Histology II Flashcards
- What are the 3 types of epithelial tissues?
Contiguous cells, mucosa membrane and serous membrane
- Definition of Histology
Histology is the study of the microscopic structure of biological material and the ways in which individual components are structurally and functionally related.
- What are the characteristics of epithelium cells?
- A vascular
- Closely packed
- Have basal lamina
- What are the epithelium tissues derived from Ectoderm?
Skin, oral mucosa, glands of skin, mammary glands
- What are the epithelium tissues derived from Endoderm?
Liver, pancreas, respiratory and gastrointestinal tracts
- What are the epithelium tissues derived from Endoderm?
Liver, pancreas, respiratory and gastrointestinal tracts
- Definition of Tissue and the four main types
Tissue: collections of cells having similar morphological characteristics The four main types are: Epithelial Tissues Connective Tissue Muscular Tissues Nervous Tissues
- What composes the basement membrane?
Basal lamina -> lamina lucida + lamina densa
Lamina Retricularis
- What composes the lamina lucida?
Laminin, entactin
Laminin Receptors: integrins + dystroglcans
- What composes the lamina densa?
Collagen type 4 - anchoring
Collagen type 7 - fibrils
- What composes the lamina retricularis?
Fibroblasts, collagen 1+3
- Where can we find simple cuboidal epithelium?
Ducts of glands, Ovary covering, Kidney tubules
- Tissue preparation for TEM
- Fixation: glutaraldehyde and osmium tetraoxide
- Dehydrate and infiltration with some specific metal tissues.
- Embed and block fixed tissues in plastic.
- Cut into ultra-thin slices (50 nm thick)
- Stain sections with heavy metal salts (lead citrate and uranyl acetate) that bind nucleic acids & proteins.
- Where can we find stratified squamous epithelium?
Lining of mouth, oral pharynx, Vagina, Skin + keratinized
- Where can we find simple columnar epithelium?
Digestive tract, gall bladder, ducts
- Light microscopy description.
The light of the microscope is projected through the mirror to the condenser lens and to the specimen.
Objective lens magnifies the image of specimen (can be 4X, 10X, 40X to 100X).
The ocular lens projects to the eyes (10X).
- Magnification of Light Microscopy (formula)
Magnification = Ocular Lens x Objective Lens
- Resolution of Light microscopy
Anything smaller than 0.2 μm is out of resolution. (e.g. cellular membrane)
- Tissue preparation for light microscopy
- Stabilize cellular structures by chemical fixation.
- Dehydrate and infiltrate tissues with paraffin or plastic.
- Embed fixed tissue inside paraffin or plastic box.
- Cut into thin slices of 3-10 micrometer thick.
- Rehydrate and stain with Hematoxylin.
- Counter-stain with Eosin.
- Description of TEM (Transmission electron microscope)
The source of electrons is the cathode.
The electrons pass through the specimen and hit the bottom of the microscope, where the image viewing screen is.
- Alcian blue / Periodic acid-Schiff (PAS) Staining
- Strongly acidic mucins : blue
- Nuclei: pink, red
- Cytoplasm: pale pink
PAS detects polysaccharides as well as neutral and acidic mucins, allowing identification of hepatic glycogen, intestinal goblet cells and basal laminae.
- Where can we find trasitional epithelium?
Urinary system
- Where can we find Columnar pseudo-stratified epithelium?
Respiratory airways.
Usually contain cilia.
- What are the 3 cell surface specializations?
Brush border/microvilli, streocilia, cilia
- What composes Microvilli?
Actin, villin, fibrin, connected to the terminal web (intermediate filament) which is composed by spectin and actin
- Direct Immunofluorescence microscopy
Fluorophore is directly bound to antigen.
Fluorophore is the molecule that gives color to the signal.
- Indirect Immunofluorescence microscopy
Primary antibody recognizes the antigen and after that secondary antibody (which is marked with fluorophore) is bound to primary antibody.
- Confocal Microscopy
Resolution: 0.2 μm
Bigger clarity than light microscope.
Confocal microscopy can be used when there are 3D organs.
Specific markers can be used in order to identify specific molecules (Sox9 for stem cells).
- Golgis’ “black reaction” Staining method
- Fixation of nervous tissue blocks in potassium dichromate (2-2.5%)
- Takes 1 to 50 days or even longer
- Immersion in silver nitrate for silver chromate precipitation to fully impregnating cells in the nervous tissue
Turns most of the nervous tissue into black fibers
- Red Oil Staining
Used to demonstrate the presence of fats or lipids in fresh frozen tissue.
Performed on fresh frozen sections because fixatives containing alcohols, or routine tissue processing, will remove lipids.
- The Picro-Sirius Red Stain
Specific for collagen I and III fibers
Used in paraffin embedded tissue sections
- Haematoxylin and Eosin Staining
Haematoxylin: -Binds to basophilic substances (DNA) -Stains nuclei in blue-violet Eosin: -Binds to acidophilic substances (most proteins) -Stains cytoplasm in red or pink
- Alcian blue / Periodic acid-Schiff (PAS) Staining
Strongly acidic mucins → blue
Nuclei → pink to red
Cytoplasm → plae pink
PAS detects polysaccharides as well as neutral and acidic mucins.
- Types of cutting
Cross sectional (transverse)
Longitudinal (Horizontal)
Sagittal (Vertical)
- Functions of ECM
- Modify the morphology and functions
- Modulate survival of cells
- Regulate the migration of cells
- Direct mitotic activity
- Form functional associations with cell
- Cell Differentiation
The process by which unspecialized cells become specialized, in order to carry out specific functions.
- Stem cells definition
Cells that can proliferate without limit and can
differentiate into specialized cells.
