Fundamentals of body structure Flashcards
What are the 6 body regions?
Head Neck Thorax Abdomen Pelvis Limbo's
What does superior mean?
Towards the head
What does inferior mean?
Towards the feet
What does medial mean?
Towards the centre
What does lateral mean ?
To the side / away from middle of The Body
What does proximal mean?
Nearer to the point of reference
What does distal mean?
Further away from the point of reference
What does superficial mean?
Closer to the surface/ more externally
What does deep mean?
Away from the surface further into the body
What does palmer mean?
Palm of hand
What does planter mean?
Sole of the foot
What is the median sagittal plane?
Middle line down the body
What is the para sagittal plane?
Any plane parallel to the median sagittal plane
What is the axial/ transverse plane?
Separates the upper and lower body (top and bottom)
What is the coronal plane
Separates front and back (anterior and posterior)
How does the number of chromosomes change during reproduction?
2 haploid cells with 23 chromosomes combine to form a zygote (diploid cells with 46)
Describe the sperm (structures)
Haploid cell
Head of the sperm is covered by an acrosome cap which contains enzymes for fertilisation
- middle piece provides energy for swimming
-tail - microiubeles for movement
Describe the ovum structure egg
Haploid cell - cytoplasm holds all organelles used for cell function
- zone pullicida - outer membrane of the cell
- corona radiata = outermost layer of cells
Sperm must penetrate both layers
What layers must the sperm penetrate to fertalise the egg
Corona radiata
Zone pellucida
Describe the process of fertilisation
Intercourse → sperm is in vagina
- Sperm penetrates the corona radiata
- Sperm makes contact with zona pellucida and binds to receptors - initiates acrosomal reaction
- Sperm penetrates zona pellucida by secreting enzymes that breakdown the layer
- Sperm makes contact with oocytes plasma membrane and fuses with oocyte
- Sperm releases its nucleus into oocyte cytoplasm
What is the cleavage of cells?
After fertilisation zygote initiates a rapid series of mitotic divisions
→ cleavage increases the number of cells but the size of the cell remains the same
→ occurs up to morulla stage which is 16 cells
What 3 processes happen during the first week of development?
Cleavage
Blastocyst formation
Initiating implantation
When can totipotency occur and what is it?
Cells ability to divide and produce all differentiated cells in an organism
- it is possible at 8 cell stage
When is toripotency lost?
At 16 cell stage (morulla) as differentiation of cells begins to occur
What happens at day 3 of pre implantation?
- 16 cell morulla is formed
- totipotency is lost
- differentiation starts
Describe the formation of the blastocyst at day 5
Compaction→ blastomeres (cells) flatten and form polarity with each other, reorganisation of cells
- outer blastomere cells (trophoblast) = become polarised, secrete fluid from apical aspect and have ability to form placenta
- inner cell mass = will form embryo
Cavitation → outer blastomere cells secrete fluid into centre blastocoele cavity
Blastocyst is the: inner cell mass, trophoblast, blastocoele all surrounded by zona pellucida
Describe structure of blastocyst
Inner cell mass
Trophoblast (outer cells)
Zone pellucida
Blastocoele
Describe process of implantation (hatching and adhesion)
Hatching → blastocyst hatches from zone pellucida as the trophoblast secretes proteases that digest zone pellucida
Adhesion → exposes the sticky outer cells of blastocyst which adhere to the endometrium
Implantation → blastocyst implants in the posterior wan of uterus and the endometrium grows around it to secure it
What is ectopic implantation?
When blastocyst implants in an abnormal size = life threatening as it may disrupt blood vessels
How do regions differ from systems?
- Regions are where things are in The Body
- Systems are where organs work together
What are the 4 different types of tissue?
Epithelial
Connective
Muscle
Nervous
What is epithelial tissue?
- cover body surfaces
- no blood vessels
- supported by underlining tissues (basement membrane)
- can form glands
What is connective tissue?
- underlie epithelial and support / surround other structures
Eg bone - metabolic support
-structural stability
What is muscle tissue?
