tissues of the body

a collection of specialised cells that perform a particular function

• smear
• curettage
• needle
• endoscopic
• transvascular
• direct incision

glutaraldehyde/formaldehyde

maintains structure during handling and make cell parts visible

processing can lead to shrinkage artefacts

• H=haematoxylin - a basic dye stains nuclei blue
• E = eosin - stains cytoplasm pink

• blue nuclei
• pink collagen fibres

• phase contrast - used to study cell cycle as not in a vacuum and doesn't require staining
• dark field - used for smears as it improves contrast of transparent unstained specimens
• fluorescence - early diagnosis of TB and meningitis
• confocal - used to build 3D images

the minimum distance at which two points can be distinguished - electron microscopes have finer resolutions as electrons have a smaller wavelength than light

• heterochromatin - DNA not in active synthesis
• euchromatin - active in RNA synthesis

sheet of contiguous cells of varied embryonic origin that cover the external surfaces of the body and line the internal surface

• muscle
• nervous
• connective
• epithelial

• simple squamous - lining heart and blood vessels (endothelium), pleural and peritoneal cavities (mesothelium), and epithelium
• stratified squamous - found in oral cavity, vagina and oesophagus, can be keritanised - the skin
• simple cuboidal - line ducts of exocrine glands - kidney tubules and thyriod
• simple columnar - secretion of enzymes and mucus line the GI tract and large excretory ducts of glands
• pseudostratified ciliated - respiratory epithelia, upper resp tract, ear, nose.
• transitional - allows for distension and protection - bladder and ureter

they have the capacity to regenerate - eg. wound healing, replacement of skin, GI lining, uterine after menstruation

metaplasia - changing type - eg. resp epi - stratified squamous in heavy smokers

neoplasia - form carcinomas

• lining the surfaces of open cavities
• the GIT, resp tract, reproductive and urinary tract

• epithelium
• basement membrane
• lamina (tunica) propria
• muscularis mucosa

• mucosa/mucous membrane - contains glands in SI
• submucosa - dense irregular CT with large vessels and nerves
• muscularis externae/ muscularis propria - inner circular and outer longitudinal layer - peristalsis
• serosa/adventitia

• ureters urinary bladder and urethra transitional epi
• lamina propria - fibroelastic
• muscularis externae is thick

an epithelial cell or an aggregation of epithelial cells specialised for secretion

• endocrine secretion is straight in to the blood stream
• exocrine glands have ducts

• by STRUCTURE -
• - unicellular/multicellular
• - simple tubular/simple branched/simple coiled/simple acinar/simple branched acinar/ compound tubular/compound acinar
• by NATURE OF SECRETION -
• - mucus - high in mucins stain poorly with H&E
• - serous - high in enzymes, watery - stain pink with H&E
• by METHOD OF SECRETION -
• - merocrine - exocytosis
• - apocrine - non membrane bound structure ends up outside cell in a droplet
• - holocrine - disintergration of whole cell releases all contents this happens with sebaceous glands cells

coupled endo and exocytosis

packing, concentrating and modifying proteins from the RER

allows specificity by offering complex shapes

• nervous
• endocrine
• neuro-endocrine
• negative feedback

• goblet cells in jejunum, colon
• salivary glands
• pancreas - enzyme part

• thyroid
• parathyroid - chief cells secrete PTH
• adrenal gland

• MEDULLA
• - NA and A
• CORTEX
• - zona reticularis - androgens
• - zona fasiculata - glucocorticoids - cortisol
• - zona glomerulosa - mineralocorticoids - aldosterone

• mostly derived from mesoderm
• functions = support, defence, transport, repair
• mainly extracellular components with few cells

• embryonic - mesenchymal, mucous
• adult - loose, relicular, adipose, dense irregular, dense regular (collagenous/elastic)
• specialised - supporting (bone/cartilage), blood

• cells - mesenchymal cells
• extracellular - fine reticular fibres (thin branching carbohydrate coated type III collagen) and small blood vessels

• cells = fibroblasts
• extracellular = irregular collagen bundles

found deep to fetal skin and in the umbilical cord

• cells = fibroblasts, macrophages, plasma cells, mast cells, adipocytes
• extracellular = slender long collagen bundles, elastic fibres, reticular fibres, ground substance

ground substance is composed of GACs, proteoglycans and glycoproteins it forms a matrix for cell adhesion

found in superficial fascia/subcutaneous tissue, organs, between fasicles...

