Specialised tissues Flashcards by Neysa Patel

How are epithelial cells organised?

Shape:
-Squamous
-Cuboidal
-Columnar
Stratification
-Simple
-Stratified

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What is the function of simple squamous epithelium and where could it be found?

Allow passage of materials by diffusion and filtration
Secrete lubricating substances
Found in alveoli, lining of heart and vessels

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What is the function of simple cuboidal epithelium and where could it be found?

Secretes
Absorbs
Found in ducts and secretory portions of small glands and kidney tubules

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What is the function of simple columnar epithelium and where could it be found?

Absorbs
Secretes mucus and enzymes
Found in bronchi, uterine tubes and uterus

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What is the function of pseudostratified columnar epithelium and where could it be found?

Secrete mucus
Cilia moves mucus
Found in most of upper respiratory tract

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What is the function of stratified squamous epithelium and where could it be found?

Protects against abrasion

Found in oesophagus, mouth, vagina

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What is the function of stratified cuboidal epithelium and where could it be found?

Protective tissue

Found in sweat, salivary and mammary glands

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What is the function of stratified columnar epithelium and where could it be found?

Secretes
Protects
Found in male urethra and some gland ducts

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What are the different cell types found in the nervous system?

Neurones
Asterocytes
Oligodendrocytes
Schwann cells
Microglial cells
Ependymal cells

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What are the different types of neurones and how do they differ?

Unipolar - one axonal projection
Pseudo-unipolar - 1 axonal projection that splits into 2
Bipolar - one dendritic and one axonal projection
Multipolar - numerous cell projections, mostly dendrites and one axon

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Define neurone

CNS excitable cells that have heterogeneous morphology and do not divide

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What are the functions of an astrocyte?

Maintain CNS integrity and structure
Allow repair of neurones
Can become immune cells
Maintain homeostasis by clearing up ions and neurotransmitters, and any excess water

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What is the function of oligodendrocytes?

Provide myelin for neuronal axons

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What is the function of schwann cells?

Myelination of a single axon

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What is the function of a microglial cell?

Acts as a specialist brain macrophage

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What is the function of an ependymal cell?

Lines CSF vesicles and regulates product

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What are the components of a neurone and their functions?

Soma - cell body w nucleus and ribosomes
Axon - long nerve fibre
Dendrites - Receive signals from other neurones

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Explain how function is conveyed by generation of the resting membrane potential

RMP is due to an ionic imbalance
High EC Na+ high IC K+
Process of action potential causes brief depolarisation that is propagated along axon

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What is the ultrastructure of skeletal muscle?

Bundles of myofibres:

large and cylindrical
multinucleate
packed with myofibrils (gives striated appearance)

What are functional characteristics of skeletal muscle?

Attached to bone
- Produces movement of the body
Antagonistic muscle pairs (flexor and extensor)

What are the stages of excitation-contraction coupling in skeletal muscle?

1) AP propagates along sarcolemma (myofibre membrane) & t-tubules
2) Depolarisation activates dihydropyridine receptors
3) Conformational change in DHPR
4) Change transmitted to ryanodine receptors on sarcoplasmic reticulum
5) RyR opens and Ca2+ released from IC stores
6) Depolarisation results in increase in IC Ca2+
7) Rise in IC Ca2+ initiates contraction (sliding filament theory)

What is a sarcomere?

Functional unit of muscle that lies between two z lines

What does a sarcomere consist of?

Z-lines define lateral boundaries of sarcomere
Contains:
-Actin
-Myosin
-Titin
-Nebulin
-Tropomyosin
-CapZ and Tropomodulin

What is the sliding filament theory?

1) Ca2+ causes troponin movement from tropomyosin chain
2) Movement exposes myosin binding site on actin chain
3) Charged myosin heads bind to exposed site on actin filament
4) Binding and discharge of ADP causes myosin head to pivot (power stroke)
5) Actin filament pulled towards sarcomere centre
6) ATP binding releases myosin head
7) ATP hydrolysis recharges myosin head

What is the structure and function of cardiac muscle?