Aggregations of contractile cells
Mediate movement
What are nervous tissues?
Gather, transmit and integrate info from internal/external environments
Mount responses
What happens during the second week of development?
- formation of layers in the blastocyst, everything splits into 2, start to form cavities, fully implanted
Bilaminar disc formation
Amniotic and yolk sacs
How is the bilaminar embryonic disc formed?
Inner cell mass →differentiates into epiblast and hypoblast which together form the bilaminar embryonic disc
What is the amniotic cavity?
Cavity between epiblast and the trophoblast
- forms lining of extra embryonic mesoderm
- surrounded by amnion (thin layer from epiblast)
What is the yolk sac and how is it formed?
Hypoblast sends epidermal cells to form the lining of the blastocyst cavity - thin layer, primary yolk sac
Hypoblast sends another layer of cells to change primary yolksac to secondary yolk sac
Inner layer = endoderm
Outer layer= extra embryonic mesoderm
After implantation what does the trophoblast differentiate into?
Cytorrophoblast layer
Synctiotrophoblast layer
What does the extra embryonic mesoderm do?
Forms a new cavity ( extra embryonic / chorionic cavity)
Lines inner surface of trophablast
Lines outer surface of amnion and yolk sac
What happens in the 3rd week of development?
Primitive streak formation
Gastrulations (tri laminar disc)
Neural plate formation
What happens in gastrulation?
Bilaminar → trilaminar
- embryo takes an oval disc shape
- forms indentation in the middle = primitive store
How is the primitive stream formed?
Accumulation of cells
What are the 3 germ layers?
Endoderm
Ectoderm
Mesoderm
Define variation.
No two living organisms are structurally or functionally identical
Define normal range.
Range in which values indicate a healthy population (variation)
Define anomaly
Deviated from the expected normal
Define ‘compatability with life’
Anomalies may not all affect normal life
What are congenital abnormalities?
Structural or functional anomalies that occur during intrauterine life
Can be identified at birth
Most at risk during week 3 to 8
What are teratogens?
Factors that cause malformation of an embryo
Name 4 common teratogens
Medications
Recreational drugs
Chemicals
Alcohol
What is amioscentesis?
Process of having cells from amniotic sac to check for congenital disorders
What is a CT scan computed tomography?
Uses X rays to produce sectional images and 3d reconstructions
- painless and non invasive
- slight risk of cancer
What is an X-ray?
Beam of X rays passes through patient, those that are not absorbed emerge and impact Ona detector.
Different tissues absorb x rays differently
What is an ultrasound?
Sound waves travelling through a median are partly reflected when they hit amedium of different consistency
→ suitable for fluid filled cavities
What is a doppe ultrasound?
When wave motion is radiated from a moving source there is a change in frequency of the wave.
- in is provides more information about blood flow.
What does ventral mean?
At the back (posterior)
What does dorsal mean?
At the front (anterior)
What are chordata?
Animals that have d backbone, have a notochord
Give a congenital disorder
- Anencephaly = brain has come away from surface
- hydrocephalus = swelling of the brain
- spina bifida= vertebrae hasn’t formed round correctly, hernication
What is the notochord?
Plays important role in induction of vertebral bodies together with neural tube
Failure can cause:
- vertebral column abnormalities
- spina bifida and scoliosis
What is neuralation?
Process that converts neural plate into → forms hollow neural tube and crest
- notochord is under neural tube
- somites are on either side of the neural tube for protection
Describe the process of neurulation.
- ectoderm forms primitive streak witha huge accumulation of its cells
2 primitive stream bends downwards → neural tube
3.Somites are paraxial (on either side of) notochord - Somites breakdown into 3 components
- Somites build body of vertebrae, part of notochord remains part of intervertebral disc
- Neural tubes send out nerves into developing muscles - movement
What 3 components do somites breakdown into?
Sclerotome → gives rise to bone
Myotome → gives to muscle
Dermatome → gives rise to skin and connective tissue
What does the function of an organ system depend on?
