Tissue Types in Histology: Epithelial Tissue, Connective Tissue, Muscle Tissue, Nervous Tissue

Histology is the study of the microscopic structure of tissues, which are integral in forming the various organs of the body. Four primary types of tissue are fundamental to understanding human anatomy and physiology, each with distinct structures and functions.


Epithelial Tissue


Epithelial tissue forms the protective outer layer of the body and lines the surfaces of organs and cavities. This tissue is involved in functions such as secretion, absorption, and filtration. The cells are tightly packed, with minimal extracellular matrix, and are arranged in sheets. Epithelial tissue is also classified by the shape of cells and number of layers, including simple (one layer), stratified (multiple layers), squamous (flat), cuboidal (cube-shaped), and columnar (tall).


Connective Tissue


Connective tissue supports, binds, and separates other tissues and organs. With a variety of functions, it is characterized by an abundance of extracellular matrix, which is a network of proteins like collagen, and often includes reticular fibers. Types of connective tissue include vascular tissue such as blood, which transports oxygen and nutrients, and lymph, a key component of the immune system. Other types, such as bone and cartilage, provide structural support.


Muscle Tissue


Muscle tissue is responsible for producing movement, both voluntary and involuntary. There are three types of muscle tissue: skeletal muscle, which is attached to bones; cardiac muscle, found only in the heart; and smooth muscle, located in walls of internal organs. Muscle fibers contain contractile proteins that enable the contraction and relaxation of muscles, essential for movement and bodily functions.


Nervous Tissue


Nervous tissue is the main component of the nervous system, consisting of the brain, spinal cord, and peripheral nerves. It contains neurons, which are specialized to transmit electrical signals, and supporting glial cells. This tissue is crucial for controlling and communicating information throughout the body, thus playing a pivotal role in regulating bodily functions and responding to stimuli.

October 18, 2025
𝗦𝗶𝗺𝗽𝗹𝗲 𝗦𝘂𝗺𝗺𝗮𝗿𝘆: This study explores how we can improve lab-grown liver cells for medical research and drug testing. The MTMLab team works with induced pluripotent stem cells (iPSCs) - special cells that can be transformed into liver-like cells - because real human liver cells are hard to obtain. However, these lab-grown liver cells don't function as well as mature adult liver cells. The research team discovered that the surface environment where these cells grow is crucial for their development. We created tiny fiber scaffolds made from different materials like collagen, decellularized livers, and chitosan that mimic the natural structure around liver cells. When liver cells were grown on these specially designed nanofibers for three weeks, they displayed higher function compared to cells grown on standard surfaces. Our key finding was that both the material composition and the nanoscale fiber structure were important - stiffer synthetic fibers or softer materials without the appropriate topography or composition prevented proper cell maturation. This research helps create better lab models of human liver tissue that can be used for testing new drugs and studying liver diseases more effectively.

2025 BMES Annual Meeting - MTMLab Member Presentations!

October 7, 2025
Owen Lally Modeling the synergistic effects of alcohol and fats on liver disease via engineered cocultures In Vitro Liver Toxicology Testing of Rat and Dog Hepatocytes to Reduce In Vivo Regulatory Requirements Nathan Shelton Enhancing the Functions and Hepatitis B Virus Infectability of Primary Human Hepatocytes Protein Microarrays to Probe Synergistic Effects of Extracellular Matrix Composition and Stiffness on Liver Macrophages Lesly Villarreal Engineering a 3D Placental Trophoblast Invasion Platform Via Droplet Microfluidics Gas-permeable Plates to Model Synergetic Effects of Oxygen and Endothelial Factors on Liver Zonation Emanuele Spanghero Modeling the Interplay Between Liver and Heart Diseases via a Human Dual-Organ Platform Engineering High Cell Density Beating Cords of Cardiomyocytes and Fibroblasts via Photopatterned Alginate

MTMLab Research Summary: Improving Lab-Grown Liver Cell Maturation

May 7, 2025
Our latest study addresses a critical challenge in liver tissue engineering: stem cell-derived liver cells (iHeps) typically remain functionally immature, limiting their usefulness for drug testing and disease modeling. Our research team created 3D microtissues using droplet microfluidics technology by: • Encapsulating iHeps in tiny collagen gel droplets (~250 μm diameter) • Coating these structures with various non-parenchymal cells (NPCs) • Testing different combinations and sequences of supporting cells Key findings: 1) Embryonic fibroblasts and liver sinusoidal endothelial cells (LSECs) produced the most mature iHeps compared to other tested cell types 2) Sequential application of cell signals (embryonic fibroblasts first, then LSECs) yielded optimal maturation 3) Specific growth factors like stromal-derived factor-1 alpha were identified as important maturation enhancers 4) Gene expression analysis confirmed that LSEC/iHep microtissues closely resembled adult human liver cells This platform enables researchers to identify critical cellular interactions and molecular signals that drive liver cell maturation, providing valuable insights for developing more physiologically relevant liver models for drug screening and regenerative medicine applications. https://www.sciencedirect.com/science/article/pii/S174270612500193X SIMPLE SUMMARY: Embryonic fibroblasts and liver sinusoidal endothelial cells dramatically improved iHep maturation compared to other cell types tested, producing more functionally mature liver cells. Sequential application proved crucial—adding embryonic fibroblasts first, followed by endothelial cells, yielded optimal maturation. Specific growth factors including stromal-derived factor-1 enhanced this process. This research enables creation of more authentic mini-liver tissues that function like human liver. These improved models support better drug testing, disease research, and regenerative medicine applications.