General Histology Flashcards
What are the four different tissue types?
Connective tissue
Muscle tissue
Nerve tissue
Epithelial tissue
What are the three subtypes of connective tissue?
Adipose tissue
Cartilage
Bone tissue
What are the five types of neurons and where are the main places they are found?
Bipolar neurons- Retina Unipolar/Pseudopolar neurons- Spine and ganglia Multipolar neurons- Motor cells Pyramidal cells- Hippocampus Purkinje cells- Cerebellum
What are the 5 types of nervous tissue?
Neurons Neuroglia Melanocytes Odontoblasts Chromaffin
What is the role of glial cells and what are the subtypes?
Glial cells serve a homeostatic role (structural and nutritional support, insulation of neurons, phagocytosis of pathogens)
Subtypes include Astrocytes Oligodendrocytes Schwann cells Microglia Ependymal cells
What are astrocytes?
Astrocytes are star-shaped glial cells of the central nervous system that support the epithelial cells of the blood-brain barrier, maintain extracellular osmotic homeostasis, and moderate the healing and scarring process.
What are oligodendrocytes?
Oligodendrocytes are glial cells of the central nervous system that myelinates nerves.
What are schwann cells?
Schwann cells are glial cell that myelinates the axons of motor and sensory peripheral neurons. Disorders of these cells include neoplasms (e.g., schwannoma, acoustic neuroma) and demyelinating disorders (e.g., Charcot–Marie–Tooth disease, Guillain–Barré syndrome).
What are microglia?
Microglia are e macrophages of the central nervous system, which activate in response to tissue damage. Derived from mesoderm.
What are ependymal cells?
Ependymal cells are a specialized type of epithelial cells that line the ventricular system of the brain and play a key role in the production of cerebrospinal fluid.
What are melanocytes and where are they found?
Melanocytes are the pigment-containing cells of the skin that produce melanin. Melanin production is stimulated by melanocyte stimulating hormone and ultraviolet radiation. Malignant transformation of melanocytes causes melanoma. Also found in retina.
What are odontoblasts and where are they found?
Odontoblasts are cells involved in the formation of dentin in teeth. Originate from neural crest cells.
What are chromaffin cells and where are they found?
Chromaffin cells are a group of neuroendocrine cells found in the adrenal medulla and other ganglia of the sympathetic nervous system. Release epinephrine and norepinephrine.
What are the types of muscle tissue?
Striated (includes cardiac and skeletal)
Smooth muscle
What are the two functional types of epithelium?
Surface and glandular epithelium
Epithelial tissue covers all inner and outer surfaces of the body EXCEPT what?
The synovial membrane is composed of synoviocytes (not epithelial cells!), which line the inner surfaces of joint capsules, synovial bursa, and tendon sheaths.
What types of epithelia are formed from the three germ layers?
Ectoderm- Epithelium of skin and skin appendages.
Mesoderm- Epithelium of serous membranes (mesothelium) which is found in peritoneum, pleural, and pericardial cavities. ALSO Cells lining the inner surface of blood and lymphatic vessels (endothelium).
Endoderm: epithelium of the respiratory and gastrointestinal tract.
What are the differences between simple, pseudostratified, and stratified epithelium?
Simple epithelium: a single layer of epithelial cells with all cells attached to the basement membrane
Pseudostratified epithelium: a single layer of cells with the appearance of multiple layers as a result of the nuclei positioned at different levels
Stratified epithelium: two or more cell layers with the basal layer attached to the basement membrane
What are differences between squamous, cuboidal, and columnar epithelium?
Flat (squamous epithelium)
Appearance: Upper cells have a squamous (flat) shape (width > height).
Examples: skin , esophagus , cervix , serous membrane (e.g., peritoneum)
Cube-shaped (cuboidal epithelium)
Appearance: Upper cells have a cube-like shape (width = height).
Examples: bile ducts , renal tubules
Column-shaped (columnar epithelium)
Appearance: Upper cells have a rectangular or cylindrical shape (width < height).
Examples: intestine , respiratory tract (respiratory epithelium)
Microvilli and stereocilia are composed of (?) while kinocilia are composed of (?)
Microvilli and stereocilia are composed of ACTIN FILAMENTS while kinocilia are composed of MICROTUBULES
What are the two intraepithelial gland types?
- Goblet cells
Definition: single intraepithelial glandular cells with a vacuole that is characteristically filled with mucus (goblet form)
Function: secrete mucus (mucins)
Distribution
Small and large intestines
Nasal mucosa and respiratory tract - Secretory epithelium
Definition: conglomerates of columnar epithelial cells with a bright cytoplasm (filled with mucus) and no vacuole
Distribution: e.g., the surface epithelium of the stomach and cervical canal is entirely composed of secretory epithelium
What are the two components of a typical extrathelial gland?
- Terminal ends
Definition: A closed glandular section that is connected to the excretory ducts and is the site of secretion production. There are numerous types of terminal ends.
Function: production and release of secretions into the lumen (the secretion drains from here into the excretory duct system) - Definition: ducts lined with epithelial cells that connect glandular cells (in the acinus) with the opening of the gland
Function: drainage of secretion; changes in the nature of the secretion (e.g., through the addition/removal of ions)
Shapes: Because extraepithelial glands are usually subdivided into lobules (or lobuli) by connective tissue septa, there are various forms of excretory ducts.
What are the four shapes of exocrine gland terminal ends?
- Acinar glands
Form: berry-like , narrow lumen
Examples: parotid gland, pancreas - Alveolar glands
Shape: sac-like , wide lumen
Examples: apocrine sweat glands - Tubular glands
Shape: tubular; wide, elongated lumen
Examples: gastric glands (foveolas in the stomach), colonic crypts
Subtypes
Simple branched tubular (e.g., meibomian glands)
Coiled tubular (e.g., eccrine sweat glands) - Mixed forms: tubuloacinar, tubuloalveolar
What are the 4 secretory mechanisms of exocrine glands?
- Eccrine secretion
Definition: release of ions and small molecules through transmembrane proteins
Mechanism: membrane protein transport
Distribution: in almost all exocrine gland cells - Merocrine secretion
Definition: release of secretions rich in proteins through fusion of cytosolic vesicles with the cell membrane
Mechanism: exocytosis
Distribution: in almost all exocrine glandular cells - Apocrine secretion
Definition: release of secretions rich in lipids via budding off of a part of the apical cytoplasm
Mechanism: A portion of the cell membrane buds off with cytoplasm containing the secretory product (e.g., milk lipid droplets). As a result, the gland cell becomes smaller.
Distribution: found only in apocrine sweat glands and lactating mammary glands - Holocrine secretion
Definition: release of the entire cytoplasmic content through destruction of the gland cell
Mechanism: apoptosis of the glandular cell
Distribution: found only in sebaceous glands
