1
Q
Types of Tissue
A
- Epithelial
- Connective
- Muscular
- Nervous
2
Q
Origin of Tissues
A
- Primary germ layers in embryo: endoderm, mesoderm, ectoderm
- Epithelium comes from all 3 layers
- endoderm: forms epithelial lining of GI & respiratory
- mesoderm: forms epithelium lining of body cavities
- ectoderm: forms epidermis of skin
- connective tissue & muscular from mesoderm
- nerve tissue from ectoderm
3
Q
Cell Junctions
A
- tight junctions
- adherens junctions
- gap junctions
- desmosomes
- hemidesmosomes
4
Q
Tight Junctions
A
- strands of transmembrane proteins that fuse the outer surface of plasma membrane
- seal off intercellular spaces and inhibit passage of substances between cells (eg. Epithelial cells that line intestine or urinary bladder
5
Q
Adherens Junctions
A
- transmembrane proteins are connected to microfilaments on the inside of the membrane and to similar proteins of adjacent cell across in the intercellular space
- resist separation
6
Q
Gap Junctions
A
- membrane proteins form channels
- substances can diffuse from one cell to another
7
Q
Desmosomes
A
- like adherens junctions but contain intermediate filaments that extend across opposite side
- resist separation (eg. Epidermal cells)
8
Q
Hemidesmosomes
A
-resemble desmosomes but link the cell to a basement membrane
9
Q
Features of Epithelial Tissue
A
- tightly packed cells forming continuous sheets
- little or no extra cellular material between cells
- cells sit on basement membrane
- avascular:nutrients diffuse in from underlying connective tissue
- good nerve supply
- rapid cell division
10
Q
Basement Membrane
A
- Extracellular layer that consists of:
- Basal lamina
- Reticular lamina
- Functions:
- anchor epithelial cells to connective tissue
- form a surface along which cells migrate during growth
- restrict passage of large molecules
11
Q
Basal Lamina of Basement Membrane
A
- closer to basal surface of epithelial cells
- secreted by epithelial cells
- contains collagen and other fibres
12
Q
Reticular Lamina of Basement Membrane
A
- closer to underlying connective tissue
- secreted by connective tissue cells (fibroblasts)
- contains reticular fibres
13
Q
Classification of Epithelium
A
- By arrangement of cells into layers:
- simple
- stratified
- pseudo-stratified
- By shape of surface cell:
- squamous
- cuboidal
- columnar
- transitional
14
Q
Simple Squamous
A
- single layer of flat cells
- flattened oval nucleus
- found in blood vessels (endothelium) and body cavities (mesothelium)
- functions: is very thin so controls:
- filtration
- diffusion
- secretion
15
Q
Simple Cuboidal
A
- single layer of cuboidal cells
- round centrally located nucleus
- found in lining of kidney tubules, secretory portion of glands
- functions: absorption and secretion
16
Q
Nonciliated Simple Columnar
A
- single layer of rectangular cells
- oval nucleus near base of cell
- may have microvilli
- at be modified to goblet cells (unicellular glands) that secrete mucous
- located in lining of GI from stomach to rectum, large ducts of glands
- function: absorption and secretion of mucous
17
Q
Ciliates Simple Columnar Epithelium
A
- single layer of ciliates rectangular cells
- oval nucleus near base of cells
- may have goblet cells
- located in lining of uterine tubes, bronchioles
- functions:
- move oocytes expelled from ovaries through uterine tube to uterus
- move mucous and trapped foreign particles in respiratory tract toward throat
18
Q
Pseudostratified Columnar
A
- single layer of cells
- not all cells reach apical surface
- all cells rest on basement membrane
- nuclei are found at different levels so it looks multilayered
- may or may not have cilia and goblet cells
- located in lining of most upper respiratory tract and epididymis, larger ducts of glands
- functions:
- absorption
- secretion of mucous that traps foreign particles and sweep away
19
Q
Stratified Squamous Epithelium
A
- several layers thick
- apical layer is formed of Squamous cells
- deeper layers vary from cuboidal to columnar
- basal cells divide and push upward toward apical layer where they die
- two types:
- keratinized: surface cells are dead and filled with keratin
- non-keratinzed: surface cells are dead but no keratin
- located in epidermis of skin (keratinized) or lines wet surfaces (non-keratinized)
- function: protect against abrasion, water loss, UV and foreign invasion
20
Q
Rare types of stratified epithelium
A
- stratified cuboidal and stratified columnar
- found in ducts of some glands in urethra
- mainly protective
21
Q
Transitional Epithelium
A
- multilayered and looks like stratified cuboidal
- surface cells varying in shape from large rounded to flat if stretched
- located in lining of hollow organs that expand from within (bladder/ureter)
- allows urinary organs to stretch and hold variable amount of fluid
22
Q
Glandular Epithelium
A
- Exocrine Glands
- Endocrine Glands
- Mixed Glands
23
Q
Structural Classification of Exocrine Glands
A
- secrete onto free surface of epithelial layer or into ducts
- eg: sweat/salivary
- classified into:
- unicellular glands
- multicellular glands
- most of exocrine glands
- classified according to shape of duct:
- simple: unbranched
- compound: branched
- Shape of secretory portion:
- tubular
- Acinar (alveolar) when rounded
- tubuloacinar: both
24
Q
Functional Classification of Exocrine Glands
A
- Merocrine (eccrine):
- cells release products by exocytosis
- most glands: saliva, digestive enzymes and sweat
- Apocrine
- accumulate the secretory product of the upper surface of cell which pinches off. Remaining part of cell only repairs itself.
- only in mammary gland
- Holocrine
- accumulate the secretory product in the cystol; whole cells rupture to release products. Cells are then replaced
- sebaceous glands
25
Connective Tissue
- most abundant and most widely distributed
- binds together
- supports and strengthens other tissue
- protects and insulates internal organs
- blood transports nutrients and wastes
- source of immune response
- fat tissue stores energy
26
Characteristics of Connective Tissue
- cells rarely touch due to extracellular matrix
- matrix: fibres and ground substance secreted by cells
- does not occur on free surface
- good blood supply except cartilage and tendons
- good nerves supply except cartilage
27
Cell Types of Connective Tissue
- blast cells: retain ability to divide and produce matrix
- fibroblasts, chondroblasts, osteoblasts
- cyte cells: mature cell that have reduced capacity to divide or produce matrix
- fibrocytes, chondrocytes, osteocytes
- macrophages: develop from monocytes. Engulf bacteria and debris by phagocytosis
- Plasma cells: develop from B lymphocytes and produce antibodies
- mast cells: produce histamine to dilate small blood vessels
- adipocytes: store fat
- white blood cells: migrate to sites of infection (neutrophils)
28
Connective Tissue Extracellular Matrix Ground Substances
- support the cells and fibres
- helps determine the consistency of the matrix
- contains many large molecules (adhesion proteins and carbohydrates)
- binds collagen fibres to ground substance
29
Connective Tissue Extracellular Matrix Fibres
- collagen (most abundant)
- formed from collagen
- tough, resistant to pull, yet pliable
- Elastin
- lungs, blood vessels, ear cartilage
- smaller diameter fibres formed from elastin
- can stretch and return to shape
- Reticular
- spleen, lymph nodes
- formed from collagen
- thin branched fibres that form framework of organs
30
Classification of Connective Tissue
- Embryonic
- mesenchyme
- mucous
- mature
- connective tissue proper
- loose connective tissue
- areolar
- adipose
- reticular
- dense connective tissue
- dense regular
- dense irregular
- elastic
- supporting connective (cartilage and bone)
- liquid (blood, lymph)
