Exam I Flashcards
(183 cards)
1
Q
Bichat’s types of membranes and their characteristics
A
Organic(vegetative)- life of heart and other organs and was regulated by collection of small independnt thoracic brains (ganglic NS)
Animal- composed of symmetrical organs and include habit and memory and ruled by wit and intellect
2
Q
Marie Francois Xavier Bichat
A
- changed perception that organs contain tissues or membranes
- described 21 membranes w/o microscope
- divided membranes into organic and animal life
- brought down to tissue level
- disease attacked organs
3
Q
Giovanni Battista Morgagni
A
- showed that diseases were due to organ lesions not humoral imbalances
- brought diagnosis down to anatomical level
4
Q
Who won the Nobel Prize in Physiology/Medicine in 1906 and what did they do?
A
Golgi- created silver staining technique to stain nervous tissue.
Cajal- correctly interpreted the neural structure of the brain.
5
Q
Definition of histology and histopathology.
A
study of the microscopic anatomy of cells and tissue of plants and animals.
histopathology- study of abnormal or diseased tissue
6
Q
Humoral Pathology Concept and 4 humors
A
-concept that was prominent until the 18th century that suggested diseases were caused by an imbalance of the humors.
- blood
- phlegm
- yellow bile
- black bile
7
Q
4 basic types of tissue
A
- epithelial
- muscular
- nervous
- connective
8
Q
Rudolph Carl Virchow
A
- pioneered concept of pathology processes through application of cell theory
- “all cells from cells,” ex. maggots from trash
9
Q
Refraction of light definition and equation
A
-the bending of light while traveling through another medium
refractive index= velocity of light/velocity of light inside medium
refractive index of air= 1
10
Q
Light bending depends on:
A
- refractive index
- angle light hits surface
11
Q
Refractive power
A
measure of how much a lens bends light waves. Measured in diopters. (1/focal length)
12
Q
focal point
A
the point through which all parallel rays will pass after passing through each part of the lens
13
Q
focal length
A
distance from center of lens to focal point
14
Q
real image
A
-when an image is placed outside the focal point
- inverted
- can be projected onto a screen
- differs in size from real object (greatest magnification when short focal length and object is close to the focal point)
15
Q
Virtual image
A
-seen when object is placed inside the focal point
- not inverted
- cannot be projected onto a screen
- can be magnified
16
Q
resolution
A
the ability of microscope to distinguish between two objects as separate points, diameter of diffraction lines must be reduced
17
Q
resolution equation
A
d=0.61(lambda)/n sin(a)
lambda= wavelength of light n= refractive index of medium (n air =1, n oil= 1.4) sin(a)= angle of cone of light entering aperture n sin(a)= numerical aperture
18
Q
resolution in different microscopes
A
light microscope- highest is 0.5 micrometers (oil)
TEM- theoretically is 0.01A, but actual is 5-10A
19
Q
Components of light microscope and what it does
A
light source, condenser (focuses light), stage(holds specimen), objective lens(first set lenses), ocular lens(second set of lenses)
20
Q
Pros and cons of light microscope
A
- ability to magnify
- ability to resolve structural detail
- specimen must be thin
- little contrast in unstained specimen
21
Q
Phase Contrast Microscope
A
- -phase shifts become visible
- can examine unstained cells and tissue
- can examine living cells
22
Q
Fluorescent microscope
A
- detects molecules that emit light visible under UV
- detects naturally occurring fluorescent molecules such as vitamin A
- can detect stained molecules -> antigens/antibodies, fluorescent tracers in the body
23
Q
Confocal Scanning Microscope
A
-increases resolution by eliminating out of focus light
-can recreate 3D images
-uses a laser and moves it across the specimen
-very thin images created (1micrometer thick)
-out of focus images are subtracted
-
24
Q
Transmission Electron Microscope(TEM)
A
- utilizes a beam of electrons rather than light (heated tungsten filament)
- cathode
- anode(drives electrons through column)
- electromagnets
25
What are the series of steps used to prepare tissue for microscopic examination?
- fixing
- dehydration
- removal of alcohol
- embedding
26
What is fixing?
prevents further deterioration of the tissue and hardens the tissue prior to embedding and sectioning
27
What is one of the most widely utilized fixing agent and describe it according to lecture.
Formalin, can be used alone (buffer) or with other agents such as alcohol (causes shrinkage) and acetic acid (softens and counteracts shrinkage).
- reacts with amino acids to stabilize tissue
- not good if cytological detail is desired
28
What is an acid fixative good for?
An acid fixative fixes chromatin, nucleoli, spindle fibers, but not mitochondria or nucleoplasm.
29
What are the three acid fixatives discussed in class?
Carnoy's fluid- useful for preserving glycogen in animal tissues
Zenker's fluid- useful to view sharp detail, but must be washed carefully to prevent black precipitate.
Bouin's fluid- widely used fixative, but must there must be prolonged and careful washing cycles
30
What is a basic fixative?
Good for mitochondrial staining, but it dissolves chromatin
31
What is the basic fixative discussed in class?
