**Neuroanatomy**

I extend my gratitude to the authors and the editorial and secretarial staff who worked with much devotion and enthusiasm to publish this volume. I wish that it might be one more step

**Stavros J. Baloyannis MD, PhD**

Thessaloniki, Macedonia, Greece **Dr. Jan Oxholm Gordeladze Ph.D** Department of Biochemistry Institute of Basic Medical Science University of Oslo, Norway

Professor Emeritus Aristotelian University

for further fruitful research activity in the immense field of the human hypothalamus.

VIII Preface

**Chapter 1**

**Provisional chapter**

**Anatomy and Function of the Hypothalamus**

**Anatomy and Function of the Hypothalamus**

DOI: 10.5772/intechopen.80728

The hypothalamus is a small but important area of the brain formed by various nucleus and nervous fibers. Through its neuronal connections, it is involved in many complex functions of the organism such as vegetative system control, homeostasis of the organism, thermoregulation, and also in adjusting the emotional behavior. The hypothalamus is involved in different daily activities like eating or drinking, in the control of the body's temperature and energy maintenance, and in the process of memorizing. It also modulates the endocrine system through its connections with the pituitary gland. Precise anatomical description along with a correct characterization of the component structures is

At the end of the fourth week of embryological development, the neural tube is organized in primary vesicles: the forebrain vesicle or prosencephalon, the midbrain vesicle or mesencephalon, and the hindbrain vesicle, also called rhombencephalon. Prosencephalon further divides into two secondary vesicles, the telencephalon that will form the cerebral hemispheres and the diencephalon which gives rise to the diencephalon. Mesencephalon forms the midbrain, structure involved in the processes of vision and hearing. The hindbrain vesicle or rhombencephalon divides in metencephalon, which further forms the pons and the cerebellum and the

Embryological concepts regarding the development of the hypothalamic region are over 100 years old. Since Herrick [1] first proposed the columnar model of the forebrain organization,

> © 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

© 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use,

distribution, and reproduction in any medium, provided the original work is properly cited.

Miana Gabriela Pop, Carmen Crivii and

Miana Gabriela Pop, Carmen Crivii and

http://dx.doi.org/10.5772/intechopen.80728

Additional information is available at the end of the chapter

Additional information is available at the end of the chapter

essential for understanding its functions. **Keywords:** anatomy, structure, function

myelencephalon that forms the medulla.

**1. Embryological development of the hypothalamus**

Iulian Opincariu

Iulian Opincariu

**Abstract**

#### **Chapter 1 Provisional chapter**

#### **Anatomy and Function of the Hypothalamus Anatomy and Function of the Hypothalamus**

DOI: 10.5772/intechopen.80728

Miana Gabriela Pop, Carmen Crivii and Iulian Opincariu Miana Gabriela Pop, Carmen Crivii and Iulian Opincariu

Additional information is available at the end of the chapter Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/intechopen.80728

#### **Abstract**

The hypothalamus is a small but important area of the brain formed by various nucleus and nervous fibers. Through its neuronal connections, it is involved in many complex functions of the organism such as vegetative system control, homeostasis of the organism, thermoregulation, and also in adjusting the emotional behavior. The hypothalamus is involved in different daily activities like eating or drinking, in the control of the body's temperature and energy maintenance, and in the process of memorizing. It also modulates the endocrine system through its connections with the pituitary gland. Precise anatomical description along with a correct characterization of the component structures is essential for understanding its functions.

**Keywords:** anatomy, structure, function

## **1. Embryological development of the hypothalamus**

At the end of the fourth week of embryological development, the neural tube is organized in primary vesicles: the forebrain vesicle or prosencephalon, the midbrain vesicle or mesencephalon, and the hindbrain vesicle, also called rhombencephalon. Prosencephalon further divides into two secondary vesicles, the telencephalon that will form the cerebral hemispheres and the diencephalon which gives rise to the diencephalon. Mesencephalon forms the midbrain, structure involved in the processes of vision and hearing. The hindbrain vesicle or rhombencephalon divides in metencephalon, which further forms the pons and the cerebellum and the myelencephalon that forms the medulla.

Embryological concepts regarding the development of the hypothalamic region are over 100 years old. Since Herrick [1] first proposed the columnar model of the forebrain organization,

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

the anatomical description was accepted *per se* and very few research papers have questioned its validity.

Only on the inferior surface of the brain, the hypothalamus can be visualized from the optic chiasm and the anterior perforated substance anteriorly to the posterior cerebral peduncles of the midbrain and the mammillary bodies, dorsally (**Figure 1**). The mammillary bodies are small, round white-matter structures that belong to the limbic system. They are involved in memory due to their connections with the hippocampal region and also in maintaining the sense of direction [7]. The hypothalamus is limited laterally by the optic tracts in their direction toward the lateral geniculate bodies, an important relay of the optical pathway. Inside the delimited area on the exterior surface of the brain, a small prominence, called tuber cinereum or infundibulum connects the hypothalamus with the posterior lobe of the underneath pituitary gland. The pituitary or the hypophyseal gland is located at the base of the brain, in a

Anatomy and Function of the Hypothalamus http://dx.doi.org/10.5772/intechopen.80728 5

The pituitary gland is a three-lobe structure: anterior, posterior and intermediate lobe, with

The anterior lobe, pars anterior, or adenohypophysis is derived from the anterior wall of Rathke's pouch, an ectodermal structure that also forms the primitive oral cavity and the pharynx [8]. The anterior gland contains a heterogeneous cellularity that synthesized and secreted hormones in the blood stream: the majority of the cells are somatotrope cells that produced the human growth hormone (hGH) or somatotropin hormone (STH), a peptide that promotes growth in childhood. The production of the somatotropic hormone is under the control of the hypothalamic growth-releasing hormone (GRH) produced by the arcuate nucleus. The next hormones produced in high quantity by the anterior gland of the hypophysis are the corticotrope ones (adrenocorticotropic hormone—ACTH, melanocyte-stimulating hormone—MSH, and beta-endorphins). This group of hormones is under the control of the hypothalamic corticotropin-relasing hormones (CRHs) derived from the paraventricular nuclei. In smaller percentages, the adenohypophysis has population of cells that produced

depression of the sphenoid bone called the sella turcica.

**Figure 1.** Inferior surface of the brain with hypothalamic visualization at this level.

**2.1. The hypothalamus—hypophyseal complex**

different embryological origin.

The columnar morphologic model is based on the division of the forebrain in functional longitudinal units, placing the telencephalon in the most rostral region and the diencephalon caudally, in between the telencephalon and the midbrain, while the hypothalamus if formed from the ventral most part of the diencephalic vesicle [2].

In the last decades, mapping of the genes involved in hypothalamic development allowed the identification of a disparity between the morphological, classic boundaries of this region and the molecular ones. According to Puelles' Prosomeric model [3], the initially proposed longitudinal axis of the brain is bent due to the first mesencephalic flexure of the embryo. This condition puts the diencephalon rostrally between the telencephalon cranially and the midbrain caudally and sets the hypothalamus independent from the diencephalon as a distinct posterior part of the forebrain [2, 3].

An important role in hypothalamic development is assigned also to the presence of specific signaling centers (Wingless-Int protein family–Wnt, Hedgehogs family–Hh, and Bone morphogenetic family–FgF) that modulates cell proliferation and neurulation [4].