• cells = reticular cells, lymphocytes and macrophages
• extracellular = reticular fibres

classic lymph tissue - lymph nodes

cells = closely packed adipocytes separated by thin sheets of extracellular reticular and collagen fibres

subcutaneous fat

• cells = fibroblasts, macrophages
• extracellular = haphazard, thick, wavy collagen bundles and some reticular and elastic fibres

dermis, deep fascia, periosteum

• cells = parallel (few) rows of flattened fibroblasts
• extracellular = densely packed regularly arranged collagen fibres

tendons, aperneurosis

• cells = rows of flattened fibroblasts
• extracellular = bundles of thick elastic fibres - made from elastin

found in the lungs

• genetic defect on chromosome 15
• underdevelopment of elastic fibres
• heart/blood vessels/eyes/skeleton
• long fingers...

• collagen abnormality > joint dislocations and hyperextensibility
• autosomal dominant inheritance
• dissecting aortic aneurysm at an early age

• epidermis
• epidermal basement membrane
• dermis

• epidermis has 4 layers -
• - stratum corneum - stacks of dead cells called squames key function = protection
• - the granular layer - contains keratohyalin granules and other fibrous proteins which degrade the phospholipid membrane and xlink proteins - this is where the keratinocytes lose their membrane and become cells of the stratum corneum
• - the prickle cell layer - daughter keratinocytes terminally differentiate and lose the ability to divide
• - the basal layer - keratinocyte mitosis

30 - 40 days

- melanocytes are dendritic cells of neural crest origin they occur at intervals along the basal layer and produce melanin in darker skin there are the same amount they are just more active

- langerhans cells are dendritic cells of bone marrow origin they are scattered through the prickle layer and are designed to present antigens to Tcells mediating the immune response

• tough, fibrous, vascular layer, fibroblasts synthesis the
• extracellular matrix which contains collagens and elastin.

• The other main components = blood and lymph
• vessels. mast cells and nerves

• hair follicles
• sebacous gland
• nails
• sweat glands

• protection
• barrier
• sensation
• thermoregulation
• sociosexual communication

• leprosy
• diabetic sensory neuropathy
• psorasis
• hyperhidrosis
• acne
• alopecia areata
• keloids
• vitiligo
• allergic contact dermatitis
• basal cell carcinoma/malignant melanoma

• fetal skeleton
• costal cartilages
• articulating surfaces of bone
• C-rings of the trachea
• pubic symphsis
• ...

• hyaline
• elastic
• fibrocartilage

• most common
• can ossify in old age and disease
• makes up fetal skeleton remains in adult as costal cartilages, thyroid cartilage, articular cartilage, C rings of the trachea

• matrix is rich in collagen and elastin fibres
• doesn't calcify or ossify with age
• found in the ear canal and epiglottis

• irregular dense fibrous tissue with few chondrocytes
• found in symphsis, intervertebral discs, articular discs in the knee joint and the sternoclavicular joint

• avascular
• strong somewhat pliable
• firm proteoglycan matrix
• the cells are chondrocytes they form chondroblasts which secrete matrix trapping the cell in lacunae - they are then called chondrocytes
• most cartilage (NOT fibrocartilage) is surrounded by a dense irregular connective tissue called perichondrium which vasularises the cartilage by diffusion

• INTERSTITIAL GROWTH - chondrocytes divide within lacunae to form isogenous groups
• APPOSITIONAL GROWTH - is adding new cells to the surface but requires undifferentiated cells