- The three types of stem cells
Totipotent
Pluripotent
Multipotent
- Totipotent stem cells characteristics
- Arise directly from the division of the zygote.
- Can differentiate into any type of cell.
- Present in the blastocyst.
- Pluripotent stem cells characteristics
- Precursors to the fundamental tissue layers
2. Can differentiate into only one type of human tissue (epithelial, connective, muscle and nervous).
- Multipotent stem cells characteristics
- Can differentiate into different cell types in a given cell lineage.
We can say that the cells that derive from the same multipotent stem cell have the same progenitor.
- ON/OFF mechanism
In a certain cell, only some genes are expressed, while other are silent. This leads to cell differentiation.
It’s regulated by trascription factors.
- Definition of Induced Pluripotent Stem Cell (iPS)
A cell that has been reprogrammed, through TFs, to act like a pluripotent stem cell.
- Description of Yamanaka’s experiments (iPS)
- 24 possible TFs involved.
- He proved that when all of them acted
together on the DNA of a differentiated cell they were capable of taking it back to pluripotency, generating iPS. - He tested each of the 24 TFs one to see if there was a specific one responsible for this process.
- Four TFs necessary: Oct ¾, Sox2, Klf4, c-Myc.
- He had to prove that the cells he obtained were actually stem cells.
- Applications of iPS
- Regenerative medicine (in vivo)
- Toxicology (in vitro)
- Disease model, drug screening (in vitro)
- What are the three germ layers?
Ectoderm (outer)
Mesoderm (middle)
Endoderm (inner)
- Which tissues originate from the Ectoderm?
- Epidermis
- Glands on the skin
- Mouth between cheek and gums
- Some cranial bones
- Pituitary and adrenal medulla
- Nervous system
- Anus
- Which tissues originate from the Mesoderm?
- Connective tissues (proper, bones, cartilage, blood) 2. Endothelium of blood vessels
- Muscles
- Synovial and serous membranes
- Lining of body cavities and gonads
- Kidneys
- Which tissues originate from the Endoderm?
- Epithelium in the lungs
2. Part of the digestive system and part of its glands.
- Cell membrane functions
- Maintaining the structural integrity of the cell
- Selective permeability
- Regulating cell-cell interaction, recognition and communication between cells
- Interface between the cytoplasm and the external environment
- Establishing transport systems for specific molecules
- Transducing extracellular physical or chemical signals into intracellular events
- Endocytosis definition
It’s the mechanism by which the cell lets substances
inside the cell
- Phagocytosis definition
It’s a type of endocytosis that uses phagosomes, large vesicles (>250 nm).
For bigger molecules.
- Pinocytosis definition
For smaller molecules, uses vescicles of <150 nm.
These vescicles must be coated by clathrin.
- What happenes to pinocytic vescicles after their formation?
They lose the clathrin coat and fuse with endosomes.
Their content can be either degraded through lysosomes, or recycled through endosomes.
- What factor mediates pinocytosis?
EGF (epidermal growth factor)
- Cytoskeleton functions
- Shapes the cell’s form
- Controls the migration of the cells (ability of the
cells to move) - Forms an internal pathway that allows the movement of organelles within the cell.
- What are the three components of the cytoskeleton?
- Microtubules
- Thin filaments (or microfilaments)
- Intermediate filaments
- What’s in common with sweat glands, sebaceous glands and hair follicles?
Their are extended from the epidermis to the dermis
- What epigenetic regulations affect the skin?
DNM1 (DNA methyl transferase) - found more in the undifferentiated basal
Histone H3 Lysine27 trimethylation
Histone acetylation
All the processes decrease during the differentiation
- Where can we find microvilli/brush border?
Intestine, kidney proximal tubule cells
- What is the Treadmilling process in thin filaments?
- G-Actin-ATP associates with the PLUS END, where ATP is hydrolyzed to ADP.
- ADP-actin dissociates from filaments more readily than ATP-actin, so the plus end will grow faster and the minus end monomers will dissociate faster.
- This results in a net gain on the plus end, and a net loss on the minus end.
- Once a cell reaches the right size of the filament, it will put a capping protein on the plus
end, stopping the growing process.
- What composes Stereocilia?
Actin filaments, not motile
- What composes Cilia?
Anexome, made by 9 + 2 microtubules and dynein
- Where can we find cilia?
In respiratory system, oviduct
- What are the types of junctions?
Zonulae occludentes
Zonulae Adherents
Desmosomes
Hemidesmosomes
- What composes Zonulae Occludentes?
Claudius (e-cadherins), occludins, nestins, JAM
Proteins named ZO1->4
- What composes Zonulae Adherentes?
Outside: Cadheins (Ca dependent transmembrane linker)
Inside:
Vinculin, Catenin, alpha-actinin
Space diameter: 15-20 nm
- What composes Desmosomes?
Desmocollins, desmogleins connected to cadherins
Plano globing, plakophilins, held together by desmoplakin + keratin
Space diameter: 30 nm
- Where can you find compound acinar exocrine glands?
Parotid gland
Pancreas
- What are the types of secretion?
Serous, mucous, mixed
- Where can you find serous secretion?
Sweat, milk, tears, digestive juice from pancreas
- Where can you find mucous secretion?
Salivary glands + ??
- Where can you find mixed, mucous + serous secretion?
Salivary glands
- What are the methods of secretion?
