Histology #1- Tissues
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Histology #1- Tissues
Flashcards for week 1 of UCVM Histology
Define histology and cytology
: microscopic anatomy (microanatomy uses a LM and fine structure uses EM) - so the study of microscopic tissue anatomy
: the study of cells typically from body fluids (smears)
*What are the five cellular characteristics of epithelia?
I) the cohesive interaction between cells allowing the formation of continuous cell layers
II) the existence of three types of membrane domains
: apical, lateral, basal
III) the existence of tight junctions between apical and lateral domains
IV) the polarized distribution of the different organelles and components of the cytoskeleton
V) the quasi-immobility of the group of epithelial cells relative to the local environment
What are the specialized structural/adhesions connecting cells in the epithelium?
adherens junctions (junction that allows the connection between cells to form lawn)
What are the Four different types of tissue?
1. Connective tissue
: Few cells, lots of extra cellular matrix (ECM)- lots of space! * specialised to bind
2. Nervous tissue
: Excitable cells - membrane potential (have ion channels) *specialised to excite/conduct
3. Muscle tissue
: contractile cells- intracellular motors (cytoskeleton)-->contains motor proteins in the cell that contract *specialized to contract
: Lawn of cells -intercellular adhesion (tight epithelium barrier, little ECM) *specialized to form lawns
What does Epithelium sit on?
A basement membrane (which is ECM)
What are the terms used to describe the in and out sides of the epithelium?
in = basal (so the attached side where basement membrane is)
out = apical (free not attached side)
Is the epithelia avascular?
YES -but the connective tissue is quite vascularized and inervates the epithelia
What do we mean when we say the epithelia have a high turnover?
Lots of cell division
and there is a large stem cell population that feeds the turnover
What are the structural features of epithelia?
"lawn of cells"
has a basement membrane
polarity (by apical and basal cell surfaces)
avascular (but richly inervated)
What are the fibrous ropes and tubes and connectors that give the epithelium structural integrity?
microfilaments (found in the top villi)
microtubules (form cytoskeleton)
intermediate filaments ( bind the attachment sites)
What are the functional roles of Epithelia?
1. physical protection
2. control fluid flow -permeability/ capacitance
3. actively moves fluid across surfaces
4. produces specialized secretions (ie the glandular epithelium)
5. provides sensation (neuroepithelia)
What are the different types of epithelia?
: squamous, cuboidal, columnar
: squamous, columnar
and pseudostratified columnar
How do glands develop?
Glands develop as invaginations of epithelium
What are various types of glands defined by?
architecture: tubular, acinar, tubuloacinar
In the gland what are the duct and the glandular parts roles?
Duct- conduit for exocrine glands (so ducts go to surface so secretions can occur)
Glandular part- secretory
Do all glands have ducts?
NO- ENDOCRINE glands do not have ducts
during embryonic development these glands detach from their epithelial origins and have no ducts- their secretions go into the blood stream (ie pituitary)
What are the modes of secretion for exocrine glands?
Merocrine gland (is salivary gland) the material is manufactured in the cells and secreted into the duct
Apocrine gland (i.e. sweat gland) -part of the cells pinch off and contribute to the secretion
Holocrine gland (sebaceous gland)- disintegrating cells and its content dissociate and become the secretion
What is an example of an organ that has both exocrine and endocrine secretions?