Zirkle-Erliki- requires long fixing time and washing under water
32
What are the two TEM fixatives?
glutaraldehyde- preserves proteins by cross linking them
osmium tetroxide- reacts with lipids and imparts electron density to cell and tissue structure
33
What is dehydration?
Removing all the water from the tissue before embedding and infiltrating with hydrophobic material. Consists of washing tissue in increasing strengths of alcohol. Ethanol dissolves neutral fats
34
What is clearing?
replacing the alcohol with an agent such as xylene, cedar oil, CCl4
35
What is embedding?
moves the tissue through three paraffin baths, placing in a mold, and then hardening in a cold water bath
36
Embedding for TEM
- use of monomeric resin
- resin is then polymerized
- less than 1mm3
37
What is sectioning? And how is this done?
Sectioning is slicing samples into smaller samples utilizing microtomes or sharp razors. For TEM, sections are cut into 50-150nm sections using a diamond blade. The sample is then placed on a copper mesh grid (electrons pass through grid)
38
What do you need to do to prepare a stain?
- Paraffin must be removed using xylene.
- xylene is removed using decreasing alcohol strength to water
- stains are applied and then dehydrated
- alcohol is removed with xylene
- drop of cement and cover slip applied
39
Hematoxylin and eosin
- behaves like basic dye due to mordant
- hemotoxylin stains dyes nuclear and cytoplasmic material blue
- eosin stains cytoplasm and extracellular blue
40
Examples of stains
- orcein and resorcin fuchsin stains used to reveal elastic material
- silver impreganation is useful for reticular fibers and basement membranes
- Sudans are good for lipids
41
Describe basic dyes and give examples.
- react with anionic groups such as phosphate, sulfate, and carboxylic groups (all three groups available at high pH)
- tissues that react with this basophilic
- methyl green, methylate blue, pyronine G, toluidine blue
42
Describe acid dyes.
- bind to cationic groups (amino acids) in tissue using electrostatic linkages
- all have slightly different properties and can be used in sequence to see different things
- aniline(collagen), acid fuchsin(cytoplasm), orange G(red blood cells)
43
Metachromasia
A change in dye color after reacting with tissue components
44
What do histochemical techniques do?
techniques used to study the chemistry of cells and tissues
45
Perls' reaction
-demonstrate the presence of iron in tissue
46
Stains for lipids:
must use frozen sections because lipids are soluble in normal reagents. -Sudan IV, Sudan black, oil red O
47
Fuelgen reaction
detects aldehyde groups on deoxyribose using Schiff reagent
48
Periodic acid-Schiff reaction (PAS)
- PA cleaves carbon bonds to form aldehyde group
- Schiff reacts with aldehyde group turning pink
- detects polysaccahrides, glycoproteins, glycolipids, proteoglycans, glycosaminoglycans
- clinical application: biopsies of patients with glycogenoses (glycogen storage disease)
- best carmine does the same
49
RNA Stains:
-can be stained with basic dyes, but will need control slides to distinguish from other basophilic substances
50
Immunocytochemical stain definition and monoclonal antibodies
used to study specific antigens in tissue by using monoclonal (single immune response) antibodies.
-monoclonal antibodies are derived from activated B cell clones exposed to a specific antigen
51
Direct vs indirect labeling
direct: antibodies are conjugated directly with either fluorescent dye, gold or ferritin(TEM), or visible markers(light)
indirect: marker is attached to second antibody which is specific to the antigen that is being looked for
52
What tissue is found is most prevalent in the body?
epithelium
53
What are the different types of epithelium?
simple/stratified squamous, simple/stratified columnar, simple/stratified cuboidal, transitional, pseudostratified
54
What are the characteristics of epithelium?
- uniform geometric shape
- tightly bound together (tight junctions)
- little intercellular matrix
- display free surfaces (face lumen, surface, etc)
- cell exhibit polarity
- do not have blood vessels
- may be derived from the three germ layers
- can be innervated
- form secretory and excretory parts of glands
- line body cavities and cover body surfaces
- sits on top of basement lamina
55
What does cell polarity mean?
the cells have an apical end (top) that is in contact with the lumen and houses structures such as the microvilli, cilia, and sterocilia. The cells also have a basolateral side, which is where the cells come into contact with other cells. Connected via junction complexes and come into contact with basal lamina.
56
What are the components and functions of the basement membrane?
functions: selective filtration barrier, stabilization of tissue shapes, scaffold for embryogenesis and regeneration
components: composed of the reticular lamina and basal lamina. Basal lamina is next to the epithelia and is composed of type IV collagen and glycoproteins and is PAS+. Absent in lymphatic vessels and hepatic sinusoids. The reticular lamina is in contact with the connective tissue and is composed of argyrophilic fibers, reticular fibers, and glycoproteins.
57
What else can epithelia be identified by?
- keratin
| - apical structures
58
Basolateral modifications
-maintain conc differences (tight vs leaky barrier)
+barrier type is determined by the the complexes that hold the cells together
-anchored to basal lamina
59
Where are simple squamous epithelia found?
