Week 5 Flashcards
What are the three germ layers in the embryo and what parts of the body do they give rise to?
- Endoderm: visceral organs
- Mesoderm: connective tissue and muscles (mesenchyme)
- Ectoderm: epidermis and neural tissue
What are the seven types of connective tissue?
- muscle tissue
- nerve tissue
- bone/cartilage tissue
- hematopoietic cells
- vascular tissue
- fibrous tissue
- adipose tissue.
What is the major cell of connective tissue and what is its function?
- Major cell is the fibroblast
- Function: synthesizes ECM/proteins (collagen/reticular fibers/elastic fibers)
What are the two main subtypes of connective tissue?
- Name subtypes of these subytypes if any
Loose and Dense (Regular & Irregular)
What is the purpose and location of loose connective tissue?
- Purpose - anchoring, support, source of cells
- Location:
- Underneath epithelium
- Site of initial attack by bacteria - but will be destroyed by immune cells (i.e. mammary gland, gut epithelium) → swelling/edema
What is the composition of loose connective tissue?
- Composition
- Loosely arranged fibers that are irregular/disorganized
- Sparse collagen fibers
- Abundant ground substance
- Abundant cells (immune cells)
What is the purpose and composition of regular dense connective tissue?
- Purpose - strength
- Composition
- Collagen fibers in parallel array and densely packed
What are the three main locations of regular dense connective tissue fibers?
- Tendon (muscle to bone)
- Ligaments (bone to bone)
- Aponeuroses (muscle to muscle)
What is the purpose and composition or irregular dense connective tissue fibers?
- Purpose - resists stretching and distension (skin dermis/colon)
- Composition
- Mostly collagen fibers that are irregular (random orientation)
- Sparse amounts of cells, mostly fibroblasts
What is the purpose of the collagen fibers?
Allow for flexiblity with tensile strength
What is the composition of collagen fibers and what is the hierarchy of the structure?
- Composition: procollagen (triple helix - 3 alpha chains) → collagen molecule (tropocollagen) → fibril → fibers
Of reticular fibers, what is the:
- purpose
- location
- composition (what type of collagen)
- synthesizing cell
- Purpose: provide supportive framework for cells
- Location: supporting stroma in lymph nodes, spleen
- Composition: Type III Collagen fibers, mesh-like arrangement (like a cage)
- Synthesis: by fibroblast mostly
Of elastic fibers, what is the:
- purpose
- location
- composition (what type of collagen)
- synthesizing cell(s)
- Purpose: allows tissue to stretch/distend, but return to original shape
- Location: major part of vertebral ligaments, elastic arteries, larynx)
- Composition: branching network
- Central core of elastin
- Surrounded by fibrillin microfibril - organizes elastin
- Random coiling → elasticity
- Synthesis: fibroblasts and smooth muscle cells
What is the extracellular matrix?
What three things does it contain?
- Extracellular Matrix
- Network that supports and surrounds cells within connective tissue
- Contains: collagen, elastic fibers, ground substance (makes up a big component)
What is the description and composition of ground substance?
- Description: watery substances that allow for the diffusion of oxygen/nutrients from vasculature to cells
- Composition:
- Proteoglycans
- Glycosaminoglycans (GAGs) attached to core protein
- Multi-adhesive glycoproteins - serve as attachment points within ground substance
What are the two types of connective tissue cells?
- Resident Cell Population (permanent, non-migratory)
- Wandering and Transient Cell Population (predominantly cells from the blood)
What are the 5 types of resident cell populations?
- Fibroblast – main cell of connective tissue; makes collagen etc.
- Macrophages (Tissue histiocyte) – phagocytic cell
- Adipose Cells
- Mast cells
- Undifferentiated Mesenchymal Cells
What are the types of wandering and transient cell populations?
- Wandering and Transient Cell Population – predominantly cells from blood
- Lymphocytes
- Plasma Cells
- Neutrophils (PMN’s)
- Eosinophils
- Basophils
- Monocytes
What are the types of collagenopathies (diseases of collagen)
- Osteogenesis Imperfecta
- Ehlers-Danlos Syndrome
How does osteogenesis imperfecta occur and what is it a defect in (what subtype specifically)?
