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Flashcards in Histology Deck (35):
1

Definitions

-Cytology
-Histology

-Cytology: study of cell structure
-Histology: Study of tissues
-looks at how specialized cells come together to form tissues

2

Variety and Specialisation of cells

-Erythrocytes
-Adipocyte
-Myocyte

-Erythrocytes: Isolated, anucleate, flexible, abundant haemoglobin
-Adipocyte: have large lipid vacuole (main function of cell = fat storage), peripheral condensed nucleus (squished to side)
-Myocytes: Contractile filaments, respond to nerve input

3

Tissues - defn

-2 parts of an organ

-Tissues: Collections of cell performing related functions
-Are 2 parts to tissues;
1. Parenchyma: The functional cells within an organ
2. Stroma: The supportive role within an organ

e.g. In liver, parenchyma = hepatocytes; stroma = blood vessels, liver capsule and supporting CT

4

4 Tissue types (and the 5th one sometimes used)

1. Epithelium: Barrier b/w body and external environment
-line internal and external surfaces and lining of tubes
2. Muscle: Contraction; generation of force
3. Connective Tissue: Connect, anchor, support
4. Nervous Tissue: initiate and transmit nervous impulses
5. Round cells: Cells that don't form a coherent tissue but are individual cells that can move widely throughout body
-e.g. macrophages

5

Epithelia

-definition and features

-what it forms (3 things)

-where it stops

-Is continuous sheet-like layer of cells in combo with a thin, underlying, non-cellular basement membrane (blood vessels don't cross)
-forms barrier/active interface
-lines hollow organs and forms glands
-can even form more solid structures like the liver
-is supported by layer of ECM (basal lamina) -> made from type 4 collagen and other components

6

5 major functional categories of Epithelia

1. Protective: outer surface of body and opening of cavities (oesophagus)
2. Exchange: rapid exchange of gases (is therefore a thin endothelial lining)
3. Transporting: exchange of nongaseous materials; selective (gut and kidney)
4. Ciliated: move fluid across surface (respir. airways, female reproductive tract)
5. Secretory
i) Exocrine: Syn. and release secretory products to external environment (serous; salivary glands, pancreas)
ii)Endocrine: secrete products into extracellular space and the bloodstream (e.g. hormones)

7

Locations of Ciliated epithelia and Protective epithelia

-Ciliated epithelium: respiratory system and female reproductive system (move mucous coat along surface)
-in Female; ciliated epithelia is simple
-pseudostratified in Resp. system
-Protective epithelium = skin, lining mouth, oesophagus and anus
-skin: stratified epithelium (cells become squamous at top)
-highly keratinised (to avoid abrasion) = skin, footpad
-Less keratinised (to moisten surfaces) = oesophagus, orgal cavity, cervix, vagina

8

Layers of skin epithelia (5)
-from superficial to deep

-Stratum corneum (looks loose and wispy b.c. oils removed)
-Stratum lucidum
-Stratum Granulosum
-Stratum Spinuousus
-Stratum Basale

9

Types of cells in exchange epithelium and transport epithelium

-Exchange epithelium = simple squamous (allows easy exchange)
-Transport epithelium = columnar (small intestine)

10

Intracellular junctions (3 types)
-definitions

-Intercellular junctions: key feature of epithelial cells
-tight junctions restrict movement of material passing between transport epithelial cells
-Anchoring junctions: cell-cell (desmosomes) and cell-basement membrane (hemidesmosomes
-Gap junctions: cytoplasmic bridge allows electrical continuity and synchronised contraction
-allow communication
-cardiac myocyte have them

11

Secretory epithelia - what they do

-2 types

-Form clusters or glands rather than sheets and secrete substances
-may also be individual cells scattered (e.g. goblet cells
-Exocrine glands: have ducts and secrete onto internal or external surface (sweat, saliva, mammary)
-Endocrine cells: secrete into the bloodstream (e.g. Islets of Langerhans and insulin, thyroid, adrenal and pituitary)

12

Gland development

-Exocrine glands: hollow centre forms,, creating a duct that provides passageway for secretion sot move to surface
-Endocrine glands: Lose connecting bridge of cells that link them to parent epithelium -> secretions go straight to bloodstream

13

Kidney

-Nephron = renal coruscle + tubule
-blood filtered w/in kidney by passing along nephron
-filtered material passes along tubule of nephron
-transport epithelia found in proximal and distal convoluted tubules (and loop of Henle)
-blood enters and exits corpuscle -> filtrate forms and moves down convoluted tubule and through system
-filtrate modified
-Proximal convoluted tubule = fuzzy surface (has tiny microvilli to increase SA for absorption)
-lining of surrounding capillaries: endothelium (flat squamous cells)
-podacytes sit outside capillary -> comblike structure helps filter blood physically and electrically (has footlike structures)
*basement membrane, endothelium and podocyte = filtration system

14

Epithelium in Jejunum

-single layer of epithelium in internal surface -> renews v. quickly (renewal occurs in crypts)
-microvilli on epithelia (to increase SA)
-columnar epithelia

15

Epithelia in Liver - how cells arranged

-sheets of 6 sided hepatocytes arranged into lobules
-bathed by sinusoidal blood on 2 sides
-b/w each row of hepatocytes are canaliculi into which bile flows (eventually become ducts)
-bile helps break down fats

16

Muscle tissue - 3 types

-e.g.