Merocrine - exocytosis
Apocrine - small portion of the apical cytoplasm
Holocrine - the mature cell dies and become the secretory product
- Describe sweat glands
Simple coiled tubular
Merocrine/apocrine
Serous
- Describe Sebaceous glands
Simple branched acinar
Holocrine
Make sebum
Androgens stimulate it
If blocked + inflammation can cause acne
- Describe prostate gland
Tubuloalveolar gland lined with epithelium
Concretions can be in the center - calcified glycoproteins
Serous - citric acid,lipids, proteolytic enzymes, phosphotase, fibrinolysin
Regulated by dihydrotestosterone
- Describe salivary glands
compound tubulo/acinar
Serous from acinus
Mucous from tubular
Secrete lysozyme, lactoferrin, IgA
Covered with mayo epithelial cells
Ducts intercalated to very large principal ducts
3 glands:
- parotid: biggest, 30% of saliva, only serous
- submandibular: 60% of saliva, 95% serous 5% mucous
- sublingual: smallest, mostly mucous tubular units, coupled with Demilumes - serous cells
- What is it Metaplasia?
Changing of the type of the epithelium, pseudostratified ciliated ep. -> squamous in a smoker’s lungs (Camilla quit smoking!)
- What is the name of tumors of the epithelium?
Carcinoma/adenocarcynoma
- Describe the liver
Hepatocyte hexagon shape, classical lobes
Each lobe has single central vein
In lateral domains- bile canlicul
In sinusoidal domain-space of Disse, microvilli, lipid droplets, glycogen
Surrounded with Glisson’s capsule connective tissue- conduct of blood vessels, lymph ves., bile duct
Blood - 25% hepatic artery 75% portal vein
Bile leaves through porta hepatic
- What is the rete apparatus?
Dermal ridges (papillae) that are the interface of the epidermis and the dermis
- How is the interface of the epidermis and the dermis called?
Dermal ridges (papillae)/rete apparatus
- What is the diameter of the skin?
Thin - 0.07-0.12 micro m
Thick - 0.8 - 1.4 micro m
- What are the names of the layers of the skin?
Stratum corneum Stratum lucidum Stratum granulosum Stratum spirosum Stratum basale
- What is the name of the cells that compose the skin?
keratinocytes
- Which other cells are found in the skin?
- Langerhan cells - antigen presentation
- Merkel cells - light touch sensations mechanoreceptors
- Melanocytes
- What are the two layers of the dermis?
Papillary - form dermal ridges with epidermis, loose
Retricular layer - thick, deeper denser
- What’s the papillary layer made of?
In dermis - made of collagen 3 + elastic fibers - loose
- What’s the retricular layer made of?
Type 1 collagen - thick
- What is the superficial fascia?
Hypodermis, binded to dermis
- What’s in common with sweat glands, sebaceous glands and hair follicles?
Their are extended from the epidermis to the dermis
- What epigenetic regulations affect the skin?
DNM1 (DNA methyl tranferase) - found more in the undifferentiated basal
Histone H3 Lysine27 trimethylation
Histone acetylation
All the processes decrease during the differentiation
- Define the Plus end and the Minus end in thin filaments.
The plus end is the rapidly growing filament.
The minus end is the slowly growing filament.
The enlargment is through the Plus side.
- What is the Treadmilling process in thin filaments?
G-Actin-ATP associates with the PLUS END, where ATP is hydrolyzed to ADP.
ADP-actin dissociates from filaments more readily than ATP-actin, so the plus end will grow faster and the minus end monomers will dissociate faster.
This will result in a net gain in the plus end, and a net loss in the minus end.
Once a cell reaches the right size of the filament, it will put a capping protein on the plus
end, thus stopping the growing process.
- What is the major capping protein?
Gelsolin, once attached to the plus
end, terminates the elongation of microfilaments.
- What promote the elongation of thin filaments?
Poly-phospho-inositide, it removes the gelsolin cap, permitting elongation of the actin filament.
- What are the three types of G-actin?
- α-actin; MUSCLES
- β-actin and γ-actin : any other cell
- What proteins associate with actin?
Actin is responsible for motility via association with different actin binding protein.
The most common is myosin. Others are spectrin, fimbrin, gelsolin and talin.
- What are the 4 thin filaments arrangements?
- The Contractile Bundle (stress fibers)
- Gel-like network, elements of the cell cortex
- Filopodium, made of tight parallel bundle
- Dendritic network
- Contractile Bundle roles and characteristics
- Are associated with myosin
- The actin filaments are arranged loosely, parallel to each other, with plus and minus end alternating in direction
- Role: organelles and vesicles movements within the cells
- Endo and Exocytosis
- Gel-like network role and characteristics
- Provides the structural foundation of the cell cortex
- Contrains filamin, that assists in the formation of the actin network and gives stiffness to the network
- Parallele bundles role and characteristics
2 proteins: Fimbrin (in tiny spikes) and Villlin
- Fimbrin allows movement
- VIllin forms the microvilli
- How are cells able to move?
Thanks to the lamellopodia: this extracellular protrusion
enables cancer cell to invade the surrounding tissues.
When we remove one of the proteins that binds to the filaments, the cells can’t move and we’ll have filopodia.
- What is the focal region?
It’s a zone of connection between the cell and the extracellular matrix.
It’s an anchoring junction of the cell to a non-cellular substrate.
- How do cells mantain attachment?
Bundles of the actin cytoskeleton attach to the transmembrane linkers integrins, that in turn bind glycoproteins such as fibronectin in the ECM, permitting attachment.
- How does focal contact work?
The intracellular region of the focal region (integrins) will bind to talin (in cytoskeleton), that will bind the actin and vinculin.
They will combine to form contractile bundles, known as stress fibers.
- How big are intermediate filaments?
8-10 nm
- Functions of intermediate filaments
- Provide structural support for the cell
- Form a deformable 3D structural framework for the cell
- Anchor the nucleus in place, forming a ring around it.
- Provide an adaptable connection between the cell membrane and the cytoskeleton
- Maintenance of the nuclear envelope as well as its reorganization subsequent to mitosis.
- Structure of intermediate filaments
The intermediate filaments are structured in a rope-like motif, coiled one onto the other.
They are formed by fibrous subunities.