• little capacity to repair
• fibrous/scar tissue is laid down by the perichondrium

• 65% inorganic - calcium phosphate etc.
• 35% organic - mostly collagen

• compact/dense/cortical
• spongy/cancellous/trabecular/medullary

• spongy bone has large open cavities surrounded by plates of bone
• compact bone is harder it has smaller cavities and thicker lamellar
• spongy bone contains bone marrow

• bone is always covered and lined by soft connective tissues
• the marrow cavity is lined by endosteum
• the periosteum covering the bone has an outer fibrous layer of collagen fibres and fibroblasts and an inner osteogenic layer consisting of an osteoprogenitor layer and osteoblasts
• the periosteum is fixed to the bone by sharpeys fibres and damage/trauma to the periosteum is very painful
• bone matrix is formed by osteoblasts which are derived from osteoprogenitor cells as they lay down the matrix they become trapped in lacunae and are referred to as osteocytes.
• osteocytes have long processes which are housed in canaliculi which are tunnels that lead to haversian canals which contain blood vessels
• the osteocytes that join one haversian canal to another are known as osteons
• haversian canals are joined to each other by volkmann's canals

• bone is continuously being remodelled - osteoclasts break it down and osteoblasts rebuild it.
• 1. haematoma - fibrin clot and bone fragments
• 2. procallus - inflammatory cell influx debris cleared
• 3. callus - fibrocartilage
• 4. healing - osteoprogenitor cells from periosteum lay down sleeve of bone - starts as spongy bone

bone forms from pre-existing tissue which is replaced

• there are two types of ossification:
• - intramembranous - bone development begins in highly vascularised CT, it begins at the primary centre of ossification and osteoblasts lay down osteoid - a non calcified matrix which later becomes calcified, the osteoblasts then become osteocytes.
• - cartilage is replaced, the primary centre is the diaphysis/shaft the secondary centres (the epiphyseal growth plates) occur at the epiphysis

flat bones of the skull

long bones

congential and often hereditary shortness of limbs - thin epiphyseal growth plates

• brittle bones
• abnormal collagen synthesis

• low growth hormone - pituitary dwarfism
• high growth hormone - gigantism/acromegaly(inc. in diameter)
• sex hormone deficiencies - epiphyseal growth plates don't close - tall stature
• thyroid hormone deficiency - cretinism
• high PTH - decalcification > inc. # risk

• RBCs - 120 days
• platelets - 10 days
• neutrophils - 2-4days
• lymphocytes - 1 day - years

progentitor stem cells in the bone marrow differentiate into myeloidblasts which are precursors for erythrocytes, granulocytes, monocytes and platelets. Lymphoblasts are precursors for lymphocytes

various cytokines regulate the rate of division and differentiation

erythropoetin released from pertitubular endothelial cells in the kidneys

• multi-lobed nucleus
• functions = chemotaxis and phagocytosis

• bilobed nucleus
• orange granules

• large dark purple granules
• release histamine and heparin
• mediate acute inflammation

• small round blue particles from cytoplasm of megakaryocytes in bone marrow
• activation leads to adhesion and aggregation and acts as a binding site for clotting factors

• smooth
• skeletal
• cardiac

• striated
• voluntary
• pink due to myoglobin and vascularisation
• fibres are long, multi-nucleated and cylindrical
• RED = slow lots of myoglobin
• WHITE = fast - easily fatigued

• number of fibres
• amount of hypertrophy

muscle > fascicle > fibre (cell) > fibrils packed in parallel with organelles organised between them, the sarcotubular system allows for depolarisation to be spread across the fibre by T tubules > myofibrils are made up of myofilaments which are actin and myosin

• the muscle sheath is epimysium
• surrounding each fascicle is perimysium
• surrounding each fibre is endomysium

• double helical strand
• troponin is distributed along it attached to tropomyosin