- lines lumina of duct, vessels, and other tubular structures
- walls of alveoli, Bowman's capsule, tympanic membrane, surface sof membranous labyrinth
60
Where are simple cuboidal epithelia found?
-kidney tubules, surface of ovary, pigmented epithelia of retina, kidney tubules, glands and ducts, terminal bronchioles, choroid plexus, anterior capsule of eye
61
Where are simple columnar epithelia found?
- ciliated: upper respiratory tract, uterine tubes, uterus, paranasal sinuses, central canal of spinal cord
- non-ciliated: cardia of the stomach, gall bladder, and excretory ducts of the glands
62
Where are stratified squamous cells found?
- heavily keratinized: epidermis and cornea
| - lightly keratinized or non: esophagus, vagina, lining of mouth, tongue, and epiglottis
63
Where are stratified cuboidal epithelia found?
- rare
| - anal mucosa, large excretory ducts, part of male urethra
64
Where are stratified columnar epithelia found?
- rare
| - conjunctiva of eye, adult sweat glands, pharynx, epiglottis, parts of male reproductive/urinary tract
65
Where can pseudostratified epithlia be found?
- ciliated: trachea
| - stereocilia: epididymis
66
Where can transitional epithelia be found?
urinary tract (urothelium)
67
What are the functions of epithelial tissue?
- covering and lining
| - glandular
68
Simple, non-ciliated columnar epithelium is most likely to be found associated with which of the following?
digestive tract
69
Junctional complexes are associated with which cellular domains?
basolateral
70
Transitional epithelium is associated with which of the following systems?
urinary
71
Although not common, stratified cuboidal may be found in which of the following areas?
part of the male urethra
72
Lightly keratinized stratified squamous epithelium is characteristic of which of the following locations?
vaginal epithelium
73
What are the components of the basal lamina?
- secreted by the epithelial layer
- laminin
- fibronectin
- type IV collagen (does not form fibrils)
- entactin
- proteoglycans
74
What are the characteristics of laminin?
- Composed of three different chains (alpha, beta, and gamma)
- has binding sites for integrins, type IV collagen, entactin, and proteoglycans
75
What are the characteristics of fibronectin?
-protein composed of two polypeptide chains cross linked by disulfide bonds
-has two forms: cellular and plasma
+cellular is part of extracellular matrix and is secreted by fibroblasts
+plasma is secreted into the bloodstream by hepatocytes
-has binding sites for heparin, integrins, collagen, and fibrin
76
What are the calcium dependent and independent CAMs?
Ca+2 dependent: cadherins and selectins
Ca+2 independent: integrins and immunoglobin superfamily
77
What are classical cadherins and what classes are involved in them?
-major components in calcium mediated adherins junctions
-form cis and trans homophilic dimers
classes include
+E-cadherins(epithelium)
+N-cadherins(nerve cells)
+P-cadherins(placenta)
78
Where are non classical cadherins found?
desmocollins, desmogleins, and desmosomes
79
What is the most common type of cadherin and is it's function?
E-cadherin and they are responsible for holding together epithelial tissues (cytoskeleton to cytoskeleton)
-binds to histidine-valine-alanine sequence
80
What are catenins responsible for?
Serve as a major interface between the cadherins that hold adjacent cells together and the actin cytoskeletons of those cells, link cytoplasmic end of cadherin with with cytoplasmic actin
Three forms:
- beta and gamma/plakoglobin(attached to cytoplasmic end of cADHERIN, BETA TRANSRIPTION COFACTOR, BETA ATTACHED TO ALPHA)
- alpha(binds directly to actin)
81
What are selectins?
- bind to carb group therefore are lectins
- involved in movement of leukocytes from blood to tissues
- binding site is carbohydrate recognition domain (CRD) at extracellular end
- calcium binding sites are found near CRD(required for binding activity)
82
What are the classes of selectins?
- P (associated with platelets)
- E (activated endothelial cells)
- L (leukocytes)
83
What are integrins?
- consist of two subunits (alpha and beta)
- binds to the intercellular cytoskeleton (actin) and the extracellular fibronectin and laminin (basement membrane) -> interacts with Arg-Gly-Asp sequence
- in hemidesmosomes link with tonofilaments
84
What are immunoglobins?
-possess an extracellular component with one or more folded domains
-members include
+N-CAM: neural, mediate both homo and heterophilic interactions
+I-CAN-1 and I-CAM-2: I-CAM-1 facilitated transendothelial migration of leukocytes
85
What are the categories of junctional complexes and what are their functions?
Adherens:
- anchor cells together and reinforce physical integrity
- can be found on basolateral surfaces
Occludens:
-establish an impermeable barrier between cells, prevents paracellular transport and maintains concentration differences
Gap Junctions:
-composed of pores that enable cells to exchange ions and other molecules that coordinate activities among cells in the tissue
86
What are the two types of junctions discussed in class?
