Lecture 5: Life of a Cell Flashcards
Embryonic stem cell
ESC = true human stem cell, not found in adults
Stem cell
Cell that can divide indefinitely, self-regenerate, and differentiate into specific cell types
Progenitor cell
Cell that retains self-regeneration and some pluripotency; technically more differentiated than a true stem cell
Precursor cell
Differentiating cell that is not able to self-regenerate
Adult “stem” cells
Most pluripotent cell within a tissue.
-MSC: CT, muscle, adipose
-HSC: blood cells, some CT
-No stem cells for cardiac muscle
-Neural SCs
Spermato/oogonium: male/female germ line SCs
-Myosatellite cells
Cell cycle phases
- Gap-1 (G1)
- S-phase (DNA replication)
- Gap-2 (G2)
- Prophase
- Metaphase
- Anaphase
- Telophase
Quiescent cells
Cells that have left the cell cycle (gap-0/G0 phase); aka terminally differentiated cells
Chromosome
DNA strand; 2 homologous chromatids joined by a centromere
Mitosis chromosome counting
2n1x (1 cell) -> 2n2x (1 cell) -> 2n1x (2 cells)
Meiosis chromosome counting
2n1x (1 cell) -> 2n2x (1 cell) -> 1n2x (2 cells) -> 1n1x (4 cells)
n, x system for chromatid counting counting
n = number of distinct chromatids (n = 23 in humans)
x = number of exact copies of each chromatid (x = 1 normally, x = 2 after DNA replication)
Gamete development stages
- Stem/progenitor cells (spermato-/oogonia)
- Pre-meiosis I (primary spermato-/oocytes)
- Pre-meiosis II (secondary spermato-/oocytes)
- (Male) precursors (spermatids)
- Adult cells: (spermatozoa, ova)
Telomeres
Repetitive DNA sequences at chromosome ends that protect them from fraying. Telomeres shorten after each division.
Types of cell death
- Apoptosis
- Necrosis/necroptosis
- Autophagy
- Senescence
- NETosis
- Many others (ferroptosis, pyroptosis, etc.)
Apoptosis
Caspase-dependent cell suicide; orderly, non-immunogenic destruction
Necrosis/necroptosis
Non-caspase dependent cell death pathway; results in extracellularization of DNA/RNA (immunogenic DAMPs)
DAMPs/PAMPs
Damage/pathogen associated molecular patterns. Recognized by pattern recognition receptors (PRRs) to stimulate immune activity
Autophagy
Compartmentalization and destruction of cytoplasm/organelles. Can rescue a stressed cell or lead to traditional cell death.
Senescence
Exiting of cell cycle, leaves cell incapable of replication and creates secretome complex. Immortal cells escape senescence. Often caused by irreparable DNA damage; anti-tumor function.
Secretome
Substances secreted by a senescent cell telling the immune system to kill and clean. Can induce inflammation and fibrosis.
Types of tissue necrosis
- Coagulative
- Liquefactive
- Caseous
- Fat
- Fibrinoid
- Gangrenous
Tissue necrosis by rate of chemical dissolution
Fast = liquefactive
Normal = caseous
Slow = coagulative
Coagulative necrosis
Firm area due to acute blood loss to region. Cells are preserved due to limited macrophage activity
Liquefactive necrosis
Fluid products, primarily caused by neutrophil response
Caseous necrosis
“Cheese-like”; balanced macrophage, neutrophil, lymphocyte response; disease specific process e.g. TB
Fat necrosis
Lipid dominated necrotic tissue; adipose necrosis
Fibrinoid necrosis
Caused by immune response in blood; creates deposits similar to clots
Gangrenous necrosis
Occurs when affected tissue is too large to be resolved by immune response or scarring, or if area is inaccessible to the immune system.
Pus
Whitish fluid primarily made of cell debris from dying immune cells. Mechanically forces foreign material out of the tissue
Differential stages of spermatogonia
Stem cells: Type A dense
Mitotically active: Type A pale
Final mitotic division: Type B pale
