The document summarizes the structure and functions of human cells and their connections to other cells. It describes three main types of cell junctions: tight junctions, desmosomes, and gap junctions. Tight junctions form a barrier between cells to prevent molecules from passing between them. Desmosomes firmly hold adjacent cells together, especially in tissues that experience stretching. Gap junctions allow small molecules and electrical signals to pass directly between cells through channel proteins. Overall, cell junctions are important for tissue structure, cell communication, and various physiological processes.

1. Structure of human cell &
functions

12. • 5. Provides a framework for the arrangement of an
ordered sequence of protein molecules e.g.
enzymes,pumps,receptors,ions,channels, in a
functionally meaningful pattern.
• 6.Links adjacent cells together by junctional
complexes to form tissues.

32. Tight junction
• In this membranes of two cells become opposed & outer
layers of membranes fuse strongly,thus obliterating the space
between the cells.
• Seen along the apical margins of cells in epithelium like
intestinal mucosa,walls of renal tubules.
• Forms barrier to the movement of ions and other solutes from
one side of epithelium to other.

33. Desmosomes or Adherens junction
• Here two membranes are separated by 15-20nm space.
• There is dense accumulation of proteins on both
surfaces of membrane with fibers extending from
cytoplasmic surface of each membrane into the cell.
• Transmembrane glycoproteins called cadherins joins
the cells.
• This holds adjacent cells firmly together in areas that
are subjected to stretching like skin.
• Also resist separation during various contractile
activities such as when food moves through the GIT.

34. Gap junctions or Nexus
• There is 2-20nm space between the opposing membranes.
• This gap is filled with densly packed particles through each
of which there appears to be a channel(tiny fluid filled
tunnels) that connects the two cells.
• The diameter of each channel is regulated by ca++,PH,and
voltage.
• Permits rapid propagation of electrical potential changes
from one cell to another e.g cardiac & smooth muscle cells.
• Also permits the direct transfer of ions and other small
molecules up to MW1000 e.g sugars,amino acids between
the cells without traversing the extracellular space.

38. Functions of CAM”S
• Role in embryonic development.
• Formation of nervous system.
• Holding tissues together.
• Inflammation & wound healing.
• Metastasis of tumours.
• Cells with abnormal CAMs have a higher rate
of apoptosis.

41. • Abnormal apoptosis occurs in autoimmune
diseases,degenerative diseases and cancers.

42. THANK YOU