Panniculus

Dr. Preethi chekuriMD DVL

Introduction

Occurs almost universally over the body surface, between the skin and deep fascia

Absent from eyelids and male genitalia

It varies in thickness with the race, age, sex, endocrine and nutrtional status

In a normal person, fat constitutes 10% of body weight

Functions

Acts as an insulating layer

Protective cushion

Thermogenesis

Store of readily available energy

Major endocrine organ

Provides support and has cosmetic function (contours of face)

Embryology

Pre – adipocyte appears in the mesenchyme at 14th week of fetal life

Pre – adipocyte terminally differentiate into either brown adipocyte or white adipocyte

Development of brown fat begins at the 20th week of gestation, reaches maximum at birth

Brown fat

It is multilocular and metabolically very active with many mitochondria

Surrounded by a greater capillary network than white fat ( partly responsible for the brown colour), such that heat can be rapidly tranferred into the circulation

Most prominent in neck and upper thorax of fetus

Adults have supraclavicular areas of brown fat

Histology of adipocytes

Have a diameter upto 100 microns

Mature fat cell has a characteristic signet ring appearance, because the oval nucleus is displaced to a side by a single, large, intracellular, fat containing vacuole, which is surrounded by perilipin

Arranged in lobules, which are separated by interlobular septa

Each lobule consists adipocytes, stromavascular tissue being macrophages, fibroblasts, mast cells, pericytes, endothelial cells and pre-adipocytes

Blood, nerve and lymph supply

BLOOD - Fat tissue has an abundant blood supply, each lobule being supplied by a terminal arteriole running along the septa

Then breaks up to form capillaries

LYMPH - Also contains a rich lymphatic plexus

These lymph vessels penetrate deep fascia and drain into regional lymph nodes

NERVE - Innervated by noradrenergic fibres of sympathetic nervous system and para sympathetic fibres

Adipogenesis It refers to the recruitment from multipotent

stem cells in the mesenchyme and stromavascular tissue, and proliferation of pre adipocytes followed by their differentiation into mature fat cells

-Glucocorticoids -growth hormone and -insulin, stimulate cells to terminally differentiate, but after a certain size, growth occurs through hyperplasia rather than hypertrophy

Energy homeostasis

Catabolism and anabolism of fat depends on -nourishment, endocrine and nervous activity

Insulin inhibits hydrolysis and breakdown of triglycerides, conserving the energy store

Adipose tissue in vitro has a metabolic rate similar to a kidney and half that of liver

Outline of lipogeneis in an adipocyte

Fat as an organ

Apart from the subcutaneous fat, 20% of fat tissue occurs internally, in mediastinal and retroperitoneal tissues, mesentry, marrow and other individual organs including blood vessels

In view of the recent obesity epidemic, increase in the upper body and visceral fat are associated with an increase cardiovascular and metabolic risks

Fat as an endocrine organ

Adiponectin

Protein with structural similarity to collagen and C1q

Has autocrine/paracrine effects locally and endocrine effects distally

Promotes pre adipocytes to become mature fat cells with increase in size

Serum adiponectin levels are lower with weight gain and higher with weight loss

Also exerts anti inflammatory properties

Leptin

Adipokine involved in energy homeostasis

Structural homology similar to other cytokine proteinssuch as TNF alpha and IL-6

Exerts main effect via satiety centres

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