Integrated activity of its organs
What does the survival of an organism depend on?
Integrated activity of organ systems
What is cytology?
Study of the cell
What is in-vitro study?
Study of cells outside of The Body using a Petri dish and culture medium
→ reflects now cells are grown outside The Body
How are fixed cells studied?
Using a special fixative - chemical material to preserve the cells
Using a special stain to study microscopic features
What is histology?
Study of tissues
What are the 5 steps to study tissues?
Tissue collection and preparation Fixation Sectioning Staining Microscope
What does in vivo mean?
Reflects how cells were in the living tissue
What is tissue sampling /collection?
Taking small slices from different areas of an organ to determine if the organ is clear from disease or if disease is present.
What is fixation?
Samples are fixed with a chemical fixative to allow proper sections to be taken
- formaldehyde to preserve tissue
- boiling
What is sectioning?
Using a microtome machine to cut extremely thin sections of material
- sections are mounted onto glass for light microscopes
- section and mount depend on microscope
- sections are put into a warm water bath, fished out on a slide and arranged to dry in the oven
What is staining? Give 2 stains.
Stain a section to visualise it under a microscope
- hematoxylin = alkali, stains nuclei blue
- eosin= acidic, stains cytoplasm pink
How does the orientation of a section affect the microscopic image?
Longitudinal and transverse sections look different
Depends on level and plane of section
What is an issue with increasing magnification?
Decreases the resolution, less clear
Describe the use of a transmission e electron microscope
→ beams of electrons are transmitted through the structure
1. Fix tissue with a strong fixative (glutaraldenyde)
2. Sectioned very thinly
3. Stained with special stain
4- view under microscope
What is a scanning electron microscope?
Used to see surface of organelles
Higher magnification and better resolution
Tissue fixed with strong fixative
Describe 2 cell shapes
Round/spherical
Long/cylindrical
What is the morphology of an erythrocytes?
No nucleus / spherical
What are the 3 types of cell consistency, give examples?
Fluids → blood
Semi solid → adipose tissue (fat)
Solid → cartilage
What is histology?
How to recognise normal structures
What is pathology?
How to recognise abnormal structure
What are the 4 steps to detect abnormalities at tissue level?
Small slices of the body are:
- Fixed
- Sectioned
- Stained
- Microscope
Give examples of connective tissue.
Cartilage Bone Tendon Ligament Blood
Give examples of epithelium.
Liver
Kidney
Skin
Lung
Gives example of muscle tissue.
Heart
Skeletal muscles
Gut wall
Give examples of nervous tissue.
Brain Eye Ear Spinal cord Nerves
What is simple tissue?
Collection of similar cells
What is compound tissue?
Mixture of cell types and matrix
most of our tissues
What is the skin made of?
Epidermis -epithelium tissue
Dermis - connective tissue
What are parenchyma?
Functional cells within the organ
What are stroma?
Supportive cells
Inc. connective tissue, blood vessel, nerves
What are the 3 types of muscular tissue?
Skeletal - contraction of skeletal parts
Smooth - walls of internal organs and blood vessels
Cardiac - walls of heart.
What specialisations do secretory cells have?
Loads of er golgi and secretory vesicles
To process and package
What specialisations do absorptive cells have?
High conc of microvilli - increases sa
How are light microscopes used?
- focus light with a series of glass lenses
- to magnify smaller details
- can’t see a slide without using an appropriate stain
What structures does hematoxylin stain?
Negatively charged structures (nucleus) as it is a stain with a positive charge
What structure does eosin stain?
Positively charged structures (cytoplasm) as the stain is negatively charged
What 4 characteristics of the cell can be noticed using a microscope?
Size of cell
Snape of cell
Nuclear / cytoplasmic ratio
Chromatin condensation (heterochromatin and euchromatin)
What is heterochromatin?
Highly packed chromatin (dense) - nuclei stained darkly
Describe the arrangement of organs in the internal environment.
