A&P Lab Tissue

endobiosis

• fertilization…sperm to ova

• diploid = zygote

Differentiation

• the process by which cells take on different shape and function

Blastula

• result of zygote mitotic divisions

• tight ball of non-differentiated cells

Gastrula

• as divisions continue in the blastula…

• hollow ball stage

• three layers of cell wall form → differentiation

Tri -lamiar embryo

• formed when the gastrula differentiates and forms three layers

Three Enbryonic Germ Layers 

• endoderm

• mesoderm

• ectoderm

4 primary tissure ttpes

Stem Cells

• Cells which can differentiate into other cell types are called 

• the less differentiated, the greater the potential for diversity in differentiation

what are blastula cells classified as and why?

• Pleuripotent

• they can differentiate into any tissue/Cell type

what are the only true stem cells we are born with?

• Mesenchyme and bone marrow are the only true stem cells we are born with

Epithelial tissue

• covers all body surfaces, lines internal organs and cavities, and forms glandular tissue. Because it directly faces the external environment or specialized internal spaces, it serves as the body's primary protective boundary

functions of epithelial tissue

• Protection: Shields underlying tissues from physical abrasion, pathogens, and chemical damage.

• Absorption: Takes up nutrients and fluids (e.g., in the digestive tract).

• Secretion: Releases substances such as mucus, enzymes, or hormones.

• Filtration & Excretion: Controls the movement of waste and filtered substances across cellular barriers (e.g., in the kidneys)

Is epithelium mitotically active?

• YES

• High rate of cell division to continuously regenerate and repair damaged surface layers

is epithelium vascular?

• NO

• Lacks its own blood vessels; nutrients and oxygen diffuse into the cells from underlying connective tissue

is epithelium highly cellular?

• YES

• Composed almost entirely of densely packed cells with very little extracellular matrix in between.

is epithelium polar?

• YES

• 2 different structural ends: apical surface + basal lamina

Apical Surface of epithelial cells

• The top surface facing the exterior environment or body lumen

• features specialized structures such as cilia (movement of fluids), microvilli (increasing surface area for absorption), keratin (waterproofing/protection), or pores.

basal lamina

• a thin, gel-like layer of extracellular matrix that sits directly beneath epithelial and endothelial cells, anchoring them to the underlying connective tissue

junction complexes that hold epithelial cells?

• tight junctions

• desosomes

• gap junctions

• adherens junctions + hemidesmosomes

  

Tight Junctions

• Interlocking membrane proteins that form continuous, fluid-tight seals to prevent molecules from leaking between cells

Desmosomes

• Anchoring junctions linked to intracellular intermediate filaments that act like spot welds, providing strength against mechanical stress and stretching

Adherens junctions + Hemidesmosomes

• Provide additional physical anchoring between neighboring cells and attach the basal surface to the underlying extracellular matrix

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How are epithelium layers arranged?

• Simple: Single layer of cells; optimized for absorption, secretion, and filtration.

• Stratified: Two or more layers of cells; designed for high-friction areas needing protection.

cell shapes of epithelium