Each monomer has an N-terminus (head) and C-terminus (tail), both folded into globular domains.
- Categories of intermediate filaments
- Keratins: specific for epithelial cells
- Desmin: specific of all type of muscle cells
- Vimentin: specific of cells of mesenchymal origin, fibroblast and endothelial cells
- Neurofilaments nuclear lamins : specific of neurons
- What are microtubules?
They’re long, straight and rigid cylindrical structures with a diameter of 25nm.
They’re hollow inside.
- Functions of microtubules
- Provide rigidity and maintain cell shape
- Regulate intracellular movement of organelles and vesicles
- Establish intracellular compartments
- Allow movement of ciclia and flagella.
- Formation of mitotic spindle.
- What are the 3 monomers of tubulin?
α-tubulin, β-tubulin and γ-tubulin
- How are the tubulin monomers organized?
They are scattered all over the cell and are usually packed together, forming heterodimers.
They are polarized molecules, with a Plus end (beta tub) and a Minus end (alpha tub).
- What is the centrosome?
It’s the region where the γ-tubulin ring complex begins the nucleation process.
It’s considered the microtubules organizing center (MTOC) of the cell, located near the nucleus and extend towards the cell periphery.
- What are the functions of cilia?
They move waste materials through their rhythmic movement and constant beating
- Where are cilia found?
- epithelial cells in the airway
- female fallopian tubes
- Where is the flagellum found in humans and what’s its function?
The only flagellated cell in humans is the sperm cell
Its main function is cellular locomotion, so that it can move towards the female egg cells.
- What’s NAV3 (Navigator -3)?
It’s a cap protein that localizes on the plus ends of microtubules and enhances their polarized growth. Also increases the ability of cells to adhere to a migration course and usually slows down migration rates.
- What happens if NAV3 is lost?
Development of breast cancer metastasis.
- How can we see the elongation of microtubules?
By marking NAV3 with GFP: coexpression of GFP-NAV3 and mCherry- α-tubulin.
With this experiment it’s possible to demonstrate that NAV3 protein is localized at the tips of the growing MT and that elongation goes through the plus ends.
- What are centrioles?
They’re small, cylindrical structures with a fixed diameter of 0.2 μm and a length of 0.5 μm.
They’re paired structures, arranged with a perpendicular angle.
- Structure of centrioles
A single centriole is composed of nine triples of microtubules, arranged around a central axis (forming an empty cylinder).
Each triplet forms an oblique angle with the adjacent and a perpendicular angle with the fifth triplet (orthogonal orientation).
- How do centrioles mantain their shape?
They’re embedded in a matrix of pericentriolar material: γ-tubulin and pericentrin, both interacting with several microtubules that anchor them to the centrosome.
- What is the structure of exocrine glands?
Lobes -> lobules -> Parenchyma -> Secretary acini
Surrounded by connective tissue made of septa
Have duct and a secretory portion
- What are the types of stimulation?
Autocrine
Paracrine
Endocrine
- How to classify exocrine glands?
- Number of cells: unicellular/multicellular
- Secretory portion: acinar/tubular/alveolar
- Number of ducts: simple/compound
- Type of secretion: serous, mucous, mixed
- Methods of secretion: merocrine, apocrine, holocrine
- Describe Goblet cell
- unicellilar, goblet shape
- his apical side is techa, contain secretory droplets
- release mucigen by exocytosis
- stimulated by chemical irritation + parasympathetic innervation
- Where can you find simple tubular exocrine glands?
Lining of intestine, secrete mucous
- Where can you find simple coiled tubular exocrine glands?
Sweat glands
- Where can you find simple branched tubular exocrine glands?
Gastric clands
- Where can you find simple branched acinar/alveolar exocrine glands?
Sebaceus glands
- Where can you find compound tubular/acinar or tubular/alveolar exocrine glands?
Mammary glands
Prostate gland
Salivary gland
- Where can you find compound acinar exocrine glands?
Parotid gland
Pancreas
- What are the types of secretion?
Serous, mucous, mixed
- Where can you find serous secretion?
Sweat, milk, tears, digestive juice from pancreas
- Where can you find mucous secretion?
Salivary glands + goblet
- Where can you find, mixed, mucous + serous secretion?
Salivary glands
- What are the methods of secretion?
Merocrine - exocytosis
Apocrine - small portion of the apical cytoplasm
Holocrine - the mature cell dies and become the secretory product
- Describe sweat glands
Simple coiled tubular
Merocrine
Serous
- Describe Sebaceous glands
Simple branched acinar
Holocrine
Make sebum
Androgens stimulate it
If blocked + inflammation can cause acne
- Describe prostate gland
Compound Tubuloalveolar gland lined with epithelium
Concretions can be in the center - calcified glycoproteins
Serous - citric acid,lipids, proteolytic enzymes, phosphotase, fibrinolysin
Regulated by dihydrotestosterone
- Describe the exocrine pancreas
Compound Acini with centroacinar cells in luman (beginning of the duct)
Secretion can be enzyme rich/poor
Secrete - amylase, lipase, deoxy/ribonuclease, cholesterol estarase,
Proenzymes: chymotrypsinogen, procarboxypeptidase, elastase
Centroacinar cells
Low coboidal
- secrete bicarbonate in response to secretin (by DNES in small intestine) + acetylcholine (by parasympathetic)
- Describe mammary glands
Compound tubulo/alveolar gland
Apocrine- lipids Merocrine- Proteins
Milk= proteins, lipids, lactose, lymphocytes, monocytes, antibodies, minerals, fat solvable vitamins
Lactiferous duct -> sinus
- Pregnancy, Estrogen+progesterone, glandular parenchyma with colostrum
- After birth, prolactin -> milk
- Describe the liver
Hepatocyte hexagon shape, classical lobes
Each lobe has single central vein
In lateral domains- bile canlicul
In sinusoidal domain-space of Disse, microvilli, lipid droplets, glycogen
Surrounded with Glisson’s capsule connective tissue- conduct of blood vessels, lymph ves., bile duct
Blood - 25% hepatic artery 75% portal vein
Bile leaves through porta hepatic
- Which types of endocrine glands exist?
