Lecture 6 Adipose tissue بسم الله الرحمن الرحيم Histology Lecture 6 Adipose tissue

Adipose Tissue A kind of connective tissue with many adipocytes Forms one of the largest “organs” of body 15-20% of body weight in men 20-25% of body weight in women Over 2 times as much stored energy as glycogen Subcutaneous adipose shapes body Shock absorber in soles of feet and palms Fills space between organs

Types of Adipose Tissue Yellow, White or unilocular cells with one large fat droplet in cytoplasm Brown or multilocular cells with numerous smaller lipid droplets in cytoplasm and many mitochondria

Unilocular Adipose Tissue White to dark yellow depending on diet Most common form in adults Cells 50-150 micron diameter Nuclei eccentric and flattened Lipid droplet has no membrane Heavily vascularized Cell number constant after early postnatal period

Unilocular Adipose Tissue

Histogenesis

Multilocular Adipose Tissue Fat cells store fat in multiple droplets Brown fat, color due to vascularization and many mitochondria, Central nucleus Has a lobular organization like glands Production of body heat by many mitochondria In human neonate, produces heat

Brown or multilocular adipose tissue

Brown or multilocular adipose tissue

Histology Lecture 7 Cartilage and Bone

Cartilage It supports soft tissues (nose, ear, trachea) A kind of connective tissue with very firm extracellular matrix It supports soft tissues (nose, ear, trachea) Responsible for development and growth of long bones Joint

Different Forms of Cartilage There is three different kinds of cartilage: Hyaline cartilage (collagen type II) Elastic: (elastic fibers,and collagen type II) Fibrocartilage: (type I collagen)

Hyaline Cartilage Collagen type II

Perichondrium Vascular sheath(dense irregular connective tissue) Inner cellular layer (chondrogenic cells that undergo division and differentiate into chondroblasts) Outer fibrous layer Articular cartilage lacks perichondrium,

Hyaline Cartilage Glassy blue-grayish in color In embryo it serves as skeleton joint surfaces, epiphyseal plate, nose, larynx, trachea, bronchi, ends of ribs adjacent to sternum Amorphous ground substance Pericellular capsule (1-3 µm) just around the lacuna

Hyaline Cartilage matrix Chondrocyte Isogenous groups of chondrocytes

Appositional growth

Cartilage Growth Interstitial growth: mitotic division of existing chondrocytes forming isogenous groups which are produce matrix and enlarging cartilage from within Appositional growth: differentiation of new chondroblasts from chondrogenic cells located in inner layer of perichondrium and adding matrix to periphery of cartilage

Interstitial growth

Elastic Cartilage Location: auricle of ear, external auditory canal, eustachian tube, epiglottis, cuneiform cartilage of larynx It is similar to hyaline cartilage, but with many branching elastic fibers Yellow in colour and more opaque than hyaline cartilage Chondrocytes are more abundant and larger but matrix is less than hyaline cartilage Perichondrium is also rich in elastic fibers

Elastic cartilage Elastic fibers Large Chondrocytes

Fibrocartilage Location: intervertebral disks, tendon and ligament attachments to bone, pubic symphysis, and articular disk Usually merges with adjacent dense connective tissue Fibrocartilage matrix is scant (rich in chondroitin and dermatan sulfate), and exhibit bundles of type I collagen which stain acidophilic It has not perichondrium

Fibrocartilage Chondrocyte Matrix Collagen bundle

Department of Histology دكتر محمد هادي بهادري