Human Anatomy Unit 1

HISTOLOGY In Anatomy Today Histology

• Study of tissues • Tissues = a group of cells performing a common function • Microscopic anatomy • Includes how different tissues are arranged to form organs and other structures

Ductus epididymis Tissue Sections

Longitudinal sections Transverse or cross section Tissue Sections 4 Tissue Types

• 4 Types of tissue – Epithelial tissue – Connective tissue – Nervous tissue – Muscle tissue • Characteristic Differences – Proportion of cells to matrix – Matrix composition – Cell function Epithelial Tissue

• Composition – One or more layers of closely adhering cells – Apical surface and basal surface – Rest on a basement membrane – Supported by connective tissues • Function – Cover organ surfaces – Form secretory tissue – Form ducts of glands Classification

• Criteria – Number of cell layers – Morphology of the surface cells • Two major categories – Simple (one layer) – Stratified (two or more layers) Cell Shape

• Squamous • Columnar

• Cuboidal • Acinar Simple Epithelia

• General – All cells touch basement membrane • Exception: Pseudostratified columnar • Categories – Simple squamous – Simple cuboidal – Simple columnar – Pseudostratified columnar Simple Epithelia Simple Squamous Epithelium Simple Cuboidal Epithelium Simple Columnar Epithelium

• Found in – Stomach – Small intestines – Colon – Appendix • Single layer of cells • Nuclei uniformly arranged Goblet Cell Epithelium

• Simple columnar epithelium with numerous goblet cells present • Goblet cells produce mucus • Found in: – Small intestine – Colon PCCE

• Pseudostratified ciliated columnar epithelium • Single layer of cells • Cilia present on the apical surface Cilia

Cilia are composed of microtubules and project from the apical surface. Function: to move things across the cell surface Stratified Epithelia

• General characteristics – Up to 20 or more cell layers – Named for shape of surface cells • Exception: transitional epithelium • Stratified squamous – Most common – Exfoliation – Keratinized tissue (cornified) – Nonkeratinized Stratified Squamous Epithelium

• Multiple layers of cells • Surface layer cells are squamous • Found in areas that experience friction – Epidermis – Vagina Stratified Cuboidal Epithelium

• Multiple layers of cuboid cells • Surface layer of cells are cuboidal • Found in – Large ducts of glands • Sweat glands • Pancreas Transitional Epithelium

• Found in secretory portions of the urinary system – Calyces – Ureters – Urinary bladder • Distensible tissue (stretches) • Epithelium “transitions” from cuboidal to almost squamous in appearance as tissue distends Connective Tissue

• Less cells, more ECF (ground substance) • Variable, widely distributed, most abundant • Three categories of mature tissue – Fibrous CT – Supportive CT (bone, cartilage) – Fluid CT (blood) Connective Tissue Functions

• Binds organs • Support • Protection – Physical – Immune • Movement • Storage • Heat production • Transportation Fibrous Connective Tissue: Components

• Cells • Fibers – Fibroblasts – Collagenous – Macrophage – Reticular – Leukocytes – Elastic – Plasma Cells – Ground substance – Mast Cells – Adipocytes Types of Fibrous Connective Tissue

• Loose CT • Dense CT – Lots of ground – Fiber is predominant substance component – Types – Types • Areolar • Dense regular • Reticular • Dense regular elastic • Adipose • Dense irregular Areolar Connective Tissue • Cells – All six types • Matrix – Predominately collagenous – Some elastic/reticular • General – Very vascular – Loosely organized – Varied – Underlies almost all epithelial tissue • These images are of mesentery Reticular Connective Tissue

• Reticular fibers and fibroblasts • Provides supporting framework (stroma), network or lattice • Found – Spleen – Lymph nodes – Thymus – Bone marrow Adipose Tissue

• Adipocytes most abundant cell type • Supported by areolar CT, reticular CT, blood vessels • Function: – Energy storage – Insulates – Supports – Cushions shock • White fat vs. Brown fat Dense Regular Connective Tissue

• “regular” arrangement of fibroblast and collagen fibers – Closely packed parallel collagen fibers + fibroblasts – Form bundles of collagen fibers • Found in tendons Dense Regular Elastic Connective Tissue

• Large amount of elastic fibers in parallel arrangement • Elastic fibers can stretch 1 ½ times their length and then recoil • Provides elasticity • Found – Ligaments – Large arteries – Bronchial tubes Dense Irregular Connective Tissue

• Collagen fibers in random arrangement + fibroblasts • Found – Reticular layer of dermis – Protective capsule around organs – Fibrous sheet around bones, etc. • Similar to areolar, but less “open” space Cartilage

• Flexible matrix • Avascular except when transforming to bone • External ear, tip of nose, larynx • Cells – Chondroblasts • Three types • secrete matrix – Hyaline – Chondrocytes – Elastic • trapped in lacunae – Fibrocartilage Hyaline Cartilage • Matrix – smooth, frictionless – mix of collagen, elastin, chondroitin (a glucosaminoglycan) • Cells – Cell nests • Usually covered by perichondrium – Dense irregular CT covering – inner layer produces new chondrocytes • Examples: – Costal cartilage – Nasal septum – C-ring cartilage of trachea – Fetal skeleton Elastic Cartilage

• Matrix – Web-like mesh of elastic fibers – Appearance of fur • Perichondrium always present • Examples: – Pinna of ear – Epiglottis Fibrocartilage

• Characteristics – Parallel collagen fibers – Rows of chondrocytes in lacunae – No perichondrium • Examples – Pubic symphysis – Intervertebral discs – Menisci of the synovial joints Supportive Connective Tissue: Bone Compact Bone

• No visible spaces • Dense calcified tissue • Found – External surface of all bone – Shafts of long bones • Tissue arranged into osteons – Concentric layers of matrix and osteocytes surrounding a central canal • Periosteum Spongy Bone

• Found – Heads of long bones – Middle layer of roofing bones of skull • Named for appearance • Tissue arranged into trabeculae (fusion of spicules) • Bathed in red marrow Fluid Connective Tissue: Blood

• Plasma + formed elements • Erythrocytes • Leukocytes – Neutrophils – Basophils – Eosinophils – Monocytes – Lymphocytes • Thrombocytes Nervous Tissue

• Excitable tissue • Function – Rapid communication • Cell types – Neurons – Neuroglia Muscular Tissue

• Contracts when stimulated • Three types – Skeletal – Cardiac – Smooth