Zonula:
- either adheren or occluden
- travel around the circumference and link all neighboring cells (belt like complex)
- attach to actin filaments
Macula:
- spot that are adheren and referred to as desmosomes or hemidesmosomes
- associated with intracellular intermediate fibers (tonofilaments)
87
What are characteristics of adherens and examples?
-anchoring junctions characterized by intercellular spaces which are filled with cadherin proteins
+desmogleins(found in epidermis and associated with pemphigus foliaceous)
+desmocollins
-anchored to cytoplasmic plaques (desmoplakin and plakoglobin)
88
What are hemidesmosomes?
-anchoring junctions that anchor the basal domain to the basal lamina
-consists of:
+cytoplasmic plate associated with intermediate filaments such as keratin
+a membrane plaque linking the hemi to the basal lamina via anchoring filaments and integrins
89
Pemphigus Foliaceous
a blistering condition affecting the adheren connecting the stratum spinosum and granulosum. The antibodies attack desmoglein 1. This causes blistering with the smallest amount of pressure.
90
Structure of zona occludens
- claudins and occludens are transmembrane proteins associated with junctional complex and are responsible for occlusive properties, attach intracellularly to ZO-2 and ZO-3
- other proteins include junctional adhesion molecules (JAMs) and nectin
- JAMs and nectin belong to the immunoglobin family and are stabilized via disulfide bonds and form cis-homodimers
- nectin is associated with afadin
- JAMs are associated with afadin and ZO-1
- all of these proteins interact with actin
91
What are focal adhesions?
- spots that anchor the cell to the extracellular matrix via integrins
- differ from desmosomes in that they connect to actin via proteins rather than keratin or tonofilaments
- -involved in tissue integrity or may rapidly turn over cells for movement
92
Describe gap junctions.
-a communicating junction that allows cells to directly communicate
-composed of connexons (clustered in patches and allow molecules 1.2nm in diameter through)
-close when Ca+2 is high
-responsible for chemical and electrical coupling
-pathologies include:
+congenital cataracts
+Charcot-Marie-Tooth neuropathy
93
The basal lamina is associated with which type of collagen?
Type IV
94
Which of he following types of cell adhesion molecules is associated with zonula occludens and desmosomes?
cadherins
95
Desmocollins and desmogleins belong to which class of CAMs?
cadherins
96
Which of the following serve as a major interface between the cadherins that hold adjacent cells together and their actin skeleton?
catenins
97
The extracellular domains of which of the following bind to molecules in the extracellular matrix such as fibronectin and laminin?
integrins
98
Which of the following are molecular complexes that anchor cells together and reinforce the physical integrity of tissues and the cells that make up the tissues?
zonula adherens
99
Which of the following are molecular complexes that primarily serve to prevent paracellular transport?
zonula occludens
100
What are some functions and characteristics of microvilli?
- fingerlike projections supported by cross linked actin bundles
- non-motile
- form a uniform brush border
- increase surface area for absorption
- intestinal epithelium and parts of renal tubule
101
What is the microvillus structure?
-actin filament core extending into a network of cytoskeletal proteins under apical side of cell
-distal end of actin filament core is capped by formin which interacts with the barbed end of the actin filament
+formin regulates the assembly of the actin filaments at the barbed ends
-core actin filaments are cross linked by villin and fimbrin
-core acts to connect the intermediate filaments of the web
102
Structure of stereocilia.
-similar structure as villi except longer and branched. Stereocilia are also non-motile.
103
What is the structure of the cilia?
-9 peripheral doublets (not complete microtubules) + central pair of microtubules (9+2)
each doublet consists of: 13 protofilaments, radial spokes extending to sheath around central pair, dynein arms projecting to beta unit
-cilia can carry cargo due to the dynein
104
What three components is the cytoskeleton composed of?
Microfilments, intermediate filaments, and microtubules
105
What are the basic functions of the cytoskeleton?
- assist in cellular division and movement
- distributes force between adjacent cells and the basal lamina
- maintains cell shape and functions in cell resiliency
106
What are the characteristics of actin?
- highly conserved among eukaryotes
- 7nm thick, 7micrometeres in length
- filaments can be organized in 3D networks and bundles
- directly or indirectly bind to extracellular components (transmembrane)
- can exist as monomers (G actin) or long chains (F actin)
107
What are the three main varieties of actin and where are they typically found?
- alpha actin (muscle)
- beta (non muscular)
- gamma (non muscular)
108
What is the difference between G actin and F actin?
- G actin has a binding site for ATP
- F actin binds with other monomers to form a filament...G actin constitutes F actin
- both displays polarity of the monomers
109
What are the steps of actin polymerization?
Polymerization can always be reversed
1. Nucleation: a trimer is formed and additional monomers can be added to the end.
2. ATP actin associates with the growing (barbed or plus) end of the microfilament, ATP is hydrolyzed into ADP following polymerization.
- rate of growth is proportional to the concentration in the cytosol
- ADP actin dissociates more readily than ATP actin
- barbed end grows 5-10x faster than the pointed end
- low conc of G actin favors disassembly
- intermediate conc favors treadmilling (equilibrium and zero net growth)
- higher conc favor growth from both ends
110
What are the two drugs that affect microfilament polymerization? What do they do?