Cardiomyocytes (striated muscle) linked by intercalated discs (numerous gap junctions to allow rapid spread of AP) Sarcomere of cardiomyocytes have slightly different mechanism

What is are the differences between skeletal and cardiac E-C coupling?

Instead of dihydropyridine receptors, depolarisation opens VGCC and causes a Ca2+ influx in cardiac muscle

What are the effects of the Ca2+ release during cardiac E-C coupling?

Binds to RyR to induce more Ca2+ release Initiates contraction by binding to troponin Causes further depolarisation

What is the function of cardiac muscle?

Pump blood around body

What is the function of smooth muscle?

Lines hollow organs (e.g. blood vessels)

What is the structure of smooth muscle?

Spindle shaped cells | Not regular actin/myosin arrangement

What are the steps involved in E-C coupling in smooth muscle?

1) Depolarisation activates VGCCs 2) Ca2+-CaM (calmodulin) complex acticates myosin light chain kinase 3) MLCK phosphorylates myosin light chains that form cross bridges with actin filaments 4) Causes contraction

What is the structure of skin?

``` Stratum corneum Stratum granulosum Stratum Spinosum Stratum basale Basement membrane Dermis Hypodermis ```

What is the function of skin?

Protect against injury and pathogenic organisms Waterproofing and fluid conservation Thermoregulation Protect against radiation, absorption of UV radiation Vitamin D production Surface for grip Sensory organ

Describe the structure of the epidermis

Keratinocytes start at basement membrane and differentiate to move up the layers

What are the 3 main cell types found in the epidermis and their functions?

Langerhans cells - antigen presenting Merkel cell - sensory Melanocytes - melanin production

What are the 4 components of the dermo-epidermal junction?

``` Lamina lucida Lamina densa Anchoring fibrils Hemidesmosomes Anchoring filaments ```

Explain the development of melanocytes

Originate from neural crest Surround keratinocytes in stratum basale of epidermis 1 melanocyte:36 keratinocytes Melanocytes→melanin→melanosomes in nearby keratinocytes

What is the function of hair?

Protection (trauma/UV light) Sensation Thermoregulation Communication

What is the structure of hair?

``` Made from keratin Comprised of pilosebaceous units: -Follicle (epidermis invagination) -Shaft -Erector pili muscle -Sebaceous gland (produces sebum to lubricate hair) ```

What are the 3 types of hair and when are they found?

Lanugo - long, wispy, unpigmented, found in foetus/prenates/anorexics Vellus - unpigmented, wispy, covers whole body Terminal - thick, pigmented, has a medulla, found on head, pubic, underarms,

What is the structure of the hair follicle?

Infundibulum (gland opening - surface) Isthmus (erector pili - gland opening) Suprabulba (bulb - erector pili) Hair bulb (hair produced)

What are the 3 stages in the hair growth cycle and their features?

``` Anagen -growth -Highly vascularised and energy sensitive Catagen -Slow and stop of cell division -End of shaft keratinises and forms club -Dermal papilla and club moves towards base of muscle insertion Telogen -Hair is actively shed -Next anagen begins -Club hair takes 4-6 weeks to release ```

What is the effect of hormones on hair growth?

Testosterone paradox - Changes vellus to terminal during puberty - Can cause androgenic alopecia (balding) - XS androgen can cause hirsutism

What is are the functions of nails?

Protection Touch Communication

What is the structure of nails?

Dense keratin plate formed by germinal matrix Longitudinal ridging Proximal to distal curvature

How do nails grow?

Nail grows from germinal matrix

Specialised tissues Flashcards

Epithelial organisation; Epithelial specialisation; Nerve; Skeletal muscle; Cardiac muscle; Smooth muscle; Skin; Hair; Nails