Cord of cells/follicles
Polypeptide/lipid hormones
- What is it intracrine activity?
When hormone act inside the cell regulating intracellular events like growth.
Steroids
- What section of cells are found in the pituitary gland?
Adenohypophesis - anterior
Neurohypophesis - posterior
Parsintermedia - space between them, cords of 1 cell type
- What is the origin of the adenohypophesis?
Oral ectoderm - Rathke pouch, controlled by BMP4, FGF8, WNT8
- What is the origin of the neurohypophesis?
Neural ectoderm, secretory neurons
- What are the cells that compose the Adenohypophesis?
Acidophils - most abundant, large, colored with orange red in their granules
Basophils - colored with blue color
- What are the hormones that produced by the acidophils and what do they secrete?
Somatotrophs - somatotropin/GH
- stimulated by SRH
- inhibited by somatostatin
- increase metabolism
- induce liver to produce ILGF1+2->mitosis in epiphyseal plate
Mammotrophs - prolactin
- mammary gland development
- lactation
- What are the hormones secreted by the basophils?
ACTH - on adrenal cortex
TSH - Thyroid
FSH - spermatogenesis, follicular development + estrogen
LH - Androgen secretion, ovulation + progesterone
- What does the neurohypophesis secrete?
ADH, Oxytocin
- Where are the hormones of the neurohypophesis made?
In the neurons soma that is found in the paraventricular/supraopt nuclei in the hypothalamus
- What are the secretion of hypothalamus and their induced hormones ?
TRH - TSH CRH - ACTH SRH - GH GnRH - LH/FSH PRH - Prolactin PIF - Prolactin Inhibitor Factor
- Describe the structure of the thyroid gland
2 lobes connected by the isthmus
Have follicles 0.2-0.9mm diameter
Connective tissue septa forms a capsule which invades the parenchyma containing lymphatic+blood vessels, nerve fibers
- What are the cells that compose the thyroid gland?
Follicular cells
Parafollicular cells
- Describe the follicular cells
Release T3,T4
Hormones stored bound to thyroglobulin within colloid
Apicali located lysosomes and microvilli
After TSH binding -> cell develops filopodia -> endocytosis
- Describe the parafollicular cells
Release calcitonin - inhibits bone resorption byo steoclasts, less Ca in blood more in bones
The cells are bigger and found between the follicular cells
- What do the follicular cells in the thyroid gland release?
T3 thyroxin - 1 day half life
T4 triiodothyronine- 6 days
Controlled by TSH from adenohypophysis
- Describe thyroid gland feedback mechanism
TRH -+-> TSH -+-> T3/4
T3/4 -> TSH + TRH
- Describe the parathyroid gland
4 glands found in the posterior surface of thyroid gland
Contains chief cells and oxyphil cells
- What are the chief cells?
Found in the parathyroid
The functional parenchyma cells
Eosinophilic Stained
Contain PTH
- What is PTH?
Parathyroid hormone releases by chief cells.
Works on bone, kidney, intestine
Increase Ca in blood and interstitial fluid (8.5-10.5mg/dL), when low induces secretion of PTH
- Bone, osteoblasts increase secretion of osteoclasts stimulating factor
- kidney, less Ca loss in urine, produce alcitirol-active vit. D
- intestine, Vit, D is needed for Ca uptake
- What is oxyphil cell?
Found in the parathyroid gland
Might be an intermediate cell, inactive chief cell
Deeply stained with eosin
- What are the layers of the adrenal cortex?
Zona Glomerula
Zona Fasciculata
Zona Reticularis
- What is secreted from the Zona Glomerula, by which stimulus and how the cells look?
Columnar cells closely packed
Aldosterone, deoxycorticosterone
When stimulated by ACTH and andiotensin2
- What is secreted from the Zona Fasciculata , by which stimulus and how the cells look?
Straight cords, 1-2 thick layers, cells are called spongiocytes
Secrete cortisol + corticosterone
Stimulated by ACTH
- What is secreted from the Zona Reticularis , by which stimulus and how the cells look?
Irregular cords that form an anastomosing network
Dehydroepiandrosterone, androsterone
Stimulated by ACTH
- What are the two types of muscle tissue?
Striated and smooth
- General Characteristics of skeletal muscle
- Striated
- Composed by long cylindrical multinucleated cells with peripherally placed nuclei.
- Voluntary, quick and vigorous contractions
- Used for locomotion, mastication and phonation
- General characteristics of cardiac muscle
- Striated
- Composed by elongated branched cells with single central nucleus
- Intercalated discs at the ends
- Involuntary, vigorous and rhythmic contractions
- General characteristics of smooth muscle
- Non-striated - irregularly arranged contractile machinery
- Fusiform cells with central nucleus
- Involuntary, slow and long lasting contractions
- What creates striations?
They depend on the presence or absence of a regularly repeated arrangement of myofibrillar contractile protein (myofilaments).
- How do skeletal muscles regenerate?
They increase size (hypertrophy) and number (proliferation)
Satellite cells are the source of regenerative cells
- How do cardiac muscles regenerate?
Hypetrophy
Small regenerative capacity in cardiomyocytes
- How do smooth muscle regenerate?
Hypetrophy and proliferation
Vascular pericyte are the main source of smooth muscle regeneration
- Functions of muscle tissue
- Movement
- Posture maintenance
- Joints stabilization
- Thermogenesis
- What’s Cachexia?