- Internal organs and body cavities are often covered in serous membrane from mesoderm = it secretes fluid that acts as a lubricant to reduce friction from muscle movement
- internal organs are asymmetrical
What are serous membranes?
Bag like structures that cover the organs
- secrete fluid that acts as a lubricant so things can slide over eachoiner
What parts of The Body have contact with the external environment?
Inner tube of The Body (respiratory and digestive tracts)
- specifically at the oral/nasal orifices and the anus
What is the pericardium?
A serious membrane (sac) that covers the heart
The heart grows into it
What are the 2 parts of serous membranes?
Visceral
Parietal
What is the visceral layer of a serous membrane?
Layer that is closest to the organ system wall
What is the parietal layer of a serous membrane?
The outer layer closest to The Body wall
What happens in gut rotation?
Gut rotates and drags other structures with it?
Gut herniates out of the cavity because the cavity isn’t large enough
Normally body grows to accept gut coming back in should rotate and fold
Where is the serous membrane?
It lines The Body walls and covers organs
Fist t plastic bag
What is a potential space?
Small spaces that have the potential to become much larger
Expandable, not rigid
What is the technical definition of a potential space?
Region of The Body in which 2 surface membranes adjoin, separated only by a small fluid filled layer
Give 3 examples of potential spaces?
Serous membranes
Fascia planes
Collapsible tubes /space
What is a real space?
Spaces that remain open when empty
Rigid, usually consistent in shape
Include airways and rigid tides
Define intraperitoneal.
When organs + structures can be arranged as fully encased by peritoneum
Define retroperitoneal
Organs + structures partially encased in peritoneum
Describe where the sternal angle is.
Little dip / bump between clavicles?
Join between manubrium and sternum
→ marks point where costal cartilages of ribs articulate with sternum
Where is the second costal cartilage?
Lateral to sternal angle
First costal cartilage is difficult to palpate as it is under clavicle
Where is the apex of the heart?
At the 5th intercostal space below the nipple
Give 2 examples of real spaces.
Airways
Rigid tubes I spaces
How to orientate yourself when viewing a Ct scan slice?
Look at the slice as though you are looking up from the feet to the head →
How is connective tissue arranged?
In fascia and fascia planes
What is fascia?
A band or sheet of connective tissue (mainly collagen) beneath the skin that attaches, stabilizes, encloses and seperates muscles and other internal organs
Connective tissue layers which can be thin, thick fatty or loose
What are fascial planes?
Important anatomical communication routes for spread of pathology
What are the 2 types of fascia?
Superficial
Deep
What is superficial fascia?
- beneath the skin
- loose and fatty
- variable thickness
- contains conagen, fat cells + elastic tissue
- goes round
What is deep fascia?
- fibrous, strong and tough sheet
- ensheaths muscles and forms compartments
- forms routes for infection to spread
- consequences during a bleed
Give 5 anatomical landmarks.
Bone Muscle Tendon Ligament Apertures
What is the transpyloric plane?
Horizontal plane at L1 level
- goes through lumbar 1 vertebrae and pylons (value of stomach)
What is the midclavicular plane?
A vertical plane from the midclavicular point
- from clavicle in the middle
What is the mediastinum?
A division of the thoracic cavity
Plane passing from sternal angle to T4 -T5 divides it into:
- superior mediastinum = containing major vessels
- inferior mediastinum = anterior, middle, posterior
What are the 3 regions of the inferior mediastinum and what do they contain?
Anterior → tnymic glands
Middle → under sternal plane, heart + lungs
Posterior → diaphragm and oesphagus
Define foreman
Bony, hollow archway through which nerves + blood vessels pass
Hole
Define fossa
Shallow depression in bone surface
Pit or groove
Define apex
Pointed and of a conical structure
Define prominence
Protrusion or projection
Define adventitia
External chiefly connective tissue covering of an organ
- outer tissue covering
Define aponeurosis
Flat sheet/ribbon of tendon like material
- anchors muscle or connects it with moving parts
Define septum
Dividing wall / membrane between body spaces or masses of soft tissue
Define lumen
Comity or channel with a tube / tubular organ
Define cortex
Outer or superficial part of an organ or body structure
Define Lamina
Flattened or arched part of vertebral area
Define bifurcate
Division into 2 branches
E G. Aortic bifurcation
Define Sulcus
Groove, furrow, trench
Why is knowledge of surface anatomy important?
