Lecture 2: Cell Biology and Epithelia Flashcards
Basal lamina sublayers
Lamina lucida: laminin + fibronectin (glycoproteins)
Lamina densa: type IV collagen (dense, fine fibers)
Lamina reticularis: only if basement connects to CT; type VII collagen anchoring loops (connect to type III reticular fibers)
Terms for changing epithelium
Metaplasia: change in form/class (adaptive and oncogenic phases)
Hypo/hyperplasia: change in cell number
Hypo/hypertrophy: change in cell size
Dysplasia: increase in abnormal cells, loss of normal function (maladaptive)
Basic forms of junctional proteins
- Gap junctions: connexins (conductive channel via transmembrane proteins)
- Tight junctions (zonula occludens): occludins, claudins (transmembrane proteins)
- Adhering junctions (zonula adherens): cadherins (connect cytoskeletal f-actin via transmembrane proteins)
- Desmosomes (macula adherens): desmogleins (connect w/ cytoskeletal keratin, hemidesmosome -> CT)
Secretion modes
Merocrine: standard hydrophilic molecules
Apocrine: lipids
Holocrine: cell death
Cytocrine: cell to cell
Transcytosis: across the cell
Extracellular Vesicles: products contained in vesicles are released
Types of extracellular vesicles
- Exosomes (multivesicular body)
- Ectosomes (blebbing)
Junctional complex structure
Zonula occludens (band) -> zonula adherentes (band) -> macula adherentes (hemi/desmosomes)
How do blood vessels differ between epithelium and muscle?
The epithelium is not vascularized. Muscles are highly vascularized.
What kind of proteins does the rough ER produce?
Proteins destined for secretion or the cell membrane
What happens to undigestible remains of metabolic processes in cells?
They become residual bodies (exocytosed) or lipofuscin granules (retained, more common in long lived cells)
Cilia structure
9+2 microtubule arrangement composes the axoneme core, which inserts into the basal bodies (9 triplets of microtubules)
Flagellum structure
Same 9+2 and basal bodies of cilia, bound to transmembrane complex that acts as a rotary motor
Primary/monocilium structure
9+0 microtubule arrangement; no central tubules
Microvillus structure
Core of several f-actin filaments inserted into the cytoskeletal actin
Stereocilia
Basically longer, less frequent microvilli. Used as force -> electrical potential signal transducers in the auditory/vestibular systems.
Pseudostratified epithelium
Epithelium with multiple cell shapes where all cells touch the basement membrane but not all are part of the apical junctional complexes.
Symmetric cell division
Cell divides into 2 cells equal to the parent cell
Asymmetric cell division (vertical vs horizontal)
At least 1 child cell is further differentiated compared to the parent. Horizontal division expands the cell sheet, vertical creates another layer (1 cell loses contact with basement membrane)
Ribosomes
Organelles responsible for translation; made of rRNA and ribosomal proteins. Free or attached to rough ER membrane. Basophilic staining
Smooth endoplasmic reticulum
Critical role in lipid and steroid production
Golgi apparatus
Tags vesicles for transport to specific regions of the cell. Creates blank spot inside cell in staining
Mitochondria
Produce energy as ATP; composed of outer membrane and inner cristae. Have their own DNA, RNA, and proteins. Eosinophilic staining
Basal striations
Folds in basal portion of cell with high mt density for basal ion pumps/pore proteins
Vesicles
Membrane enclosed structures that transport proteins/small molecules within or across the cell
Types of intracellular vesicles
- Endosomes
1a. Phagosomes - Lysosomes
- Peroxisomes
Endosomes
Part of endocytosis (pinocytosis/phagocytosis); enclose the uptaken substance from the EC space
Phagosomes
Endosomes created through phagocytosis
Lysosomes
Contain acid hydrolase enzymes to lyse things
Peroxisomes
Help to break down fatty acids via oxidation
Exocytosis
Process of moving substances out to the EC space; can be regulated or constitutive.
Intercellular components of the cytoskeleton
- Thin filaments (f-actin)
- Intermediate filaments (keratins, desmins, etc.)
- Microtubules (tubulin)
Microtubule organizing center (MTOC)
Point of origin for microtubules to radiate out through the cell. Becomes the centrosomes in cell division
Centriole
Organizing point for microtubules
Thin filaments
Composed of actin, sit beneath cell membrane and helps in cell motility and scaffolding
Intermediate filaments
Composed of keratin, desmins, other proteins. Connect with desmosomes/hemidesmosomes for cell adhesion and scaffolding
Microtubules
Composed of tubulin. Primarily act as transport network throughout cell
Junctional complex
Connects epithelial cells, especially in simple epithelia. Limits diffusion across epithelial sheet; fewer junctional proteins makes a leakier tight junction.
Euchromatin
Loosely packed chromatin, allowing access for transcription
Heterochromatin
Tightly packed chromatin, preventing transcription
Nuclear lamins
Fibrous proteins that organize nuclear DNA by binding to the inner nuclear membrane. Helps maintain nucleus shape
Histones
“Spools” that control DNA coiling. Histone modification is a major regulator of transcription. Contain many negative charges and so are basophilic
Nucleolus
rRNA production site in the nucleus. Stains as a strongly basophilic dot.
Types of epithelia
- Simple (squamous, cuboidal, columnar)
- Stratified (squamous non-/keratinized, cuboidal, columnar)
- Pseudostratified
- Transitional (urinary)
Features of extracellular cell membrane
Glycoproteins (glycocalyx), extracellular protein regions/polar lipid heads
Features of transcellular cell membrane space
Fatty acid tails, cholesterol, transmembrane proteins
Features of intracellular cell membrane
Intracellular protein regions, phosphatidylserine (also an immune marker)
Epithelial-to-mesenchymal transition
EMT is the process by which epithelial cells leave the epithelial sheet by removing their junctional proteins to migrate into other spaces
Keratinization
Keratinized epithelium has 1 or more layers of keratin sheets deposited on the apical surface. Acts as waterproof layer.
