Histology of Tissues in Vertebrate Organs

Histology flashcards to review key concepts about tissues in vertebrate organs.

Four principal groups of animal tissue

Epithelial, connective, muscle, and nerve.

Epithelial Tissue

Sheets of tightly packed cells that protect from fluid loss, infection, and injury; lines organs and cavities.

Types of Epithelial Tissue

Simple epithelium (single layer) and stratified epithelium (multiple tiers).

Shapes of Epithelial Cells

Squamous (flat discs), cuboidal (square blocks), and columnar (masonry bricks).

Glandular Epithelia

Line organs and absorb/secrete chemical solutions (e.g., in the digestive tract).

Connective Tissue

Supports body parts and holds them together; cells are spaced within an extracellular matrix of fibers.

Loose Connective Tissue

Most widespread type; binds epithelial tissue to underlying structures and holds organs in place.

Adipose Tissue

Similar to loose connective tissue but also stores fat molecules.

Fibrous Connective Tissue

Contains densely packed collagen fibers arranged in parallel bundles, maximizing strength (e.g., tendons and ligaments).

Cartilage

Contains chondroitin sulfate and collagen fibers; strong and flexible, serving as the endoskeleton of some vertebrates.

Osteoblasts

Bone-forming cells involved in calcifying cartilage.

Hydroxyapatite

Substance formed when calcium, magnesium, and phosphate ions interact with the collagen matrix in bone.

Muscle Tissue

Composed of long cells called muscle fibers, made up of myofibrils containing actin and myosin for contraction.

Types of Muscle Tissue

Smooth, skeletal, and cardiac.

Nerve Tissue

Transfers information from one part of the body to another via neurons.

Neurons

Nerve cells with extensions called dendrites and axons that transmit nerve impulses.

Spinal Cord and Brain

Comprise the central nervous system (CNS) of vertebrates, containing most nerve cell bodies.

Glia

Supporting cells in the nervous system, filling spaces between neurons.

Artery vs. Vein

Arteries have thicker walls (elastic and smooth muscle) and maintain a circular shape, while veins have thinner walls and collapse into irregular shapes.

Nerve Fascicles

Bundles of nerve fibers surrounded by connective tissue within a nerve.

Schwann Cells

Glial cells that envelop and insulate axons of nerve fibers, speeding up electrical impulses.

Adipocytes

Hollow cells in adipose tissue that contain lipid droplets, displacing cytoplasm and nucleus to the edge.

Chondrocytes

Cells embedded in the glycoprotein matrix (ground substance) of hyaline cartilage.

Lacunae

Hollows in the matrix of cartilage where chondrocytes sit.

Haversian Canals

Central canals in compact bone containing blood and lymphatic vessels.

Osteocytes

Cells trapped within the mineralized extracellular matrix of bone.

Canaliculi

Branches connecting lacunae with the Haversian system, providing osteocytes access to blood and lymph.

Islets of Langerhans

Groups of cells in the pancreas containing endocrine secretory alpha and beta cells.

Beta Cells

Secrete insulin in the pancreas.

Alpha Cells

Secrete glucagon in the pancreas.

Nephron

Functional unit of the kidney that filters blood, returning useful molecules and ions and removing waste.

Glomeruli

Capillaries in the kidney that filter blood, preventing passage of red/white blood cells or proteins into the filtrate.

Loop of Henle

Found within the medulla of the kidney.

Collecting Tubules

Lead ultimately to the ureter in the kidney.

Villi

Extensive infolding of the inner intestinal wall, filled with capillaries and lymphatic vessels.

Microvilli

Small projections on the apical surface of absorptive cells in the intestine, increasing surface area.

Goblet Cells

Mucus-containing cells in the intestinal epithelium.

Seminiferous Tubules

Long, twisting tubules in the testis where sperm production occurs.

Spermatogonia

Germ cells occupying the periphery of the seminiferous tubules, closely associated with Sertoli cells.

Sertoli Cells

Nutritive cells associated with spermatogonia in the testis.

Spermatogenesis

The process of sperm formation, controlled by Follicle stimulating hormone (FSH).

Leydig Cells

Secrete testosterone under the influence of leutinizing hormone (LH).

Oocytes

Developing egg cells found in follicles in the ovary.

Zona Pellucida

Clear, glycoprotein layer surrounding the oocyte.

Granulosa Cells

Several layers of cells surrounding the primary oocyte within a follicle.

Corona Radiata

Group of cells surrounding the expelled oocyte.

Hepatic Lobules

Polygonal divisions of the liver.

Sinusoids

Endothelial-lined spaces in the liver similar to capillaries, allowing direct contact of blood with hepatocytes.

Centrilobular Veins

Large 'holes' that the sinusoids converge on in the liver.

Portal Tracts

Three-part structures between liver lobules, including a branch of the hepatic artery and a bile-collecting duct.

Hepatocytes

Cells in the liver that store glycogen.

Sarcomeres

Regular arrangement of actin and myosin proteins.

Intercalated Discs

Transverse thickenings of the plasma membrane connecting cardiac muscle fibers.

Colloid

Extracellular suspension in the thyroid gland where hormones are stored.

Thyroid Follicle

Colloid and follicular cells together.

Pituitary Lobe (Anterior)

Consists of secretory epithelial cells enmeshed in a fine network of capillaries.

Pituitary Lobe (Posterior)

Resembles nerve tissue.