• 1. a nerve impulse arrives at neuromuscular junction causing release of ACh, depolarisation of the end plate and release of calcium
• 2. calcium binds to troponin which changes its shape and moves tropomysin away from the binding site of the actin so that the myosin filaments can form a cross bridge
• 3. the breakdown of ATP releases energy so myosin can pull the actin - shortening/contracting the muscle
• 4. myosin detaches from the actin and the cross bridge is broken down when ATP binds to the myosin to the myosin head when the ATP is broken down by myosin ATPase the power strike can be repeated

nerves attach at the motor end plate, one per fibre

• skeletal muscle has a small regenerative capacity but gross damage is repaired by CT and leaves a scar
• in nerves or blood supply is interrupted muscle fibres degenerate and are replaced by fibrous tissue

• non - striated
• involuntary
• found in walls of GI tract, resp tract, walls of ducts, glands, arteries, veins, large lymphatics and in the muscles of the eye
• the cells are long and spindle like often embedded in thin elastic fibres
• their contraction is slower than skeletal muscle and their actin and myosin arrangement is less ordered.

• striated
• involuntary
• found in the heart
• has elongated nuclei, which are central in the fibres, intercalated discs, fibres contain large numbers of sarcosomes, the T tubules lie at the Z bands

• ensure rapid spread of impulses
• contain fewer myofilaments, fibres and far fewer intercalated discs

NO repairs with fibro-connective scar tissue

• every two weeks
• muscle continuously remodels
• can atrophy and hypertrophy very quickly

• auto-immune destruction of end plate ACh receptors
• more common in females
• characterised by muscle weakness without sensory loss

treat with ACh esterase inhibitors

• myasthenia gravis
• botulism - toxins block ACh release
• organophosphate poisoning - irreversible binding of AChE > asphyxiation

• complete lack of dystrophin, muscle tears itself apart calcium enters and causes death and necrosis
• death in late teens from resp failure
• recessive defect on X chromosome

• genetic disorders
• muscle weakness and wasting
• replaced by fat and CT

• CNS
• PNS > ANS > sympathetic/non-sympathetic

• vast numbers of neurones supported by neuroglia, components sorted into grey and white matter
• the CNS is the brain and the spinal cord
• most neurones in the CNS are multipolar

nerve cell embedded in neuroglia

the processes is the processes of the nerve cells embedded in neuroglia

• astrocytes
• oligodendrocytes
• microglia
• ependymal cells

• cranial and peripheral nerves made up of bundles fibres
• divided into motor/efferent and sensory/afferent

• fertilisation > zygote
• cleavage > morula
• compaction > embryoblast/trophoblast/blastocyst cavity
• hatching > loss of zona pellucida
• beginning of implantation
• week 2 - trophoblast > syncytiotrophoblast + cytotrophoblast and embryoblast > epiblast + hypoblast (bilaminar disc)
• completion of implantation
• formation of primary yolk sac lined by hypoblast cells
• formation of secondary yolk sac from pinching off of primary yolk sac

formation of the primitive streak

• all major structures and systems formed
• GASTRULATION - primitive streak defines the axis it is made up of the pit, node and streak
• epiblast cells migrate towards the primitive streak and invaginate displacing the hypoblast cells and creating the trilaminar disc
• NOTOCORD - the epiblast cells that invaginate through the cranial part of the primitive pit form a solid rod of cells down the midline - this drives neuralation
• NEURALATION - formation of the neural plate and the neural tube - notocord causes thickening of overlying ectoderm and the edges fold round creating a tube.
• MESODERM - the paraxial mesoderm becomes organised into segments, in pairs called somites, there are 31 pairs
• FOLDING - cephalocaudal and lateral

• ectoderm
• mesoderm
• endoderm

• dermatome - skin section - dermis
• myotome - muscle section
• sclerotome - hard tissue section - bones

give rise to repeating sections such as vertebrae, ribs and intercostal muscles.

• nervous system
• epidermis

• muscle
• bone/cartilage
• CVS

• epithelium of the resp and GI tracts
• glands