Cytochalasins: bind to barbed ends and block elongation, can inhibit movements
Phalloidin: binds to actin filaments and prevents dissociation. Can be labelled with fluorescent dyes for visualization.
111
Why is actin a ubiquitous microfilament?
Has the same structure, but has the ability for the actin to bind to so many different locations is dependent on the actin binding proteins
112
What are the actin binding proteins discussed in class?
Spectrin- found in RBCs and link the cytoskeleton to the plasma membrane.
Dystrophin- binds cortical cytoskeleton to the plasma membrane, linked to muscular dystrophy
Villin and fimbrin- cross links microvilli
Calmodulin and myosin I- cross links actin to plasma membrane in microvilli
Alpha actinin- cross links stress fibers and actin to protein-plasma membrane complex complexes
Filamin- cross links actin in wide angles to form screen like gels
113
What are the actin binding proteins that control treadmilling?
Thymosine- captures actin monomers and prevents them from being polymerized.
Profilin- binds to actin monomers and prevents polymerization. Also facilitates exchange of bound ADP for ATP, favoring polymerization.
Gelsolin- destabilizes F actin and caps actin filaments, preventing loss and addition of G actin. In Ca, fragments filament and remains bound to barbed end.
Cofilin- triggers depolymerization at at minus end (ADP rich)
Arp 2/3- initiates growth of F actin from existing sides of existing filament, causing branching
Phalloidin- prevents depolymerization by binding to actin filaments.
Latrunculins- binds to G actin and induces F actin depolymerization
114
What are the characteristics of intermediate filaments?
- 8-10nm thick
- abundant in cells that undergo mechanical stress
- provide tensile strength (neurons and muscle)
- strengthen epithelial cells as desmosomes and hemidesmosomes
- head and tail domains have specific functions
- common monomer consisting of central alpha helical rod flanked by head and tail domains
115
How are intermediate filaments assembled?
-central rods of polypeptide form a coiled dimer (tail to tail and head to head)
-dimers associate in staggered antiparallel fashion to form tetramers (polymerized filaments have no distinct ends, no treadmilling and more stable than microfilaments)
tetramers assemble end to end to form protofilaments, 8 protofilaments are wound together to form these filaments
116
What are the functions of intermediate filaments?
- form a cytoplasmic network in most cells
| - associate with other cytoskeletal elements to form a scaffolding that organizes internal structure
117
What are the intermediate filament types? Give an example of each.
```
Type I: acidic keratin
Type II: neutral to basic keratins
Type III: vimentin, desmin, glial fibrillary acidic protein, peripherin
Type IV: neurofilaments
Type V: nuclear lamins
Type VI: nestin
```
118
What are the characteristics of microtubules?
- 25micrometeres in diamtere
- composed of tubulin dimers (alpha + beta unit)
- protofilaments are longitudinal rows of tubulin dimers
- consist of 13 protofilaments arranged parallel to form cylinder with a hollow core
- fast growing plus end and slowing growing minus end (display polarity)
119
Describe microtubule polymerization.
- tubulin dimers with GTP bound to the beta-tubulin associate with the growing end
- plus end grows more rapidly in the presence of low Ca+2
- after polymerization the GTP is hydrolyzed to GDP and tubulin is less stable
- dimers at minus end dissociate
- at high concentrations, the tubulin GTP is cleaved at a pace slower than the dimers are added
- if low conc of tubulin GTP, GTP from the plus end is hydrolyzed and the dimers are lost
120
What factors inhibit microtubule polymerization?
- colchines (arrest mitosis in metaphase, bursts cell open)
- colcemid
- vincristine (anti-cancer drug, vinblastin for Hodgkins lymphoma)
- vinblastin
121
What factor stabilizes microtubules?
Taxol (anti-cancer drug, used for breast cancer), binds to microtubules preventing depolymerization. Disrupts mitosis by affecting the dynamic assembly and disassembly of the mitotic spindle
122
What are the functions of the cytoskeleton?
- cell movement
- support and strength for cell
- phagocytosis
- mitotic spindle formation
- cytokinesis (splitting the cell after mitosis)
- cell to cell and cell to extracellular matrix adherence
- changes inc ell shape
123
What are the different types of transport along a filament and how do each of these occur?
Interciliary transport:
- anterograde transport of cargos along microtubule mediated by kinesin. (minus to plus end)
- deliver materials to plus end
- retrograde transport of cargos along microtubule via dynein
- disassembly of raft protein cargo-complex molecular motor machinery
Axonal transport
- anterograde transport of vesicles via kinesin (neurotransmitter)
- delivery to pre-synaptic cleft
- retrograde transport of vesicles via dynein
124
Compare myosin I and II.
Myosin I: one head, tail binds to cell membrane, head binds to actin, head moved toward barded (plus) end
Myosin II: two heads, tail binds to myosin II, head binds to actin, head moves toward barbed end
125
Compare kinesin and cytoplasmic dynein.
