General History of Histology Flashcards
Definition of Tissue
Groups of cells with a common function
Major tissue types
Epithelial, connective, muscle, nervous
Tissues are classified by…
-Embryological origin
-Composition of extracellular matrix (ECM)
-Structure
-Function
Embryological Origin of Tissues
-Primary Germ layers
-Formed during gastrulation of blastocyst (aka histogenesis)
Primary germ layers
Endoderm (inner), mesoderm (middle), ectoderm (outer)
How are blastocysts formed?
Zygotes (baby eggs) continuously split in half till they form a ball
What’s gastrulation?
Happens when cells migrate inward to make an upside-down U shape & change to form the primary germ layers.
Ectoderm (outer layer)
-Epidermis cells
-Brain neuron
-Peripheral nervous system neuron
Mesoderm (middle layer)
-Notochord cells
-Skeletal muscle cells
-Kidney tubule cells
-Red blood cells
Endoderm (inner layer)
-Pancreatic acinar cells
-Thyroid follicular cells
-Lung alveolar cells
Definition of Extracellular Matrix (ECM)
Complex, nonliving material found btwn cells
The amount of _____ varies. Epithelium has very little _____ & lots of cells; some connective tissues are primarily composed of _____ with very few cells.
…ECM…
What is ECM made of?
Water, proteins, glycoproteins, and proteoglycans
ECM function?
To connect cells and/or aid in communication
_____ is usually made by cells, so it’s considered organic material
ECM
Cell connections
Integrins, Desmosomes, Tight junction, and gap junction
Definition of integrins
Proteins that attach to extracellular material
Not all cell/tissue types of large amts of _____, so they’re all attached to each other.
…matrix…
3 major forms of cellular connections
Desmosomes, tight junction, and gap junction
Definition of desmosomes
Direct connections btwn cells/kinda loose like simple stitching (ex: epidermal cells)
Definition of tight junctions
Cells joined by fused membrane proteins/REALLY secure to prevent leakage (ex: lining of intestines)
Definition of gap junctions
Membrane channels attach to one another; can allow transport & fuse membranes (ex: heart muscle cells)