Allows practitioners to assess what lies beneath skin surface by observation, palpation and manipulation of superficial structures
What fluid is found in the plural space?
Pleural fluid - small amount 10 - 20 ml of thin serous fluid
Lubricant during breathing
What are epithelial tissues?
Sheet of cells that line outer surfaces of organs and blood vessels
→ nearly all substances received or given off by The Body pass through epithelium layer
Give 5 main functions of epithelium tissues.
Protection Secretion Absorption Filtration Sensory reception
What are the characteristics of the epithelial tissue?
Polarised → epithelial cells have apical surface near the top and basal surface near the bottom
Supported by connective tissue
Presence of cell junctions
Attachment → attach basal laminar to connective tissue
Tissue is avascular → no blood vessels, receive nourishment through diffusion
Regenerative
What 2 words indicate the number of cell layers present in the epithelium tissue?
Single= one layer
Stratified - multiple layers
What 3 words indicate the shape of the cell?
Squamous
Cuboidal
Columnar
Describe the structure of simple squamous epithelium
Thin flattened cells
- used for exchange as substances can easily pass through
- located in alveoli, kidney, glomerulus, blood vessels linning, capillaries
Describe the structure of simple cuboidal epithelium.
Cube shaped calls with centrally located spherical nucleus
- used in absorption + secretion
- larger intracellular volume - greater number of contents
- located in secretory glands+ renal tubules
Describe the structure of simple columnar epithelium.
Large elongated column shaped cells, nuclei are usually at same level near basement membrane
- high organelle density used in absorption and secretion
- lines gl tract, uterus and portions of dietary tract
Describe the structure and location of stratified squamous epithelium?
Cells near surface are flat
- seen on outermost layer of skin
- present in areas of wear and tear = skin, vagina and anal cavity
Describe the structure and location of stratified cuboidal cells.
2 to 3 layers of cuboidal cells
- secretory functions lines sweat glands and seminiferous tubules
Describe the location of stratified columnar epithelium.
Protection
- larynx and male urethra
What is keratinized epithelium and where is it found?
Contains keratinized cells
- important for protecting underlying tissue
- found in external areas of wear and tear (skin and vocal cords)
Where is non keratinised epithelium found?
In internal areas of wear and tear
- lines areas like oesophagus and mouth
What is pseudostratified epithelium?
Epithelium that appears stratified as the individual cell nuclei are irregularly positioned
- it is actually just single epithelium as au cells are attached to the basement membrane
Describe pseudostratified columnar epithelium.
Epithelium that usually lines tubes of respiratory system.
- goblet cells scattered throughout tissue - secrete mucus
- cilia - hair like projections
What are absorptive cells?
Simple columnar cells with villi/microvili that increase absorptive surface - goblet cells= secrete mucus
What epithelium is present in the alveoli?
- Flattened squamous epienelium = gas exchange
2. Dome shaped cuboida epithelium in lumen - secretes surfactant to cover alveolar surface and reduce surface tension
What epithelium is present in the trachea?
Pseudo stratified epithelium with goblet cells and cilia, it is useful at clearing the airway
What epithelium is present in the urinary tract?
Bladder = transitional epienelium that changes in response to tension
- when organ walls contract → tissue stretches and appears thinner
- usually lines ureter, bladder and parts of urethra
What is the basement membrane?
Sheets of matrix at interface of functional tissue (parenchyma) and support tissue (stroma)
- composed of type iv collagen, glycoproteins, fibronectin (from fibroblasts) and glycosaminoglycan
What are the 5 functions of the basement membrane?