Kinesin and dynein: two heads, tails binds to vesicle, head binds to microtubule
kinesin head moves toward plus end, dynein head moves toward minus end
126
What is the outer leaflet of the phospholipid bilayer composed of?
- cholesterol
- phosphatidylcholine
- phosphatidylethanolamine
- sphingomyelin
127
What is the inner leaflet of the bilayer composed of?
-cholesterol
-phosphatidylethanolamine
-phosphatidylserine (negatively charged)
phosphatidylinositol (important in cell signaling, positively charged)
128
Glycolipids
- found only in the outer leaflet with carb facing out
- fatty acid tail is coupled with sphingosine to a carb head group
- create a cell coat involved in cell to cell interactions and conveys antigenicity
129
Cholesterol
-moderates membrane fluidity:
+in warm temps hardens membrane, making it less fluid and reduces permeability to small molecules
+at low temps prevents membrane from freezing and maintains fluidity
130
Glycocalyx
- not integral part of membrane
| - carb coat on extracellular surface composed of carb portions of glycoproteins and glycolipids
131
Lipid raft
- small patches of sphingolipids and cholesterol.
- these are areas that have receptors that move around and serve as a landing ssite for molecules that the cell wishes to ingest
132
Describe glandular tissue in general.
-composed of epithelial cells specialized for secretory function
-may remain incorporated within the epithelial layer (unicellular) or into the connective tissue (multicellular gland)
-may remain connected to epithelial layer -> exocrine gland
+exocrine secrets product via a duct from original connection to epithelial layer
-epithelial layer may degenerate, leaving the secretory tissue from its parent epithelial layer -> endocrine
+endocrine glands secretes product into surrounding blood vessel
133
Paracrine vs autocrine
paracrine: secretion affects neighboring cells, ex. growth factors
autocrine: secretion affects the cel that released the secretory product
134
How can you classify glands?
- number of cells comprising the gland
- shape of secretory portion
- type of secretion
- mechanism of excretion
135
What are some examples of unicellular and multicellular glands?
unicellular: Goblet cells of intestine and trachea, mucus cells of stomach, enteroendocrine cells
multicellular: includes most endocrine and exocrine glands
136
When is ductal branching observed?
- simple multicellular do not have branching
| - compound multicellular exhibit branching
137
What are the types of secretory shapes and where can they be found?
-tubular
+straight(crypts of Lieberkuhn in intestine)
+coiled: sweat glands
+branched: fundus, cardia, pyloric glands of stomach
-alveolar acinar): Meibomian glands of eyelid, sebaceous glands
-tubuloalveolar(-acinar): salivary glands, Brunner's glands of duodenum, mucus glands of esophagus
138
What are the different names for for both simple and compound ducts?
Simple:
- tubular
- coiled
- tubular branched
- acinar/alvveolar
Compound:
- branched tubular
- branched alveolar(acinar)
- branched tubuloalveolar(acinar)
139
What are the different types of secretion?
Serous
-watery, enzyme filled secretion (parotid)
Mucus
-thick, mucin containing secretion
Mixed
- combination of mucus and serous fluid
- acinus is typically mucus capped by a half moon shaped group of serous cells forming a serous demilune
140
Explain the different methods of secretion.
merocrine/eccrine: secretory product typically stored in membrane bound vesicles and is retrieved in exocytosis/endocytosis cycle. Most glands utilize this method.
apocrine: apical cytoplasm is released along with secretory product, ex. axillary sweat glands
holocrine: entire cell is released as part of secretory product, mitotic activity is required to replace cells, ex. sebaceous glands
141
Compare the three different types of salivary glands.
parotid- serous acini, apical regionss contain zymogen granules (deactivated enzymes), RER predominates the basal region of secretory cells
sublingual- mucus acini (PAS+), flattened nuclei at basal poles of cells (myoepithelial cells)
submandibular- both serous and mucus, serous form demilune caping mucus acini, myoepithelium
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Parenchyma vs stroma
- parenchyma are components of the gland derived from epithelium
- stroma is the connective tissue capsule surrounding the entire gland including the connective tissue partitions separating the lobes and lobules
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What is the basic structure of a multicellular gland?
lobe -> lobule (single branched gland) -> acinis (secretory component)
-these are all separated by septae or trabeculae
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What are the characteristics of acini? And why are myoepithelium important?
-secretory components of the duct and may secrete mucus, serous, or mixed
-basement membrane surrounds outer surface
-myoepithelial cells are between the basement membrane and the secretory cells
+myoepithelial cells are derived from epithelium but contain extensive actin bundles for contractility
+help the secretions into the intercalated ducts
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What are intralobular ducts? How do the two types compare?
