Microanatomy Chapter 4

Tissue

an organized aggregation of cells that function in a collective manner

Cells within tissues are connected to each other by…?

-specialized anchoring junctions

Cells can communicate intercellularly via…?

-gap junctions

Another mechanism that permits the cells of a given tissue to function in a unified manner is

-via membrane receptors that generate responses to various stimuli

Four Basic Types of Tissues

-epithelium

-connective tissue

-muscle tissue

-nerve tissue

*Connective Tissue

-underlies or supports the other three basic tissues, both structurally and functionally

*Nerve Tissue

-receives, transmits, and integrates information from outside and inside the body to control activities of the body

Epithelial Cells

-cells are closely apposed, contiguous with one another

• minimal intercellular space

-present at a free surface

-joined by specialized cell-to-cell junctions that create a selective barrier between the external environment and underlying connective tissue

-form glands and gland ducts that help secrete products onto a free surface or into the lumen of a tube

-specialized surface modifications on the free surface

• Ex. simple epithelia → cilia, stratified epithelia → keratinized exterior like the skin

All epithelia rest on the…?

basal lamina

Basal Lamina

-structural attachment site for overlying epithelia cells and underlying connective tissue

Epithelial Cells Connecting to Each Other

-cells either connect by specialized cell-to-cell anchoring junctions or to they connect to underlying connective tissue via specialized cell-to-extracellular matrix anchoring junctions

Embryonic Connective Tissue

-derived from the mesoderm; present in the embryo and within the umbilical fold

-gives rise to many connective tissues in the body

Loose Connective Tissue

-more cellular, less collagen fibers in extracellular matrix

-found more so in close association with epithelia (most epithelia rest on loose connective tissue)

-most of the cells are from the vascular system and are associated with the immune system

• some of the cells that are part of the extracellular matrix are called fibroblasts and actually take part in making/maintaining some of the matrix

Dense Connective Tissue

-more numerous and densely packed collagen fibers

-cells are sparse adn limited to teh fiber-forming cell

Specialized Connective Tissue

-bone, cartilage, blood (plasma = extracellular matrix)

Connective tissue is characterized by…

-extracellular matrix (EM)

• ex. plasma characterizes blood connective tissue

• ex. water bound to hyaluronan aggregates makes up cartilage EM

• ex. minerals of calcium and phosphate molecules associated with collagen fibers makes up bone EM

Muscle Cells characterized by…

-large amounts of contractile proteins actin and myosin in their cytoplasm (these proteins make up the bulk of the cytoplasm and are highly ordered to produce contractile activity)

• actin = forms thin myofilaments

• myosin = forms thick myofilaments

-typically elongated, long axes going in the same direction, nuclei also arranged parallel to muscle cells

Supporting cells of the CNS are called?

-neuroglial cells

-oligodendroglia cells

Supporting cells of the PNS are called?

-Schwann cells

Functions of Nervous System Supporting Cells

-separate neurons from one another

-produce the myelin sheath

-provide phagocytosis to remove cellular debris

-contribute to blood-brain barrier in the CNS

Ganglia

-nerve cell bodies in the PNS (including the autonomic nervous system) that are seen in aggregations and surrounded by satellite cells

Neural Ectoderm

-forms the neural tube and neural crest in the embryo

-forms by invagination of the dorsal ectoderm (epithelial layer) of the embryo

Ependymal Cells

-type of glial cell that lines the ventricles of the brain and the central canal of the spinal cord.

-essential for maintaining the environment within these fluid-filled spaces, particularly by regulating the flow of cerebrospinal fluid

Parenchyma

-the functional tissue of an organ, consisting of the cells and structures responsible for its primary functions

Stroma

-the supporting and structural tissue of an organ 

Most tumors are derived from the cells that…?

-originate from a single germ cell layer

-however, if tumor cells arise from pluripotential stem cells, the tumor may resemble cells originating from all three germ layers

Teratoma

-tumor containing a variety of mature basic tissues that fail to form functional structures