It’s a phenomenon that leads to atrophy of muscle tissue. Some consequences are weight loss, muscle atrophy, fatigue and weakness
- Properties of muscle tissue
- Excitability: response to chemical signals of nerve cells and generate electrical signals
- Elasticity: able to return to original shape
- Extensibility: able to stretch
- Contractility: able to shorten and generate force
- What’s the Endomysium?
Connective tissue that surrounds the sarcolemma directly, also called reticular fibers
- What’s the perimysium?
Connective tissue that surrounds the fascicle and derives from the endomysium
- What’s the Epimysium?
Connective tissue that surrounds the whole muscle, most dense.
- Composition of skeletal muscle
It’s composed of longitudinal arrays of cylindrical myofibrils (1 or 2 micrometer each) extended to the entire length of the cells and are precisely aligned, being responsible for the striation and the characteristic light and dark banding
Cells are multinucleated with peripherally located nuclei
- What are T tubules?
They are tubular invaginations in the sarcolemma.
They are flanked by two terminal cisternae composing a triad
- What are terminal cisternae?
They are responsible for the Ca++ storage, present in the sarcoplasmic reticulum
- Where are blood vessels found in the skeletal muscle?
Between the fascicles, the perimysium level
- What’s the main function of the sarcomere?
It’s responsible for the contraction and relaxation of muscle fibers though the overlapping of thick and thin filaments
- What is the sarcomere composed of?
- Thick filaments are composed of type II myosin. Paralleled, organized between the thin filaments.
- Thin filaments are composed primarily of F-actin, but also tropomyosin, tropomodulin and troponin.
- Subdivision of the sarcomere
- Two halves of I bands: light bands
- A band: dark bands
- H band: pale area in the center of the A band
- M line: found in the middle of the H band
- Z disk: found in the middle of the I band
- What are other structural proteins found in the sarcomere?
- Titin - holds the thick filaments in place
- Nebulin - surrounds the thin filaments holding it in place
- Desmin and Vimentin - give strength to the Z line
- What’s Huxley’s sliding filament theory?
- In the relaxed state: the thick filaments do not extend the entire length of the sarcomere, leaving some regions with only thin filaments
- During contraction the myofilaments do not shorten. Instead, thin filaments slide over the thick filaments.
I band becomes narrower, H bands are extinguished, Z disks move together, while the A bands remain unchanged
- Muscle contraction
- An impulse is generated along the sarcolemma and transmitted through T tubules to
the terminal cisternae. - Ca++ leaves the terminal cisternae and binds to troponin, altering its conformation.
This shifts the position of tropomyosin deeper into the groove, exposing the myosin binding site on actin. - In the resting state, free ATP is bound to myosin.
- ATP hydrolysis: conformational change of myosin head. Both ADP and Pi remain attached to myosin. The entire complex binds weakly to actin, now exposed.
- Release of Pi: induces stronger binding and trigger power stroke: thin filament is dragged toward the center of the sarcomere.
- New ATP molecules binds to myosin, causing the bond between myosin and actin to break.
- The cycle must be repeated several times for contraction to happen.
- What is the neuromuscular junction-motor end plate composed of?
- axon terminal
- synaptic cleft
- muscle cell membrane
- What’s the main function of the neuromuscular junction?
It’s to transmit a stimulus from the nerve fiber
to the muscle fiber.
- How is the stimulus transmitted?
- A stimulus arrives and depolarizes the axon
terminal. This triggers the opening of voltage-gated calcium channels. - Release of calcium induces the release of the
synaptic vesicles that fuse with the membrane to
release Acetylcholine in the synaptic cleft. - Acetylcholine binds to acetylcholine receptors
in the muscle cell membrane. - Ligand-gated channels open, leading to depolarization of the sarcolemma and generation of an action potential.
- The impulse generated spreads quickly through the muscle fiber thanks to the system of T tubules, initiating muscle contraction.
- How is acetylcholine degraded?
Acetylcholinesterase degrades acetylcholine into acetate and choline.
Choline is transported back into the axon terminal by a sodium-choline symport and is recycled.
- How is acetylcholine synthesized?
Acetylcholine is synthesized again from recycled choline and acetate by Choline acetyltransferase
- What’s Rigor Mortis?
RIgor Mortis is a state of muscularity rigidity that begins 3-4 hours after death and lasts for 24-36 hours.
- What causes Rigor Mortis?
After death, Ca2+ ions leak out of the sarcoplasmic reticulum and allow myosin heads to bind actin
Since ATP synthesis has ceased, it cannot detach myosin, causing the muscle to stay contracted.
- Characteristics of Cardiac muscle tissue
- Striated
- Self-excitatory and electrically coupled.
- Composed of branched fibers with intercalated disks.
- Numerous mitochondria.
- Sarcoplasmic reticulum and T-tubules are in
dyads at the Z line: no terminal cisternae.
Also the T-tubules are two times larger in
diameter than the ones in skeletal muscle.1
- How is cardiac muscle tissue vascolarized?
This tissue is highly vascularized, with capillaries around every cardiac muscle cell.
- How is the myocardium composed?
The myocardium consists of an anastomosing network of branching cardiac cmuscle cells arranged in layers (laminae).
Laminae are separated by connective tissue.
- How are intercalated disks composed?
They have to portions:
- Transverse portions: fasciae adherentes and desmosomes. Thin myofilaments attach to the fascia adherentes.
- Lateral portions: gap junctions. They permit the rapid flow of informations from one cell to the other.
- What’s the structure of cardiac sarcomere?
- Nebulin extends up to 20% of the length of thin filaments
- T- tubule as diad located on the Z-line
- No terminal cisternae
- Negatively charged external lamina storage of calcium
- How is calcium stored in cardiac muscle tissue?