- Inheritable defect (most common autosomal dominant) of collagen Type I
- Defect in quantity AND quality of collagen
- Bone is most affected (90% of bone is Type I collagen)
- Mutations in genes that code for a-1 and a-2 chains of collagen molecules
What are the symptoms associated with osteogenesis imperfecta?
- Soft, thin, brittle, deformed bones - because of ineffective bone formation
- Collagen forms abnormally (not parallel)
- Very prone to repeated fractures with ineffectual healing
- Blue sclera
How does Ehlers-Danlos Syndrome occur and what is it a defect in (what subtype specifically)?
- Defect:
- Collagen Type III
- mutation in lysyl hydroxylase → abnormal cross-linking of collagen fibers
What tissues are most affected in Ehlers-Danlos Syndrome?
- Tissues rich in collagen, such as skin and hollow organs (GI and blood vessels) are most affected
- Tissues lack tensile strength → hyperextensile skin, hypermobile joints
- joint dislocation
- Skin is stretchable, fragile, prone to trauma,
- Internal organs → rupture (GI, great vessels)
- Rupture of cornea and retinal detachment
- Tissues lack tensile strength → hyperextensile skin, hypermobile joints
What are the two disorders of elastic fibers?
- Marfan’s Syndrome
- Solar Elastosis of Skin
Where does the defect lie in Marfan’s Syndrome?
What function does this defect affect and where is this protein abundant in?
- Inherited defect in Fibrillin1 (glycoprotein)
- Fibrillin1 is the scaffolding upon which tropoelastin is deposited to form elastic fibers
- Particularly abundant in aorta, ligaments, and lens
- Aortic Rupture
- Particularly abundant in aorta, ligaments, and lens
What causes solar elastosis of the skin and where do the defects lie?
- Repeated exposure to ultraviolet radiation → premature aging (wrinkling, solar elastosis, irregular pigmentation)
- UV radiation → degradation of collagen and remodeling of fibrillin microfibrils → truncated → nonfunctional elastic fibers → decreased skin elasticity
- Seen as irregular fibers and bluish discoloration in dermis
How/Why does a keloid occur?
- Hypertrophic scar, due to excessive collagen accumulation in response to injury
- Does not regress on its own but extends beyond boundary of injury
What did Griffith’s experiement achieve?
Dicovered the transformation of pathogenic pneumococcal S-bacteria strain to non-pathogenic R-bacteria to kill rats
What did Avery’s experiement achieve?
Continuation of Griffith’s experiment; Digestion of different macromolecule → proved DNA was the transforming principle
What did Watson and Crick’s experiment achieve?
Discovered the basic DNA structure and base pairs
What does replication mean (in regards to DNA)?
Replication: transmission of likeness of DNA
What does information flow mean (in terms of DNA)?
- Information Flow: DNA provides means for production of all of the cell’s proteins
What is mutability (in terms of DNA)?
- Mutability: heritable changes in cellular properties
What part of DNA is considered the primary structure? What makes up each of these parts?
- Mononucleotide Structure
- Base – purines/pyrimidines
- i.e. Adenine
- Nucleoside – base + sugar (via N-glycosyl linkage)
- i.e. adenosine
- Nucleotides – base + sugar + phosphates
- i.e. AMP, ADP, ATP
- Base – purines/pyrimidines
- Polynucleotide Structure
- 3’ → 5’ phosphodiester bond between sugar and phosphate
What makes up the secondary structure of DNA and what are the basic characteristics of this?
- Helix is right handed
- Sugar-phosphate backbone
- A-T, C-G form inside of helix
What re the forces that keep the DNA double helix together?
- Weak Forces: hydrogen bonds, hydrophobic, and stacking energy
Define the minor and major groove of DNA.
- Major Groove: occurs where the backbones are far apart
- Minor Groove: occurs where the backbones are close together
- What is the conventional notation of DNA and how is it read?
- What is the RNA transcript and what would it read in relation to the coding strand?
- What is the DNA template strand and what would it read in relation to the coding strand?
- Conventional Notation
- Read 5’ to 3’
- Coding Strand
- Will be the strand similar to RNA transcript (opposite of template)
- ACTGTCGATGCTA
- RNA Transcript
- Homologous to Coding Strand, but U subbed for T
- ACUGUCGAUGCUA
- Template Strand
- TGACAGCTACGAT
- Strand read for RNA replication