*3 types;
1. Skeletal (striated): voluntary contraction, often agonist/antagonist
e.g. digphragm, tongue, extrinsic eye muscles
2. Smooth: involuntary contraction (autonomic)
e.g. intestinal wall w/ agonist/antagonist, blood vessels, uterus
3. Cardiac: involuntary contraction
-in heart
*contraction also important for wounds, scar tissues etc for regions to heal

17

Skeletal muscles

-what composed of and basic function

-features of muscle cells

-e.g.

-Composed of myofilaments -> has myosin (thick) and actin (thin) fibres
-divided in sacromeres that align (z disk aligns and makes striations)
-thick heads that can move along actin if ATP available
Features;
-fused cells (so in long parallel arrangements)
-many nuclei
-peripheral nuclei
-cylindical
*can regenerate
e.g. pharynx, diaphragm, tongue, eye, oesophagus

18

Skeletal muscles;
-slow vs fast twitch

-Slow twitch (aerobic): fatigue resistant (endurance, postural muscles)
-tend to be red (like chicken leg muscle)
-Fast twitch (anaerobic): strong, precise, fatigue rapidly, sprinters, digits
-tend to be white (like chicken breast)

19

Smooth Muscle

-features and e.g.

Features;
-Single cells w/ one central nucleus
-often 2 layers
-perpendicular
-no striations
-spindle-shaped
-diameter varies

-e.g. arrector pili, blood vessels, iris, airways, spleen, uterine wall, bladder

20

Cardiac muscle

-features
-can they regenerate?

Features:
-Striations
-branching
-central nucleus
-intercalated discs
-complex pattern

*can't regenerate as post-mitotic
e.g. Cardiac (heart)

21

Connective Tissues
-functions
-definition

-Structural and metabolic support for tissues/organs
-mediate nutrient and metabolite exchange w/ circulation
*cells embedded in mesh of fibres (elastin/collagen) and extracellular matrix
-have extensive ECM

-CT: any structure whose primary function is physical support for other structures
-in broader sense, also encompasses fluids

22

Types of CT (6)

-e.g. of each

1. Loose: Fibroelastic tissues that underlie epithelia (support, biological packing)
e.g. lamina propria of intestine, surrounds blood vessels
2. Dense: tissues for strength, flexibility, biomechanical action
-e.g. tendons, ligaments, muscle and nerve sheaths, basement membranes
3. Adipose tissue - fat storage (has no real matrix)
4. Cartilage: supporting tissue (ear, nose, knee menisci, joints)
5. Bone: calcified supporting tissue
6. Blood: water matrix - ions and dissolved molecules, soluble proteins

23

Osteoblast, osteoclast and osteocyte

Osteoblast: lays new bone matrix
Osteoclast: 'Clean' take bone away
Osteocyte: maintain bone (are w/in lacuni)

*same pattern works for other cell types (i.e. chondrocytes)

24

Chondrocytes - appearance

-Chondrocytes appear as cells w/in a matrix
-in cartilage, these cells appear in clusters (usu. of 2)

25

Nervous Tissue

-Nerve cells
-Glial cells

*definitions

-Nerve cells (neurons): specialised cells that receive, integrate and transmit info in form of electrical signals
-Glial cells (astrocytes for metabolic suuport, Schwann cells and ogliodendrocytes for myelin)

26

Basic neuron structure


-important features

-Cell body = nucleus and surround cytoplasm (perikaryon)
-in CNS or peripheral ganglia
-1 axon (efferent)
-arises from axon hillock
-ends at terminal boutons
-1 + dendrites (are afferent)

*are excitable cells and are post-mitotic (don't get replaced)

27

3 Types of Neurons

1. Multipolar Neurons: Multiple dendrites and are able to integrate input from many afferent neurons
e.g. interneurons and motor neurons
2. Bipolar neurons: single dendrite located opposite the axon hillock
e.g. sensory neurons of sight, smell and balance
3. Pseudounipolar neuroons: fusion of the origins of the axon and dendrite
e.g. primary sensory neurons (some in eye and ear too)

28

Organisation of the brain

-Grey matter = peripheral cortex
-folded in mammals to give sulci and gyri
-small foci of neuronal cell bodies form nuclei deeper w/in brain
-covered in 3 layers of CT meninges (pia mater, arachnoid and dura mater (outermost tough layer)
-cerebrospinal fluid fills subarachnoid space b/w arachnoid and pia mater

29

Glial cells

-Oligodendrocytes (called Schwann cells in PNS)
-Astrocytes (regulate metabolistes)
-Microglia
-Ependyma (simple cuboidal/columnar ciliated ep.
-lines ventricles and spinal canal

30

Synapses in Neurons

-Neurotransmitters in vesicles
-electrical signals cause release of chemical across synapse

31

Neuromusclar Junction

-what it is, basic features

-Similar to basic synapse structure
-Each motor neurone innervates from 1 >1000 muscle fibres
-axon ends at motor end plate, enveloped by Schwann cell
-Ach is neurotransmitter that is broken down after signal sent

32

Organ

-Organ: anatomically discrete collection of 2 or more tissue types (often 4) working together to perform a specific function

33

Organ Systems

-More than one organ interacting
e.g. Respiratory system

34

Sebaceous Gland

-Has hollow middle
-outside gland, epithelial cells rapidly dividing, cells mature and move to middle of gland
-Accumulates oily secretions (sebum)
-nucleus dies and whole cell bursts onto hair follicle -> comes out and goes onto skin surface
*Holocrine secretion: entire cell is shed

35

Sweat gland

-Simple tubular gland
-lined by cuboidal epithelium
-discharge secretions into tube