Intralobular ducts lie within a lobule
Intercalated ducts:
- drain the seccretory acini
- lined by simple squamous epithelium transitioning to low cuboidal
- involved in bicarbonate/chloride ion exchange
Striated ducts:
- lined by cuboidal epithelium transitioning to columnar with basal striations for active transport
- actively reabsorb sodium ions; passively reabsorb chloride ions; actively secrete potassium ions -> fingerlike folds to accomodate mitochondria
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Differences between the three different types of lobular ducts.
interlobular ducts- formed by the confluence of 2+ striated ducts and are found in the septae(CT) between adjacent lobes, pseudostratified columnar
intracolumnar ducts- formed 2+ interlobular ducts, lined with columnar epithelium transitioning into stratified columnar
lobular ducts- 2+ intralobular ducts, lined with stratified columnar epithelium
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What are some characteristics of connective tissue?
- few cells
- abundant matrix
- matrix varies by amount of protein fibers
- classified on the basis of the type of matrix, fiber density, and fiber organization
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What are the functions of connective tissue?
- physically support other tissues
- binds other tissues together
- structural framework and opposes gravity
- create body contours (adipose)
- specialized tissue (blood forming and lymphoid)
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What are the types of embryonic tissue? Adult? Specialized?
Embryonic: Wharton's jelly
Adult: loose, dense, reticular, and elastic
Specialized: adipose, cartilage, bone, hematopoetic
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What is Wharton's jelly?
It is found in the embryonic umbilical cord and the pulp of developing teeth. Composed of collagen and elastic fibers, but has abundance of extracellular matrix
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What are some characteristics of loose/areolar CT?
- high ratio of fibroblasts to fibrous components
- Type I collagen fibers and elastic fibers
- found beneath epithelial tissues of most organs including tunica adventitia of blood vessels
- contains fibroblasts, mast cells, macrophages, and capillaries
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What are some characteristics of dense regular CT?
- high ratio of fibrous components to fibroblasts
- thick bundles of collagen than in loose
- highly ordered bundles of collagen separated by single rows of fibroblasts
- found in tendons and ligaments
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Characteristics of dense irregular?
- high ratio of fibrous components to fibroblasts
- thicker bundles of collagen
- no specific orientation of collagen bundles
- found in fascia, submucosa of GI tract, dermis of integument
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Characteristics of reticular CT?
- type of dense irregular with predominance of reticular fibers
- associated with lymphatic tissue
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Characteristics of elastic CT?
- type of dense irregular connective tissue with an abundance of elastic fibers which form discontinuous lamellae
- associated with walls of blood vessels (produced by smooth muscle not fibroblasts)
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Adipocytes
- derived from undifferentiated mesenchymal cells (150micrometers)
- white fat (adult) -> unilocular(single droplet of oil)
- brown fat (newborn) -> multilocular, more cytoplasm, abundant mitochondria (giving it brown coloration)
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What are the cells found in connective tissue?
fibroblasts(forms fibers and turns into fibrocyte) and fibrocytes(maintain matrix)
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What components does the matrix consist of?
- most abundant fibers are collagen fibers
- other fibers include reticular fibers and elastic fibers
- ground substance (composed of glycoproteins and glycosaminoglycans)
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What is the function of collagen I-IV? Location?
collagen I: tensile strength, general CT and bone
collagen II: tensile strength, hyaline and elastic cartilage
collagen III: reticular framework, parenchyma of organs and walls of blood vessels
collagen IV: meshwork, scaffolding, basement membranes
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How is collagen synthesized?
collagen I is synthesized as a prepropeptide
-the signal (pre-) sequence is cleaved after translocation of the polypeptide into the ER lumen of the fibroblast
-after the signal sequence is cleaved the propeptide(procollagen) molecular is secreted by the fibroblast into the extracellular matrix
the procollagen has terminal non-hilical ends that prevent polymerization
-the non-helical ends are cleaved by peptidases in order to allow polymerization to occur
-after terminal ends are cleaved, molecular is known as tropocollagen
-tropocollagen molecules spontaneously assemble into staggered arrays to form collagen fibers with a characteristic 64nm band
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What is Ehlers-Danlos syndrome?
- a group of clinically and genetically diverse group of disorders resulting from defects in the synthesis and/or structure of collagen
- abnormal collagen is devoid of tensile strength and skin is hyper-extendable and vulnerable to trauma. Joints are hypermobile.
- collagen defects extend to blood vessels and internal organs resulting in tissue rupture or detachment (ex. retina)
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The cleaving of the non helical terminal ends of procollagen converting it into tropocollagen occurs where?
a) in the RER prior to enclosure into secretory vesicles
b) cytoplasm prior to secretion
c) immediately after secretion
c
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How are elastic fibers synthesized?
- synthesized as a prepropeptide (secreted as a propeptide)
- converted to tropoelastin by extracellular enzymes and fibroblasts
- tropoelastin monomers are assembled into amorphous fibers or sheets with the aid of several types of fibrillins
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What is Marfan syndrome?
-autosomal dominant
-patients are tell with long appendages
-risk of mitral valve prolapse, so can cause heart defects
-caused by defect in gene encoding fibrillin-1, component of elastin
+composes skin, aorta, ligaments, and ciliary zonular fibers
-proteoglycans replace elastin and weaken structures
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What are glycosaminoglycans (GAGs)?