Because there are no cisternae to store the calcium, there are additional sources available.
Extracellular Calcium can flow through the T-tubules and enter the cardiac cells at te time of depolarization. Also the external lamina coating the T-tubules contains calcium for instantaneous release.
- Where is smooth muscle found?
Found in blood vessels, GI and urogenital
organ walls, dermis of the skin.
- Features of smooth muscle
- Neither striations, nor a system of T-tubules.
- Involuntary muscle tissue
- Regulated by the autonomic nervous system and
local physiological conditions. - Smooth muscle cells are fusiform and elongated, with a central portion containing an oval nucleus.
- What are the two types of smooth muscle?
- Cells of multiunit smooth muscle: they can contract independently of one another because each cell is
connected to a nerve. - Cell membranes of unitary smooth muscle: they form gap junctions with contiguous smooth muscle cells, sharing nerve fibers. They contract along with
neighbouring cells.
- What can smooth muscle cells do?
Some cells are capable of exogenous protein synthesis.
They also produce collagen, elastin, GAG, proteoglycans and growth factors.
- How are fibers stimulated in cardiac smooth muscle?
Fibers are stimulated by neurotransmitters (ACh), hormones (norepinephrine ) or autorhythmic signals
- How is action potential trasmitted?
Through gap junctions.
- What composes the adrenal medulla?
Chromatin cells
-Polyhedral parenchyma cells arranged in cords and supported by reticular fibers
- What the adrenal medulla secretes?
Epinephrine, norepinephrine
stimulated by postganglionic sympathetic splanchnic nerves
- Describe the islets of Langherans
Rounded 3000 cells distributed in the pancreas
0.3 mm diameter, surrounded by reticular fibers
Composed of five different cells
- What are the cells that compose the islets of Langherans and what do they secrete and what do they do?
Beta cells - insulin + amylin (inhibit gastric emptying and alpha cells)
Alpha cells - glucagon
Delta cells - somatostatin (inhibit pancreas exo/endocrine release) + vascactive intestinal peptide - regulates smooth muscle tonus, glycogenesis)
PP cells - pancreatic polypeptide (exocrine)
G cells - gastric (raise GCl in ctomach)
- Describe the leydig cells
Interstitial cells, dispersed into loose connective tissue housing fibroblasts and mast cells
Adjacent to the seminiferous tubules in the testicle
Secrete testosterone and INSL3
Stimulated by LH
- What are the hormones secreted by Leydig cells and what is their role?
Testosterone - spermatogenesis
INLS3 - descent of testicles into scrotum in fetal life
- From which embryonic layer does the nervous tissue come from?
Ectoderm, in particular neural crest cells.
- What are the 2 classes of cells in nervous tissue?
- Neurons: Proper cells, in charge of the communication.
2. Neuroglia: Non-neuronal cells of the nervous system.
- What are the functions of neuroglia cells?
They provide physical and metabolic
support, they respond to injury, and participate in the composition of the blood brain barrier.
- What are the 2 components of nervous tissue?
- Central Nervous System(CNS): Composed by the brain, spinal cord and meninges.
- Peripheral Nervous System(PNS): It includes the nervous system outside the brain and spinal
cord.
- What are the 3 parts of a neuron?
Cell body (soma)
Dendrites
Axon
- What are Nissl bodies?
Clumps of basophilic material in RER of soma
- Characteristics of soma.
- Large central nucleus, rich in euchromatin
- Lots of Polyribosomes
- Cytoplasm mostly occupied by RER
- Describe Dendrites.
- Projections (cell processes) that depart from the soma.
- They receive stimuli from other neurons.
- Multibranched structure, allows the cell to receive multiple stimuli from many neurons simultaneously.
- Axon characteristics
- Long process that conducts the stimulus
from the soma to the axon terminals (end bulbs ) - Approach other other dendrites to form a synapse
- Axon hillock are the processes which will give rise to the axon
- Propagagate action potential
- What are the three types of neurons?
Multipolar, bipolar, pseudounipolar
- What are the characteristics of Multipolar neurons?
- Most common ones,
- Single axon and two or more dendrites.
- Presence of several processes.
An example can be the motor neurons.
- What are the characteristics of Bipolar neurons?
- Two processes, one giving rise to the axon and the other to the dendrites.
- Rare, and is mainly present in specialized sensorial tissue (such as the retina, olfactory epithelium, inner ear).
- What are the characteristics of Pseudounipolar neurons?
- Really rare,
- Characterized by a single process arising from the cell body, that splits into two branches, one becoming the axon and the other becoming the dendrites.
- What’s the functional classification of neurons?
Motor Neuron
Interneurons
Sensory Neurons
- What are the characteristics of Motor neurons?
- Also called efferent fibers
- Convey impulses from the CNS to the
effector cells. - They can be subdivided in somatic efferent neurons and viscered efferent neurons.
- Their morphology is generally multipolar.
- What are the characteristics of Interneurons?
- Also called intercalated neurons.
- All the neurons that are not motor nor sensitive.
- Connect two brain regions, and form brain circuits. 4. Their morphology is usually unipolar.
- What are the characteristics of Sensory neurons?
- Convey impulses from the periphery to the CNS.
- Have receptors that can transduce a physical signal (light, pressure, heat) into a chemical one (through synapses).
- Either bipolar or pseudounipolar.
- What are the cell types of neuroglia?
CNS: Astrocytes, Oligodendrocytes, Microglial cells, Ependymal cells(ependymocytes),
PNS: Schwann cells, Satellite glial cells
- What are the functions of Astrocytes?
- Anchor neurons to their nutrients supply blood vessels - guide migration of young neurons.