Adhesion
Partition
Barrier (has selective permeability)
Anchorage for cell organization - basal cells
Controlling growth and differentiation Of basal cells
What are cell junctions?
Junctional complexes that bind cells together and to underlying tissues
What are the 3 classes of cell junction?
Occluding
Anchoring
Communicating
What are occluding cell junctions?
Cells are seized together in sheets forming an impermeable barrier
What are anchoring cell junctions?
Attach cells and their cytoskeletal to other cells and extra cells in matrix
Mechanical support
What are communicating cell junctions?
Allow exchange of chemical and electrical info between cells
Name the 5 types of cell junction.
Tight junction Adherens junction Desmosome Gap junction Hemidesmosome
What is a tight junction?
Impermeable, prevent molecules from passing through intracellalar space
Prevent entrance of extracellular molecules into cell
What are adherens junctions?
Join an actin bundle in one cell to a similar bundle in a neighbouring en
What are desmosomes?
Anchoring junctions join the intermediate filaments in one cell to another - like a molecular Velcro forming an internal tension reducing network Of fibres
What are gap junctions?
Communicating junctions that allow the passage of small ions and molecules for intracellular communication
What is a hemidesmosome?
Extend into extracellular matrix and interact with extracellular membrane material’s and attach to basement membrane
Anchors cells to basement membrane
What is the role of a gland?
To synthesise and secrete complex molecules like hormones.
What are exocrine glands?
Release chemical substances through ducts to the outside of the body or onto another surface eg epithelial surface
What are the 3 types of exocrine secretion?
Mecrocrine= secretion by exocytosis Apocrine = shipping a portion of cytoplasm Holocrine= shipping interior cells from linining of one duct
What are endocrine glands?
Release chemical substances directly into bloodstream or tissues of the body
Secrete hormones
Ductless glands
Eg pituitary + thyroid glands
What forms can exocrine glands take?
Simple or compound (branched)
Tubular, acinar, mixed
What is Adenocarcinoma?
Cancer of glandular epithelium
- invasion of surrounding stromal tissue to spread tumour
- affect or access blood, lymphatic system
How is endocrine function regulated?
Through neural connections in the brain via the hypothalamus and pituitary gland
What is the apical surface of the epithelium?
Faces the external environment/lumen
- has no specialisations
What is the lateral surface of the epithelium?
Faces the sides of adjacent cells, has junctions
What is the basal surface of the epithelium?
Has basement membrane
Name the 3 layers of the skin
Epidermis
Dermis
Hypodermis/subcutis
What is the epidermis?
Outer layer of the skin made up of stratified squamous epithelium which is keratinized - has keratinocytes
- acts as protective shield
- develops from surface ectoderm at 4th week oflife
What is the dermis?
Made of dense connective tissue, contains collagen l, firbroblasis, elastin, blood, nerves and receptors
- divided into 2 types
- provides structure and support
What are the 2 types of dermis?
Papillary
Reticular
What is the papillary dermis?
Uppermost layer of the dermis, intertwines with ridges of the epidermis
- composed of fine + loosely arranged collagen fiber
What is the reticular dermis?
Lower layer of the dermis, found under papillary dermis
- composed of dense irregular connective tissue, densely packed collagen fibres
- primary location of dermal elastic fibres
What is the hypodermis ?
Composed of adipose tissue, is the main blood supply for the rest of the skin (blood vessels and capillaries)
- derived from the mesoderm
- acts as insulation and padding
What is the role of the skin?
Protection
- from uv light, chemical, thermal and mechanical injury, resistance to sheering, invasion
What are the 4 functions of the skin?
Act as a barrier → due to tight junctions in cells that make up skin, barrier is water tight
Sensation → neurons and sensory cells are sensitive to touch, pressure, pain, temperature
Thermoregulation → insulator, contains subcutaneous fats, heat loss via sweat, vasodilation and vasoconstriction
Metabolic functions → synthesises vitamin d3
How are internal tissues protected?
By immune system cells
Name 4 skin appendages
- Hair
- nails
- arrector pills
- sebaceous glands
- sweat glands - apocrine and eccrine
What is the arrector pili?