- large, negatively charged linear polymers consisting of repeated dissaccharide units
- with glycoproteins, GAGs form most of the amorphous substances of the CT
- covalently linked to protein to form proteoglycans (except hyaluronic acid)
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What are the four groups of GAGs?
- hyaluronic acid
- heparin and heparan sulfate
- chondroitin sulfate and dermatan sulfate
- keratan sulfate
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What are the characteristics of hyaluronic acid?
- largest GAG
- compose cartilage, skin, synovial fluid, and general CT
- lacks sulfate groups
- consists of repeating carb chains of N-acetylglucosamine and D-glucuronic acid
- present in nearly all CT and in vitreous body, synovial fluid, and Wharton's jelly
- binds readily with water and serves as lubricant in synovial fluids
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What are the characteristics of heparin and heparan sulfate?
- basement membrane, skin, lung, liver, blood vessels, mast cells
- repeating unit in N-acetylglucosamine and D-glucuronic acid
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What are the characteristics of chondroitin sulfate and dermatan sulfate?
- cartilage, bone, skin, blood vessels, heart valves, cornea
- most abundant of the sulfated GAGs
- repeating unit in chondroitin is N-acetylglucosamine and D-glucuronic acid
- repeating unit in dermatan sulfate N-acetylglucosamine and iduronic acid
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What are the characteristics of keratan sulfate?
- type I found in cornea
- type II found in cartilage and nucleus pulposus
- repeating unit is N-acetyleglucosamine and galactose
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What are the components and structure of a proteoglycan aggregate?
- core protein
- linker protein
- hyaluronic acid base
- GAGs
*refer to lecture for structure
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What are proteoglycans?
- secreted products of resident cells (fibroblasts, chondroblasts, osteoblasts, synovial cells, smooth muscle cells -> primitive mesenchyme)
- polyanions
- stain with conventional dyes bc of sulfate groups (hematoxylin)
- toluidin blue and crystal violet are cationic dyes that are metachromic when reacting with the anionic groups of the proteoglycans
- proteins with one or more heterosaccharide chain containing hexosamine, galactose, and other sugars
- PAS+
- high protein content and branched carb moieties
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What are three examples of glycoproteins and their characteristics?
Fibronectin
- surface protein of fibroblasts
- synthesized by epithelia and endothelia
- occurs in plasma
- occurs in alpha granules in platelets
- links cells, collagen, and glycosaminoglycans
Chondronectin
- isolated from cartilage
- promotes adhesion of mature chondrocytes to collagenous substrates
Laminin
- found in basal laminae (lamina rara)
- involved in attachment of epithelial cells to lamina propria
- noncollagenous glycoprotein
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What are the principle cell type found in CT?
fibroblasts and fibrocytes
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What are the functions of fibroblasts and fibrocytes?
- secretion and maintenance of CT matrix
- secretion of precursor fibrous molecules
- secretion of the amorphous components of the matrix (GAGs)
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What are the three resident cells found in CT?
- macrophages
- mast cells
- plasma cells
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What are some characteristics of macrophages?
- travel as monocytes in the bloodstream
- ovoid or heterochromatic nucleus
- irregular in shape with blunt processes (wandering vs fixed)
- capable of amoeboid movement
- part of mononuclear phagocytic system
- extensive Golgi, mitochondria, vesicles, and lysosomes
- may fuse with other macrophages to form large multinucleated phagocytic foreign body giant cells
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Where are macrophages found?
- in blood
- Ct (histiocytes)
- liver sinusoids (Kupffer cells)
- sinusoids of spleen, lymph nodes, bone marrow (perialveolar macrophages)
- alveoli of lungs (dust cells)
- central nervous system (microglia)
- associated with bone reabsorption (osteoclast)
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What are mast cells?
-irregularly oval in outline
-small spherical/ovoid nuclei masked by membrane bound granules
-stain with toluidine blue
-large metachromatic granules with histamine, ECF-a, SRS-a, and heparin
+ECF-A (eosinophil chemotactic factor) attracts eosinophils and neutrophils
+SRS-A (slow reacting substance of anaphylaxis) similar to histamine but has more sustained effect
+heparin from mast cells is poor anticoagulant and is probably involved in helping clear plasma liquids
-involved in hypersensitive response to allergens (edema, shock, pain, hypercoagulation, fever)
-membranes release leukotrienes
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Where are mast cells found?
- found near small blood vessels (target of histamine and SRS-A)
- absent in spleen
- found in mucosal surfaces and in CT
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What are the characteristics of plasma cells?
- activated B lymphocytes
- resemble lymphocytes but larger
- large pale nuclei with "clock face" distribution of heteochromatin (spherical and offset)
- prominent Golgi and rER
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Where are plasma cells found?
- rare in CT
- serous membranes
- lymphoid tissue
- lamina propria of gut tract
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What are the characteristics of lymphocytes?
- diameter from 6-8micrometers
- numerous in lamina propria of respiratory and GI tract
- relatively large, heterochromatic nucleus surrounded by thin rim of cytoplasm