- Form a blood-brain barrier
- Recruited to damaged areas of the CNS, where they form cellular scar tissue (glial scar)
- Provide structural and metabolic support to neurons acting as scavengers of ions
- What are the characteristics of Astrocytes?
- Largest of the neuroglial cells
- Originate from the neural tubeùù
- Intermediate filaments in the cytoplasmic bundles are composed of glial fibrillar acidic protein (GFAP).
- What are the two types of Astrocytes?
- Protoplasmic Astrocytes: found in the gray matter of the brain
- have tips called pedicels which come in contact with the blood vessels.
- contact with the pia matter forming the pia-glial membrane.
- regulate the flow of CSF. - Fibrous Astrocytes: found in the white matter of the brain
- associated with pia matter and blood vessels but are seperated from these by their own basal lamina.
- What are the characteristics of Olygodendrocytes?
- Originate from the neural tube
- Myelin sheath production for CNS
- Located both in white and gray matter
- Devided in interfascicular and satellite
oligodendrocytes.
-Satellite oligodendrocytes are for of large neurons. - The oligodendrocytes in the grey substance of the cortex do not produce myelin but act locally as
supporting cells
- What are the characteristics of Schwann cells?
- Surround fibers of the PNS
- Originate from the neural crest
- Produce the myelin sheath guiding the regrowth of PNS axons
- A single Schwann cell can myelinate only one axon, several unmyelinated axons may be enveloped by a single Schwann cell.
- What are the characteristics of Microglial cells?
- Monocytes originating from the bone-marrow
- Clear debris and damaged structures in the CNS
- Protect against viruses, microorganisms and
tumor formation by secreting γ-interferon. - Recruit T lymphocytes and interact with
complement-associated proteins C1q and C3 destroying synapses.
- What are the characteristics of Ependymal cells?
- Epithelial-like lining of ventricles in the brain (choroid plexus) and the central canal of the spinal cord,
- Originate from neural tube.
- Some of them have motile cilia (secondary)
- What are the characteristics of Satellite glial cells?
- Cuboidal cells in the PNS
- Originate from the neural crest
- Surround neuron cell bodies in ganglia
- Regulate O2, CO2, nutrient, neurotransmitter levels around neurons in ganglia.
- What is myelin composed of?
It’s composed of multiple concentric layers of glial plasma membrane (lipids, proteins and
water) of oligodendrocytes in the CNS, Schwann cells in the PNS
It’s wrapped around axons, insulating them and increasing the rate at which action potentials are propagated along the axon.
- What are the nodes of Ranvier?
They are interruptions that occur in the myelin sheath at regular intervals.
They are rich in voltage-gated Na+ ion channels permitting saltatory conduction
- What distiguish White matter of Gray matter?
White matter: contains myelinated axons.
Gray matter: consists of neuronal cell bodies, dendrites and unmyelinated axons.
- When are neurons myelinated?
The myelination dependend on their function
Motor nerves are nearly completely myelinated at birth
Sensory roots are not myelinated for several months
- What are the four types of synapses?
- Axo-dendritic: between an axon and a dendrite
- Axo-somatic: between an axon and a soma
- Axo-axonic: between two axons
- Dendro-dendritic: between two dendrites
- What does the cytoplasm at the presynaptic membrane contain?
It contains mitochondria, a few elements of smooth
endoplasmic reticulum, and an abundance of synaptic vesicles assembled around the presynaptic
membrane.
- What are synaptic vescicles?
Synaptic vesicles are spherical structures (40 to 60 nm in diameter) filled with neurotransmitter
substance
Manufactured and packaged near the axon terminal.
- What do anterograde transport and retrograde transport carrt?
Anterograde: Actin, myosin, clathrin, enzymes for neurotransmitter synthesis are transported from the body to the axon terminal
Retrograde: proteins for neurofilaments, subunits of microtubules, material taken by endocytosis(viruses, toxins) and other proteins destined for degradation. To the lysosomes of the soma
- What are the enzymes in axoplasm?
- CAMs: associated with synaptic vesicles, forming the active site of the synapse
- Synapsin-I: assists in the movement of the vesicles and the release of neurotransmitters
- Synapsin-II: responsible for the docking of the vesicles
- SNARE: help with fusion of the synaptic vesicles with the pre-synaptic membrane
- Synaptotagmin and AP-2: help in clathrin-mediated endocytosis to recaptur excess membrane
- What does the neurotransmitter in post-synaptic membrane initiate?
Depolarization (excitatory response) or hyperpolarization (inhibitory response)
- What are peripheral nerves?
Peripheral nerves are bundles of nerve fibers (axons) surrounded by several investments of
connective tissue sheaths.
- What are the connective tissue investments of peripheral nerves?
Perineurium
Epineurium
Endoneurium
- What’s the perinerium?
The middle layer of connective tissue investments.
It is composed of dense connective tissue
Its inner surface is lined by several layers of
epithelioid cells joined by zonulae occludentes and surrounded by a basal lamina.
- What’s the Epinerium?
Outer layer of dense irregular collagenous connective tissue
- What’s the Endonerium?
The innermost layer of the three connective tissue investments of a nerve,
surrounding individual nerve fibers (axons).
- What does the Autonomic Nervous System do?
- Provide motor innervation to smooth muscle
and cardiac muscle - Supply secretomotor innervation to glands
- What are the 2 parts of autonimc nervous system?
- Sympathetic nervous system
2. Parasympathetic nervous system
- What does the sympathetic nervous system do?
Fight or Flight response :increases respiration, blood pressure, heart rate, and blood flow to the skeletal muscles, dilating pupils of the eye, and generally slowing down visceral function.
- What does the parasympathetic nervous system do?
Homeostasis: decreases respiration, blood pressure, and heart rate, reduces blood flow to skeletal muscles, constricts the pupils, and generally increases the actions and functions of the visceral system.