- Involved in thermoregulation
Muscle that controls the movement of hair follicles when erected hair stands up straight, traps a layer of hair between skin allows heat retention
What are sebaceous glands?
Associated with hair follicles
- secrete sebum (lipid mixture) into hair follicle for waterproofing
What are the 2 types of sweat glands?
Eccrine → ducts open onto skin release sweat for evaporation (thermoregulation)
Apocrine → localised, responsible for scent production (puberty)
What are the 4 recepto-rs?
Pacinian corpuscle = pressure (in connective tissues)
Meissner’s corpuscle= light, touch, pressure (under epidermis)
Ruffini corpuscle= skin stretching. (skin and joints)
Free nerve endling= pain, itch, temp
What are the functions of ground substance in the dermis?
Binds water
- allows nutrients, hormones, waste products to pass through dermis
- acts as lubricant between collagen and elastic fibres during movement
- provides bulk = shock absorber
What are the 4 epidermal cell types?
Keratinocytes
Melanocytes
Langernans cells
Merkel cells
What are keratinocytes?
Make up 95% of cells
- stratified squamous keratinizing epithelial cells
- produce keratin = structural protein
What are melanocytes?
Pigment synthesising cells → skin and hair colour
- neural crest derived cells in basal layers
Melanosomes in cytoplasm contain melanin + passed to keratinocytes - scattering uv light to protect skin
What are langerhans cells?
Present in all layers - mostly in stratum spinosum
- antigen presenting tens - immune cells
What are Merkel cells?
Present in touch areas
- connected to keratinocytes and sensory nerves
What is the role of hemidesmosomes?
To anchor epithelium to basement membrane
What are the 5 layers of the epidermis?
Stratum Corneum (outer) Stratum lucidium Stratum granulosum stratum spinosum Stratum basale
How is the epidermis multilaminar?
Basal cells divide continuously to give rise to the layers above - migratory cycle
- takes 30 days from basal to stratum corner
They become progressively more differentiated
Describe the structure of the nail
Root, nail plate and free edge - plate lies on highly vascularised nail bed
Paroncnyium = soft loose tissue surrounding nail border - susceptible to infection
- physical protection
Onychocryptosis = ingrown toenail
What is cellulitis?
Infection of deeper skin layers
- caused by strep pyogenes specifically affects superficial dermis and subcutaneous fat.
- erysipelas is also an infection caused by strep pyogenes = but it is an infection of superficial skin layers
What is impetigo?
Due to staphylococcus
- sub corneal blisters sometimes with pus
- bursting + spreading results in yellow crusting of skin
- nignly contagions
What is the stratum basale layer of the epidermis.
Deepest layer that is connected to basement membrane by hemidesmosomes
What is the stratum spinosum?
Contains several layers of keratinocytes attached to eachother by desmosomes
What is the stratum granulosum?
Contains cells filled with keratohyalin granules that when secreted are responsible for epidermal waterproof barrier
What is the stratum corneum?
Most superficial layer
No nuclei and are continuously shedding off (desquamating)
What are somatic motor nerves?
Supply skeletal muscles that we can control voluntarily
What are somatic sensory nerves?
Detect sensations that we are consciously aware of
- pain, touch, pressure, temp
What is a dermatome?
Area of skin in which sensory nerves derive from a single spinal nerve root
What are automatic motor nerves?
They stimulate smooth muscle to contract. In response to changes defected by automatic sensory nerves
What are automatic sensory receptors?
Can sense changes in ph and stretch but not pain
What is a partial thickness burn?
-> burns where not all of the skin layers are destroyed
First degree burn - epidermis (outer layer) are damaged
Second degree burn -epidermis and partially epidermis are damaged
What is a full thickness burn?
Third degree burn affecting all layers and some underlying tissues
- tissue oedema - loss of plasma proteins + imbalance of homeostatic mechanisms
- capillary beds off dermis + nerves and receptors of hypodermis are damaged
