (sclerotome)
- Ribs
- Dermis (Dermatome)
- Some limb muscles (myotome)
What does the intermediate mesoderm eventually differentiate into?
Urogenital system
What does the somatic mesoderm eventually differentiate into?
- Connective body tissue
- Contributes to the axial body wall
What does the splanchnic mesoderm eventually differentiate into?
Connective tissue of the gut
Describe the formation of the neural tube
The notochord causes the ectoderm overlying it to become neuroectoderm. This causes it to thicken and form a key hole-shaped neural plate. The edges of this thicken and begin to curl together to form the neural tube.
Which two planes is embryo folding seen in?
Saggital (see tube on the side) or transverse.
Give 3 outcomes of cephalocaudal folding.
- Embryo is suspended in amniotic fluid
- 3D structure is present
- Ventral body wall is formed
What do somites organise into?
- Sclerotome (become vertebrae)
- Dermomyotome (dermatome = dermis + myotome = muscle)
What does dermatome mean regarding innervation?
A strip of skin supplied by a single spinal nerve.
What does myotome mean regarding innervation?
A single or group of muscle supplied by a single spinal nerve.
How does mytotome spread from dermomyotome?
It proliferates.
How does dermatome spread from dermomyotome?
It disperses.
Where do the nerves which innervate the dermomyotome originate from?
The neural tube.
Define: Innate immunity
This is immunity which an individual is born with. It is natural and native. It is not enhanced by second exposure and has no memory.
Give 2 examples of innate humeral immunity.
- Interferon (Inhibits viral replications + activates other cells which kill pathogens)
- Complement - components and their products which cause damage to pathogens either directly or through the help of phagocytosis.
Give 5 examples of innate cellular immunity.
- Monocyte/Macrophage = Phagocytosis + present antigens of pathogen to lymphocytes.
- Neutrophil = Phagocytosis and anti-bacterial
- Eosinophil = Phagocytosis and gives allergic response
- Basophil + Mast cells = Gives allergic response
- Natural killer cells = Recognise + kill foreign cells
Define: Adaptive immunity
This is immunity which is not natural and must be learnt. It is acquired and is specific. A memory is present and the response is enhanced by second exposure.
Give 2 examples of adaptive humeral immunity.
- Cytokines - Promotes differentiation and proliferation of lymphocytes.
- Antibodies - Protect the host by binding to pathogen antigens. Can neutralise pathogen.
Give 2 examples of adaptive cellular immunity.
- T cells = T-Helper cells or Cytotoxic T lymphocytes.
2. B cells = Plasma cells or memory cells
What do T helper cells do?
Activate B cells and macrophages.
What do Cytotoxic T lymphocytes do?
Kill virus infected cells
What do plasma cells do?
Plasma cells produce specific immunoglobulin (antibodies) which target pathogen antigens.
What do memory cells do?
These remain in the blood and on second exposure they lead to a more rapid adaptive immunity response
Describe 5 main differences between innate and adaptive immunity. Consider when they begin, if they are enhanced, their memory, specificity and effectiveness.
- Innate is from birth whilst adaptive is learnt
- Innate is not enhanced by first exposure whilst adaptive is
- Innate has no memory whilst adaptive does.
- Innate is not specific whilst adaptive is.
- Innate is not effective without adaptive immunity whilst adaptive is not effective without innate immunity.
Define: Haemopoiesis
This is the production of erythrocytes and other blood cells.
Where are blood cells derived from?
Progenitor stem cells.
What two stages does haemopoiesis include? Explain what happens in both stages.
- Proliferation - Progenitor stem cell divides into two. One to replace the original and another for differentiation.
- Differentiation - Dependent on the cytokines present, the progenitor stem cell can become myeloid progenitor or lymphocyte progenitor.
Give 2 examples of cytokines for differentiation.
- Erythropoietin = Differentiate myeloid progenitor into erythrocyte.
- Thrombopoietin = Differentiate myeloid progenitor into megakaryocyte to produce platelets.
What is the chemical name for T helper cells?
CD4+
What is the chemical name for T suppressor cells (Cytotoxic T lymphocytes)
CD8+
Diameter of a RBC?
7.2um
Lifespan of a normal RBC?
120 days.
How do we get jaundice from RBC breakdown?
Catabolism of RBC produces bilirubin which in excess gives jaundice.
Give an example of stratified cuboidal epithelium
Parotid glands
Give an example of stratified cuboidal epithelium
Parotid glands
Define calor with respect to inflammation.
Heat
Define rubor with respect to inflammation.
Redness
Define dalor with respect to inflammation.
Pain
Define tumor with respect to inflammation.
Swelling
Name the two types of ossification.
- Intramembranous Ossification
2. Endochondral Ossification
Order of meninges? Moving inwards.
DAP
Dura mater
Arachnoid mater
Pia mater
What is interdigitation?
This is as seen in the skin where the epidermis and dermis are in folds together to prevent shearing/layers slipping.
Give the name of the junction between skeletal muscle and tendons.
Myotendinous junction
What always lies between the collagen bundles of tendons and skeletal muscle at the myotendinous junction?
Sarcolemma
Describe how Chondrocytes are formed.
Chondrogenic cells (narrow and spindle shaped) become Chondroblasts. Chondroblasts secrete extracellular matrix around them and once surrounded they become Chondrocytes (Chondrocytes are often surrounded by a lacuna).
What connects osteocytes?
Canaliculi
Arrangement of flagellum microtubules?
9+2 arrangement of microtubules
How is bilirubin excreted?
Kidneys - excreted as urobilinogen
Large intestine - stercobilin
Drug to treat malignant hyperthermia?
Dantrolene - muscle relaxant by stopping Ca2+ release
What is a change in epithelium called?
Metaplasia